A quick update and where to check out some of my latest writing elsewhere on the web

As you may have noticed, it has been a while since I have posted on this blog. Rest assured, I have a ton of great content in the works.

But what has been keeping me too busy to post and up at night? Well, Baby #3 for starters. (Now 8 months! How time flies… or with a new baby, how it passes in slow motion and sudden leaps.)

And in my stolen moments (read:naps) I have been writing content for a company called BloomLife. BloomLife makes a contraction tracker, just like those used in a hospital but for at home use. It syncs with your phone and lets you know if you are experiencing contractions, how strong they are, and how long they last.

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Baby #3 and her big sister. None of us were quite ready to wake up the morning this picture was taken. Yet there we were, up.

Many of my posts for Bloom will be of interest to my readers, so I wanted to share them with you here. Hop on over and check them out!

  • Prenatal Genetic Testing and Screening. My take on the new kid on the prenatal genetic screening block, Non-Invasive Prenatal Testing (NIPT) and why it needs to be offered to all women, not just women over 35.
  • Stalled Labor. My first labor was going gangbusters until I arrived at the hospital, where it swiftly ground to a halt. This is a common birthing experience. At the time, I blamed the slowdown on stress, but another unexpected culprit may have been to blame: those glaring florescent hospital lights. Here’s more on how humans evolved to labor at night, and why laboring women would be wise to dim those darn lights!
  • Exercise during pregnancy. Should you avoid starting a new exercise program while pregnant? Do you need to keep your heart rate below 140? Will lifting weights prompt preterm labor? Contrary to what you may have heard, the answer to all of these questions is an emphatic NO. I discuss the all these exercise myths here, and talk about the latest research and recommendations on exercise for pregnant women.
  • Natural Remedies for Group B Strep. Anywhere from quarter to a third of pregnant women test positive for Group B Strep (GBS) in their third trimester. In the U.S., this means receiving IV antibiotics during labor, to prevent early-onset Group B Strep, a serious but rare infection that occurs when a newborn contracts GBS during birth. But nobody wants to receive antibiotics if they can avoid it, especially during birth, when mom needs to pass her microbiome–a diverse collection of healthy bacteria and other microbes–to her baby. So, is there anything you can do to avoid testing positive? I talk about the research on vinegar rinses, yogurt squatting, and probiotics here.

What I’ve Been Doing the Last Few Weeks

It’s been awhile since I’ve posted on this blog, so I wanted to give my readers a bit of an update on what I’ve been up to these past couple of months.

Mostly I’ve been away because of some good news: I’m expecting our third child, a girl, coming sometime in October!

Continue reading What I’ve Been Doing the Last Few Weeks

The Middlemiss Study Tells Us Nothing About Sleep Training, Cry-It-Out, or Infant Stress

Last week, I wrote a post about sleep training and stress, in which I argued that everything we know about stress suggests that sleep training is not harmful.

In response, some people objected that sleep trained babies continue to experience elevated cortisol and significant distress, even after they have stopped crying. In their view, sleep training teaches babies that crying does not help. They haven’t learned to self-soothe or to fall asleep on their own, they’ve simply given up.

What a heartbreaking thought. And one that surely strikes fear in the heart of many parents.

So it’s important to realize that this claim comes from a single small and deeply flawed study of 25 babies, led by Wendy Middlemiss, a researcher at the University of North Texas’s College of Education.

Continue reading The Middlemiss Study Tells Us Nothing About Sleep Training, Cry-It-Out, or Infant Stress

Critics of Cry-It-Out Fundamentally Misunderstand How Stress Affects the Brain

Because whether or not to sleep train can be such a fraught decision for new parents, I wanted to share my sleep training story, and to explain why, given everything we know about stress, the argument that sleep training causes long-term harm doesn’t hold water.

Sleep Training My Son

When my son was 4.5 months old, I decided to sleep train him. Even by baby standards, my son was not much of a sleeper. He’d snooze for at most 4 or 5 hours, and then wake up every hour like clockwork, wanting to nurse but not wanting milk, popping on and off my breast and screaming in frustration.

I had gone back to work a month earlier, so napping to catch up on sleep was out of the question. Worse, I was commuting an hour to the office each way.

By then, I had reached the end of my sleep deprivation rope. I was so tired I could barely string two thoughts together. I had to coach myself through even mundane tasks like checking out at the grocery store. Say hello to the cashier. Take out your credit card. Pick up the grocery bags. Leave.

I was terrified every time I got into my car to head to work that I would nod off at the wheel and kill someone, quite possibly myself. I joked with coworkers that driver’s licenses should be temporarily suspended for new parents, but the situation really wasn’t funny.

So there I was the first night of sleep training, dripping sweat as I listened to my son’s cries. Minutes ticked by, each seeming longer than the last. I pondered whether the Ferber method included soothing every five minutes just so that you would realize only five minutes had passed.

But I was determined to stick this out, to get it done. Doing it halfway was worse than not doing it at all, I reminded myself over and over. If I were to give in, I could teach my son that crying for 30 minutes was what it took to get mommy to pick him up.

That night, he woke two more times, but never again cried more than 15 minutes. The next night, he cried for 10 minutes at bedtime, conked out, and slept until morning. That morning we greeted each other with a smile, and for the first time since his birth, I really felt like smiling at his freshly woken little face.

Although by all appearances, sleep training went well for us, some critics of cry-it-out methods would contend that I was an inadequate parent who had permanently harmed my son by leaving him alone to cry.

The Cry-It-Out Controversy

“An emotionally available parent would probably not let their baby cry it out,” claims Dr. Teti, a researcher at Penn State.

Dr. Narvaez writes in Psychology Today:

“Letting babies get distressed is a practice that can damage children and their relational capacities in many ways for the long term. We know now that leaving babies to cry is a good way to make a less intelligent, less healthy but more anxious, uncooperative and alienated persons.”

When someone tells you that you have permanently damaged your child, it’s hard to shake off, no matter how much happier you and your baby seem once you start getting some solid rest.

Thankfully, as someone who has studied the effects of chronic stress in animals and in people, I knew that claims like Dr. Narvaez’s are not supported by data and instead rest on a fundamental misreading of stress research.

Studies on Cry-It-Out

Studies involving cry-it-out methods find no ill long-term effects for babies, and big benefits for parents. In one study, rates of depression in mothers dropped from 70% to 10% after sleep training.

Critics of cry-it-out methods argue that these studies are flawed–they don’t have the right measures of harm, they fail to determine whether the parents actually used cry-it-out methods to sleep train their babies, and they rely on parents’ reports instead of observation.

Admittedly, some of these criticisms of sleep training research are fair. Sleep training research is hard to do, especially since researchers can’t exactly force parents to sleep train little Johnny, or prevent parents from doing so.

That said, there’s no evidence in humans–none–to support the view that sleep training is harmful. If there were, we’d have heard about it.

So what the critics of cry-it-out argue, really, boils down to this: They know that sleep training is harmful, because they know stress is harmful to babies.

The problem with that argument? All stress is not created equal. We were designed to handle short-term stress. Where we humans, and other animals, run into trouble is when stress becomes chronic.

Short-Term Versus Chronic Stress

In terms of their effects, the difference between short-term and chronic stress is one not of degree, but of kind. Short-term stress enhances memory; chronic stress impairs it. Short-term stress boosts the immune system; chronic stress weakens it.

(Seeing short-term and chronic stress as fundamentally different is not just my own heterodox personal take. This is the view of people who study stress for a living, including the renowned stress neuroscientist and primatologist Robert Sapolsky, professor of Neurology at Stanford University, who writes extensively about this key distinction in his excellent book, Why Zebras Don’t Get Ulcers. The American Academy of Pediatrics emphasizes this distinction in its statement on early life stress. And the Harvard statement on child development, cited by Dr. Narvaez herself in her Psychology Today piece, makes a point of distinguishing between short-term and long-term stress.)

The Effects of Stress in Early Life

Short-term stress mobilizes us for action–the classic fight-or-flight response. Adrenaline and cortisol pump through our veins; our bodies brim with energy; and mentally we become hyper-focused.

But these short-term adaptations are harmful when switched on for too long, especially when we are young. Scores of animal and human studies show that early life stress, such as severe early social deprivation, leads to long-term changes in the brain, cognitive and social problems, and heightened susceptibility to anxiety, depression, and drug abuse in adulthood. Chronic stress is toxic.

But from this can we conclude that all early stress, even short-term stress, is harmful?

No. Absolutely not. In studies of short-term stress early in life, occurring within the larger context of a close caregiver-infant relationship, none of these ill effects are observed.

In fact, young monkeys exposed to early short bouts of stress, such as brief periods of separation from their mothers, become more resilient to future stresses. They are less anxious and have less extreme physiological reactions to stress later in life. This phenomenon is so consistent that researchers have labelled it stress inoculation.

My Take

So where does that leave us? A little stress, even in infancy, is fine, if not beneficial, but too much for too long is very, very bad.

Do we know exactly where sleep training fits in this spectrum? Just how much stress does a baby experience during cry-it-out?

The short answer is that we don’t know for certain. Everything we do know, however, suggests that this amount of stress, in the context of a warm, loving family, is just fine.

To see why, let’s return for a second to the American Academy of Pediatrics statement on early life stress, which provides examples of the types of stress children can withstand, provided they occur within a broader context of loving, supportive relationships. These include “the death of a family member, a serious illness or injury, a contentious divorce, a natural disaster, or an act of terrorism”. By comparison, sleep training seems pretty mild.

But I would go further. I believe that sleep training is not only not harmful, it is beneficial. Successful sleep training can decrease depression and chronic stress in the parents, and this benefits parents and their babies. Unlike sleep training, having a depressed mother during early childhood has been shown, repeatedly, to be linked with worse long-term outcomes for children.

Which brings me to what I find most troubling about the claims of sleep training opponents: Their zero-sum take on parenting. Worrying about your own sleep needs is selfish, they not so subtly imply. Any time you fail to put your baby’s needs before your own, you are potentially doing him harm.

What a narrow, cramped view of parenthood.

No one would ever dispute that parenthood entails enormous sacrifices, especially when your children are young and their need for you feels so endless and all-consuming.

But I think that because parenthood, and motherhood in particular, is so often judged in terms of self-sacrifice, we tend to forget that a primary job for parents is to be strategic.

As parents, we must weigh short-term costs against long-term harms, because our children cannot. We have to consider the risk of a few nights of stress and unmet needs against the risk of a car accident or job loss, and against the serious physical and emotional toll of chronic sleep deprivation on the entire family.

We can forget, too, that the parent-child relationship is one not only of sacrifice but also of profound mutual benefit. You being a whole, fulfilled individual with a solid relationship with your partner, meaningful social ties, and a sense of purpose enriches your world and your child’s world. You being a well-rested, healthy, and happy parent is good for you and good for your child.

References

Ashokan A, Sivasubramanian M, Mitra R. Seeding Stress Resilience through Inoculation. Neural Plasticity. 2016;2016:4928081. doi:10.1155/2016/4928081.

Center on the Developing Child (2010). The Foundations of Lifelong Health Are Built in Early Childhood. Retrieved from www.developingchild.harvard.edu.

Crofton EJ, Zhang Y, Green TA. Inoculation Stress Hypothesis of Environmental Enrichment. Neuroscience and biobehavioral reviews. 2015;0:19-31. doi:10.1016/j.neubiorev.2014.11.017.

Darcia Narvaez. Dangers of “Cry-It-Out”: Damaging children and their relationships for the longterm. Psychology Today. 2011.

Fenoglio KA, Brunson KL, Baram TZ. Hippocampal neuroplasticity induced by early-life stress: Functional and molecular aspects. Frontiers in neuroendocrinology. 2006;27(2):180-192. doi:10.1016/j.yfrne.2006.02.001.

Gunnar M. Reactivity of the Hypothalamic-Pituitary-Adrenocortical System to Stressors in Normal Infants and Children. Pediatrics. September 2, 1992;90(3):491.

Hsiao YM, Tsai TC, Lin YT, Chen CC, Huang CC, Hsu KS. Early life stress dampens stress responsiveness in adolescence: Evaluation of neuroendocrine reactivity and coping behavior.Psychoneuroendocrinology. 2016 May;67:86-99.

Lyons DM, Parker KJ, Schatzberg AF. Animal Models of Early Life Stress: Implications for Understanding Resilience. Developmental psychobiology. 2010;52(5):402-410. doi:10.1002/dev.20429.

Mindell JA, Kuhn B, Lewin DS, Meltzer LJ, Sadeh A; American Academy of Sleep Medicine. Behavioral treatment of bedtime problems and night wakings in infants and young children. Sleep. 2006 Oct;29(10):1263-76.

Parker KJ, Buckmaster CL, Sundlass K, Schatzberg AF, Lyons DM. Maternal mediation, stress inoculation, and the development of neuroendocrine stress resistance in primates.Proceedings of the National Academy of Sciences of the United States of America. 2006;103(8):3000-3005. doi:10.1073/pnas.0506571103.

Sánchez MM, Ladd CO, Plotsky PM. Early adverse experience as a developmental risk factor for later psychopathology: evidence from rodent and primate models. Dev Psychopathol. 2001 Summer;13(3):419-49.

Sanchez MM, McCormack KM, Howell BR. Social Buffering of Stress Responses in Nonhuman Primates: Maternal Regulation of the Development of Emotional Regulatory Brain Circuits. Social neuroscience. 2015;10(5):512-526. doi:10.1080/17470919.2015.1087426.

Morning Sickness & Miscarriage: How Much Does Nausea Lower Your Risk?

For most women, the first trimester is brutal. About a week or two after you find out you’re pregnant (two lines!), you start to feel exhausted, queasy, and like you might throw up at any moment.

You are not alone. Somewhere between 70-80% of pregnant women experience nausea during their first trimester. About half of women also experience vomiting.

Nausea tends to worsen with each subsequent pregnancy, and become more likely to persist into the second trimester. Your race and ethnic background also matter: White women are more prone to nausea than Black and Asian women, and Black women are more likely to have nausea that starts after the first trimester.

While morning sickness is awful, it does come with a significant silver lining: Nausea tends to signals a healthy pregnancy. Women with nausea have a much lower risk of miscarrying and–as is less widely known–a lower chance of preterm labor.

Morning Sickness and Risk of Miscarriage

For those experiencing nausea, the risk of miscarriage is not just a tiny bit lower, but a huge whopping amount lower than that of women with no nausea.

Woman with nausea have only a third of the chances of a miscarriage as other women. The effect is even stronger among women of “advanced maternal age”–that is, over 35: They have only about a fifth the odds of a miscarriage as other women over 35 with no nausea.

Despite these large effects, if you do not have any nausea, do not panic. A lack of morning sickness does not necessarily imply an impending miscarriage. A lucky 20-30% of pregnant women never experience any morning sickness but give birth to perfectly healthy babies.

Timing also matters: Before 7 weeks, a lack of nausea does not predict miscarriage risk.

Name Calling: Nausea and Vomiting of the Pregnancy (NVP) Versus Morning Sickness

Before we dig into the details, let’s get our terminology straight: Although nausea and vomiting during pregnancy are often referred to as “morning sickness”, most medical professionals prefer the term nausea and vomiting of the pregnancy (NVP). “Morning” sickness, they feel, is misleading.

As many first-time mums-to-be discover to their dismay, nausea often lasts all day long, not just in the morning, . In fact, in one study, less than 2% of women with “morning sickness” had nausea and vomiting only in the morning. Other studies have put the percentage of morning-only suffers at 14%.

The Onset of NVP and Miscarriage Risk

On average, women start to experience NVP 39-40 days after their last menstrual period, around the middle of the 5th week of pregnancy (counting from a woman’s last menstrual period), Symptoms typically begin to ease by around 12 weeks and usually disappear completely by 20 weeks.

That said, 39 days is only the average day of symptom onset. For an unlucky 10% of women, NVP begins much earlier, before they even miss their period. For the 70-80% women who will experience any morning sickness, though, that all day queasy, on-a-winding-road-with-a-bad-hangover feeling will have started by the end of your 8th week of pregnancy, or 7 weeks after conception.

So it’s only in 9th week of pregnancy that a lack of morning sickness predicts higher chances of a miscarriage, according to a prospective study that tracked symptoms of 2407 pregnant women from early in their first trimester.

Line chart shows chances of miscarriage peak in week 8 among those without nausea and vomiting, and remain higher until 13 weeks.

When a women’s nausea begins does not matter. Women who had nausea starting at 4 weeks or at 7 weeks have about the same low chances of a miscarriage.  Similarly, the end of nausea does not appear to make much of a difference. By 12 weeks, the risk of women without nausea drops back down to that of women with nausea.

What Exactly Is Morning Sickness and Why Does It Predict Miscarriage?

So we know that NVP is strongly related to the chances of a healthy, successful pregnancy. But why?

NVP is one of pregnancy’s great mysteries. We don’t know why it occurs. We don’t even know what hormones or other biological changes causes NVP. And we don’t know whether NVP serves a a specific adaptive purpose, as some evolutionary theorists have proposed, or whether it is just an unpleasant side effect of hormonal shifts during early pregnancy.

Rapid rises in hormones like estrogen, progesterone, and human chorionic gonadotropin (HCG) are the prime suspects. So far, though, the evidence for their role is only circumstantial.

Consider HCG, the hormone with the most evidence for a role in NVP. HCG levels in a woman’s blood rises rapidly during the early weeks of pregnancy, doubling every 2 to 3 days. Its concentration peaks sometime between 8-10 weeks of pregnancy.

HCG’s rise corresponds when NVP symptoms are usually at their worst. Conditions which cause high HCG levels like Down’s Syndrome, molar pregnancies, and twin pregnancies are often linked with severe NVP.

That said, HCG levels do not reliably distinguish women with and without NVP, and no one understands why, at a biological level, HCG would induce nausea.

Another potential suspect is pregnant women’s bloodhound-like sense of smell. In a small study of 9 women who had congenital anosmia–they were born with without the ability to smell–only 1 of the 9 suffered from NVP during pregnancy, a rate substantially lower than the usual 4 out 5.

Despite our poor understanding what causes nausea biologically, few researchers believe that a lack of symptoms causes miscarriage.

Why not? For one, treating NVP does not lead to worse pregnancy outcomes. If anything, the opposite is true: Women who take anti-nausea medications have better outcomes, on average, than women who do not take anti-nausea medications–not because treatment itself improves outcomes, but because severe NVP severe usually indicates a healthy placenta.

The Bottom Line

For everyone discretely ducking out of meetings to quietly vomit in the ladies room, there is light at the end of the tunnel. And knowing that your sickness likely means that your pregnancy may provide some comfort. I always clung to that fact as I was clinging to the toilet bowl after dinner.

But please do not think I am trying to minimize the dreadfulness of nearly non-stop nausea.

Nausea and vomiting are more than a simple inconvenience. Women with NVP, even those with so-called “mild” NVP accompanied by little or no vomiting, commonly report decreased productivity at work, taking sick time, strained relationships with their partners, and heightened anxiety and depression.

For around 1 in 100 pregnant women, NVP is life-threatening. Women with especially severe NVP, a condition known as hyperemesis gravidarum, suffer from such severe nausea that they cannot keep food or water down, and require hospitalization. In the U.S. each year, around 50,000 women are hospitalized for severe NVP.

If you are vomiting several times a day or unable to keep fluids down, seek medical help right away. Early treatment may help prevent NVP from becoming dangerously severe.

Light Drinking During Pregnancy: 7 Things You Need to Know

Last year, the CDC ignited a firestorm of criticism by stating that women should “stop drinking alcohol if they are trying to get pregnant or could get pregnant”, and–because an estimated 50% of pregnancies in the U.S. are unplanned–any woman who drinks alcohol should use birth control.

“Its [the CDC’s] underlying message was unmistakable: Women should consider themselves first a vessel for human life and make decisions about their health and behavior based on that possibility,” Rebecca Ruiz wrote at Mashable, in a typical reaction.

The (completely understandable) outrage at the CDC’s tone-deaf and condescending messaging has, unfortunately, drowned out information on the key question for many pregnant women: Is any amount of alcohol during pregnancy okay? And are there times when it should be absolutely avoided?

We all know that heavy drinking and binge drinking are harmful during pregnancy. Fetal alcohol syndrome, caused by heavy drinking during pregnancy, affects an estimated 2 to 7 children out of 1000. Another 2 to 7% of U.S. children are thought to suffer milder forms of cognitive impairment due to alcohol exposure in the womb.

But what about light drinking, a champagne toast or an occasional glass of wine at dinner? Women–pregnant, pre-pregnant, and otherwise–receive conflicting advice about the safety of light drinking.

Economist Emily Oster, in her bestselling pregnancy advice book Expecting Better, says pregnant women can be comfortable with “1 to 2 drinks a week in the first trimester” and one drink daily afterward, a stance she continues to stand behind.

Many doctors also greenlight the occasional drink, as Ruth Graham of Slate notes: “Many doctors seem perfectly comfortable with moderate alcohol consumption in the late stages of pregnancy. When I told my doctor that I was enjoying a glass of wine per week in my third trimester, she didn’t bat an eye.”

The CDC, on the other hand, maintains that no amount of drinking is safe.

“Any drinking is going to put your child at risk,” according to Clark Denny, a CDC epidemiologist. “You should not drink if you are pregnant, are considering getting pregnant or even if you could possibly get pregnant.”

Other countries, like the U.K. and France, that once gave less stringent advice–pregnant women should not exceed 1-2 drinks per week–now state no amount of drinking is safe, and that women who are pregnant or trying to conceive should abstain entirely.

At the heart of this debate is the research itself. So, what do we actually know about light drinking during pregnancy?

Let’s start with alcohol and the risk of miscarriage.

  1. Light drinking, the equivalent of 1-2 drinks per week, during the first trimester, boosts the odds of a first trimester miscarriage by about 30%, and the odds of a early second trimester miscarriage (between 13-16 weeks) by about 70%, according to a large study of over 90,000 pregnancies in Denmark. The risk rose with greater intakes. Drinking 4 or more drinks per week during the first trimester more than doubled the odds of a miscarriage. A U.S. based study found that women who drink 2 times per week in their first trimesters had a 25% chance of miscarriage, compared to a 14% chance for those who abstained. Other studies also find a higher risk of miscarriage for light drinkers (see here and here).

Does this mean that light drinking early in pregnancy causes miscarriage? Unfortunately, we cannot say for sure. Experimental studies in humans are impossible, so there are a lot of unknowns.

For one, some women may understate how much they actually drank during pregnancy, so the apparent rise in miscarriage could actually stem from moderate to heavy, rather than light, drinking.

Women who drink heavily during pregnancy often also smoke or have partners who smoke, and are more likely use drugs, receive worse prenatal care, live in poverty and experience extreme chronic stress–all of which can raise the risk of miscarriage and cognitive problems in their children, and any and all of these factors could exacerbate the toxic effects of alcohol on the fetus.

Poor nutrition and smoking seem to worsen the effects of alcohol. This makes sense, as alcohol lowers how much nourishment reaches the fetus.

Women who drink alcohol during their first trimester may have less nausea. (I for one could not get near alcohol in my first trimester, as much as I might, after a long day of nausea and chasing after a toddler, desire a drink.) Although about 25% of women do not experience nausea during pregnancy, an absence of nausea is linked with an increased risk of miscarriage, probably because poorly developing pregnancies produce fewer symptoms.

And finally, the problem may not arise from drinking during early pregnancy but from drinking before pregnancy.

2. Drinking alcohol may lower the chances of pregnancy, and increase the chances of miscarriage, by causing chromosomal abnormalities in the egg before ovulation. Alcohol has been shown to impair meiosis, the critical two-step cell division in maturing egg follicles, leading to chromosomally abnormal eggs. Chromosomal abnormalities account for over half of first trimester miscarriages. Worse, because eggs take several months to fully mature, even drinking in the months before conception could be harmful.

How much alcohol do you have to drink to harm your eggs? Again, we don’t have a good answer. The degree of harm likely depends on a lot of other things, like your age, your overall fecundity, your alcohol tolerance, how much alcohol you drink, and when you drink relative to critical phases in the egg’s development.

Clearly, even formerly heavy drinkers go on to have chromosomally normal and perfectly healthy pregnancies, so the effect is not absolute. The increase in chromosomal abnormalities is probably most problematic for couples already suffering from fertility issues. Among couples undergoing IVF, for instance, drinking appears to lower their chances of pregnancy.

Because the human data are limited, we have to turn to animal models. In one study using monkeys, the equivalent of binge drinking (4-5 drinks at a sitting) twice a week lowered the number of chromosomally normal eggs and increased the chances of miscarriage.

3. Alcohol does not reach the developing embryo until the 3rd week after fertilization, or pregnancy week 4, right after most pregnancy tests turn positive. In other words, even if you got pregnant on your honeymoon while more than a little tipsy and drank cocktails on the beach for the rest of the week, you have nothing to worry about. That alcohol did not reach your embryo.

What about harm to the fetus’s developing brain? Here’s the problem: No one knows at what threshold drinking alcohol becomes harmful, and that threshold may vary from person to person, just like alcohol tolerance and metabolism varies from person to person.

Heavy drinking and frequent binge drinking are clearly bad, but what about that occasional glass of wine or cocktail?

Emily Oster finds the not one drop rule propounded by the CDC and others absurd, and it’s easy to see where she is coming from. Lots of chemicals known to be harmful in large quantities are completely safe in small amounts. As she puts it,

“If you have too many bananas (and I mean a LOT of bananas), the excess of potassium can be a real problem, but no doctor is going around saying “No amount of bananas have been proven safe!” He’d be laughed out of a medical conference.”

But this argument, a version of the Paracelsus principle–the dose makes the poison–depends on the poison in question. Some toxins, like lead, are unsafe at any amount.

We don’t have great information about the actual threshold at which alcohol causes harm, or when harm is most likely to occur. But let’s sift through what we do know.

4. By the third week after conception (the 5th week of pregnancy), alcohol and its byproducts cross the placenta. Based on animal research, the fetus is believed to experience the same blood alcohol level as its mother.

5. Alcohol is a known neurotoxin. Although how alcohol causes damage is not entirely clear, neuronal loss with heavy or binge drinking is evident in animals and in humans. Harmful effects may be especially pronounced in the developing brain, particularly during the first trimester, when many of the changes in facial morphology in FAS appear to originate. Damage to slow growing brain structures, like the cerebellum, likely occurs throughout pregnancy.

6. Large epidemiological studies find no evidence of cognitive impairment with light drinking (1-2 drinks per week) in the second and third trimesters and less than a drink a week, on average, in the first trimester. This research is the basis of Emily Oster’s claim that a drink a day in the second and third trimesters is okay.

One of the largest of these studies is the U.K. Millennium cohort, which has followed a nationally representative sample of 11,000 children born betwen 2000-2002. At age 3, age 5, and age 7, both boys and girls whose mothers drank about 1-2 drinks per week actually had better overall cognitive performance and fewer behavioral and attention problems than children whose mothers abstained from drinking during pregnancy. Heavier drinking, on the other hand, was associated with worse cognitive performance and more behavioral problems.

(The higher test scores among children of light drinkers was almost surely NOT because alcohol benefited their development, but because women who drank lightly were on average more educated and of a higher socioeconomic status than women who abstained. This confounding of light drinking with education and socioeconomic status is actually a huge problem for interpreting this study’s results. Parental education, income, and social class all predict better cognitive performance and fewer behavior problems. So, who is to say that these children would not have been more advantaged had their mothers abstained throughout pregnancy?)

Other studies have found no effect on test scores or mental health at age 11 among children of mothers who drank less than 1 glass per week during their first trimester; no increase in mental health or behavior problems among children of light drinkers at age 2, 5, and 8 (but worse mental health seen among moderate, binge, and heavy drinkers); and no impairment in cognition, learning, or attention among 14 year olds whose mothers drank an average of less than a glass a day early or late in pregnancy; and no reduction in IQ, attention, or executive function at age 5 in women who drank up to an average of 5 drinks per week.

In short, light drinking during pregnancy, less than a drink a day on average, and no more than 1 drink at a sitting, has not been shown to cause detectable harm.

Because light drinking is more common among highly educated, high income women, the advantages of which could mask any subtle impairments caused by small doses of alcohol, we need to take these findings with a grain of salt.

7. Individuals in how quickly they metabolize alcohol and its byproducts. These differences probably influence the threshold at which alcohol causes harm to a fetus. Even among those who drink heavily during pregnancy, only about 5%  will give birth to a baby with Fetal Alcohol Syndrome. 

A recent study looking at IQ at age 8 found similar results for moderate drinkers. Among  slow alcohol metabolizers, moderate drinking (1-6 drinks/week) was linked with lower IQ. No link was found for fast metabolizers, or among poor metabolizers who abstained from alcohol.

The Bottom Line

Drinking more than 2 drinks a week in the first trimester appears to substantially increase the risk of miscarriage. That said, we do not know whether alcohol causes miscarriage. A lack of nausea, or other problems that often go hand in hand with drinking, like smoking, may contribute to this effect.

Alcohol causing miscarriage, however, is biologically plausible. Alcohol can cause chromosomal abnormalities in the egg prior to conception. This does not happen all the time. We all know that alcohol use before conception can lead to perfectly healthy pregnancies. Still, couples who are struggling to conceive may boost their chances by abstaining from alcohol.

What about children’s cognitive abilities and emotional and mental health? Here, very light drinking, less than a drink per week on average, has not been not been shown to be harmful. And many studies find no harmful effects of 1-2 drinks per week.

However, women vary considerably in their ability to metabolize alcohol, based on their body size, liver size, and genetics. Other factors, like whether you drink with food and how quickly you drink (no tequila shots, please!), also affect the amount of alcohol reaching the fetus. These facts make setting a “safe” threshold is impossible.

Given this variability, here’s my personal take: It seems wise to largely avoid alcohol during pregnancy, especially during the first trimester. An occasional glass of wine drunk slowly with dinner is probably fine, but I personally don’t see the upside to pushing the limits.

At the same time, women who drink a glass of wine here and there have no cause for alarm. The CDC’s draconian, not-one-drop stance is probably based on a slippery slope argument. They worry that if they say an occasional glass of wine or beer is fine, women will read their recommendation as license to overindulge.

On the other hand, Emily Oster’s advice to drink “up to 1 drink a day in the second and third trimesters, and 1 to 2 drinks a week in the first trimester” feels too risky for my blood. Most studies define light drinking as 1-2 drinks per week, much lower than Oster’s recommended maximum for the second and third trimesters.

At the end of the day, every woman is going to weigh the risks and benefits of light drinking a little differently. A reasonable woman could see the available evidence and feel comfortable with 1 to 2 drinks a week; another reasonable woman could see the available evidence and decide to abstain entirely.

Curious about drinking after pregnancy? Check out my post on drinking while breastfeeding.

No, C-sections Are Not “Best With a Little Labor”

Children born by C-sections have about 20% higher odds of obesity, asthma, allergies, and Type 1 Diabetes, according several large research reviews.

But are children born by scheduled C-sections especially at risk for health problems, as a recent New York Times piece claims?

“the data showed more health problems among babies born by planned C-section than among those delivered by emergency C-section or vaginal birth, even though the planned surgery is done under more controlled conditions. The finding suggests that the arduous experience of labor — that exhausting, sweaty, utterly unpredictable yet often strangely exhilarating process — may give children a healthy start, even when it’s interrupted by a surgical birth.”

A reader, confused by this New York Times piece, wrote to ask for my take. “Are planned C-sections really less safe?” she asked. “The actual study… didn’t seem to support what the NYTimes article claimed.”

And after reviewing the research myself, I have to agree.

The study in question, led by Dr. Mairead Black of the University of Aberdeen, and one of the largest and best-designed studies on long-term health following delivery by C-section, actually did not find more health problems among children born by planned C-sections than those born by emergency C-sections.

(The sole exception was an unexpected–and probably artifactual–increase in Type 1 Diabetes; more on this in a moment).

How Does This Study Fit in With What We Already Know?

Although C-sections have been consistently linked with poorer long-term health in children, scientists are still not sure why.

One possibility is babies miss out on the “sweaty and exhausting” experience of labor. The physical trauma of birth kickstarts the baby’s internal stress response, pumping cortisol through their veins, and giving their organs, including the lungs, the final push to full maturity.

Another possibility, favored by many scientists, is that C-sections alter the baby’s gut microbiome. C-section  babies miss out on the messy, bacteria-laden, splash into every bodily fluid passage through the birth canal–the route by which nature normally seeds a baby’s gut microbiome.

“If a baby is born naturally, it comes into contact with bacteria from the mother, which might help with immune system development,” lead researcher Dr. Mairead Black told The New York Times.

Compared to babies born by C-section, babies born vaginally have a more diverse and healthy gut microbiome–believed to be critical for their development of a healthy, balanced immune system (one good at attacking pathogens, but not overly jumpy and prone to self-attack).

Or perhaps the issue is not C-section birth per se, but the hodgepodge of pregnancy and birth complications that often result in C-sections, such as stalled labor, intrauterine growth restriction, and preterm birth.

To study one piece of this puzzle, the importance of labor-induced fetal stress, Black and colleagues at the University of Aberdeen in the UK compared babies born by planned versus emergency C-sections. Babies born by planned C-sections experience no labor, while babies born by emergency C-section often experience some, even though it is cut short.

Black and colleagues followed over 300,000 full-term singleton babies born to first-time mothers in Scotland between the years 1993 and 2007. Roughly 4% were born by planned C-sections, and 17% by emergency C-sections.

Compared to children born by emergency C-sections, babies born by emergency C-sections were at no higher risk of virtually every health outcome Black and colleagues assessed–asthma, inflammatory bowel disease, obesity at age 5, cancer, or all-cause mortality. In fact, these children born by planned C-section had a wee bit lower risk of dying during their first year of life.

The one exception: Children born by planned C-section appeared to have 50% higher risk of developing Type 1 Diabetes. (A 50% higher risk sounds scary, but because Type 1 Diabetes is rare, this amounts to only 2 additional diagnoses for every 1000 children.)

As the researchers acknowledge, the apparent increase in Type 1 Diabetes was probably not caused by birth by planned C-section, but by some artifact of their study’s design, a third factor not adequately accounted for in their research.

Why did they think this effect was not real? Because children born by planned C-section were not at higher risk of Type 1 Diabetes compared to children born vaginally, a pattern of results inconsistent with prior research, and one which makes little sense. If anything, the researchers expected the opposite, planned C-sections would lower the risk of Type 1 Diabetes. Earlier research has found severe fetal distress stress during labor–something obviously more common during emergency C-sections than during planned ones–raises the risk of Type 1 Diabetes.

My guess? The researchers were unable to completely account for maternal Type 1 Diabetes. Having a mother with Type 1 boosts a child’s chances of Type 1 Diabetes by about 10-fold. (Black and colleagues did try to control statistically for maternal Type 1 Diabetes, but were missing this information for some of the mothers.) To avoid complications during labor, many women with Type 1 Diabetes deliver by planned C-section.

C-sections Versus Vaginal Births

How did the children born by C-section fare compare to those born vaginally?

Overall, children born by C-section, planned or emergency, were more likely to be hospitalized for asthma and had higher mortality rates during the first year of life as well as throughout childhood.

Contrary to earlier research, though, children born by C-section were no more likely to develop inflammatory bowel disease, Type 1 Diabetes, obesity, or cancer.

The Bottom Line

The NYT headline is misleading: Planned C-sections do not lead to worse health outcomes than emergency ones.

The one exception: children born via planned C-sections had a 50% higher risk of Type 1 Diabetes, but only compared with unplanned C-sections. No difference was seen when comparing children born by planned C-section with those born vaginally, a pattern of results which, as the researchers themselves acknowledge, does not make any sense. In fact, this pattern runs counter to prior research, which suggests severe fetal distress during labor ups the odds of Type 1 Diabetes, and a recent meta-analysis which found that C-sections of all types up the odds of Type 1 Diabetes by about 20%.

Why is birth by C-section associated with poorer health? We still do not know. Given the impossibility of randomized controlled trials for childbirth, we may never know.

But this study does have one take-away: missing out on labor-driven stress response is probably not the critical issue. If it were, we would see significantly worse health outcomes among children of planned C-sections than emergency C-sections.

As for the risks of C-sections overall, that’s too big of a topic for me to tackle here. But I will say this: C-section-driven health risks are minor. They are almost certainly swamped out by who we are–the genetic blessings and curses we bestow on our offspring–and what we do as parents.

(Not reassured? You can always swab your C-section-born baby’s skin and mouth with your vaginal secretions, as widely-respected gut microbiome researcher Rob Knight did after his wife’s emergency C-section. I certainly would.)

 

A Threatened Miscarriage, a Subchorionic Hematoma, and How United Airlines (Nearly) Ate My Baby

Three years ago, sitting with my 15-month-old son and my husband during a long layover, on our way back home from Norway, I felt a sudden gush of warm blood.

So much for my miracle pregnancy, I thought. I was only six weeks along and certain I was miscarrying.

Our return trip was already off to a poor start. United Airlines had cancelled our original flight from Newark home to San Francisco. Then, to rub salt in the wound, they refused to refund our first-class tickets.

We never fly first class, but had made an exception for this trip. We were travelling overseas with my 15-month old son and facing a 9-hour jet lag. The chance of sleeping on route, we decided, was worth the extra cash. We had bought our tickets a year in advance to lower the cost.

But United, being United, told us we would have to request a refund, and then maybe they would grant it. And–perhaps just for kicks–they refused to let us access the first-class lounge while in Newark, because our replacement tickets were now in Economy.

My husband–who nevers argues with anyone behind a counter and hates it when I do–spent half an hour arguing with their “customer service” that they should give us passes to the first class lounge. After all, we had paid for first-class tickets even if we no longer had them. But no dice.

So there we were, exhausted and enraged. I had not slept in over 24 hours. My son, sick for the last 3 days with a high fever, had nursed continuously the entire flight from Oslo to Newark. And then I started bleeding.

At that point, I contemplated tweeting, “United, you ate my baby,” but decided against publicly sharing my pregnancy or what I assumed was an impending miscarriage.

The pregnancy had been a surprise, but a welcome one. We had taken over a year to conceive my son. This time we had not been trying. I was still breastfeeding, and my cycles had only resumed a month earlier. We were planning to wait a few more months and then start trying for #2, expecting that it could easily be another 6 to 12 months before we conceived.

The bleeding tapered off by the next morning. I had no pain or cramping, so little fear of an ectopic pregnancy. And I still felt pregnant: nauseated, tired, and lightheaded.

I called my OB,  but they could not fit me in for another 5 weeks. Until then, they told me, just sit tight. Oh, and assume that I was still pregnant, because a miscarriage would have caused several days of heavy bleeding.

I found another OB.

My new OB ran tests. My HCG levels were normal, but my progesterone was low, perhaps because of the nearly constant breastfeeding, the lack of sleep, and the stress. She could not say for sure. She prescribed progesterone supplements for the rest of my first trimester.

Progesterone helps build up and maintain the uterine lining for implantation of the fertilized egg. High levels of progesterone are required to sustain an early pregnancy. But taking progesterone supplements during the first trimester to prevent a miscarriage is controversial.

Over half of miscarriages result from chromosomal abnormalities, and no amount of progesterone will save these pregnancies. A 2013 review of randomized trials, however, found that while progesterone supplements did not alter the risk of miscarriage for pregnant women as a whole, they did significantly lower the chances of miscarriages for women with 3 or more prior miscarriages.

And for women like me, with a threatened miscarriage (defined as any bleeding within the first 20 weeks of pregnancy), who have more than double the normal odds of a miscarriage*, progesterone supplements appear to cut the risk of miscarriage in half, and oral progesterone, as opposed to suppositories, may be especially effective.

So, although I will never know for sure, my OB may have saved my pregnancy.

A Subchorionic Hematoma

At that initial visit, she also performed an ultrasound. The fetal heartbeat was loud and clear, fast and reassuring, racing along like a rabbit’s. When I heard my baby’s heartbeat, I fully exhaled for the first time in days.

Less reassuringly, the ultrasound revealed a subchorionic hematoma–a blood clot next to the placenta and the cause of my bleeding.

Pregnancies with a subchorionic hematoma are considered high risk. They have a higher risk of miscarriage (17.6% versus 8.9%), stillbirth (1.9% versus 0.9%), and placental abruption (3.6% versus 0.7%). They have a slightly higher risk of preterm delivery (13% versus 10%) and for the waters breaking before labor starts (tv-style labor).

The risk varies by the location of the hematoma. Pregnancies with recurrent bleeding or with hematomas located between the placenta and the uterine wall (retroplacental hematomas) have a higher risk of miscarriage and other pregnancy complications like placenta abruption. Because of the risk of placental abruption, bleeding in the second and third trimesters require immediate medical attention.

As worrisome as these statistics sound, most subchorionic hematomas resolve on their own, as mine eventually did. By 11 weeks, we could no longer see the hematoma on an ultrasound. And thankfully, rest of my pregnancy was uneventful. I gave birth to healthy baby girl, who in a few months will turn 3.

Do you have a story of bleeding in early pregnancy? Was a cause detected, and how did things turn out?

Footnote

*About 20% of women experience bleeding during early pregnancy. Figuring out their chances of a miscarriage is far from simple.

One commonly cited statistic states that roughly 50% of these women eventually miscarry. Some digging reveals that this claim derives from a 1981 obstetrics textbook rather than recent research. (Lots of researchers cite papers that cite papers that cite this textbook, and I am willing to bet that none of them have read the original research behind this claim.)

If bleeding starts after detection of a normal fetal heartbeat, most prospective studies find a much lower rate of miscarriage, of 3.4-5.5%.

References

Haas DM, Ramsey PS. Progestogen for preventing miscarriage. Cochrane Database of Systematic Reviews 2013, Issue 10. Art. No.: CD003511. DOI: 10.1002/14651858.CD003511.pub3.

Nagy S, Bush M, Stone J, Lapinski RH, Gardó S. Clinical significance of subchorionic and retroplacental hematomas detected in the first trimester of pregnancy. Obstet Gynecol. 2003 Jul;102(1):94-100.

Sotiriadis A, Papatheodorou S, Makrydimas G. Threatened miscarriage: evaluation and management. BMJ : British Medical Journal. 2004;329(7458):152-155.

Trop I, Levine D. Hemorrhage during pregnancy: sonography and MR imaging. AJR Am J Roentgenol. 2001 Mar;176(3):607-15.

Tuuli MG, Norman SM, Odibo AO, Macones GA, Cahill AG. Perinatal outcomes in women with subchorionic hematoma: a systematic review and meta-analysis. Obstet Gynecol. 2011 May;117(5):1205-12. doi: 10.1097/AOG.0b013e31821568de.

Folic Acid During Early Pregnancy May Lower the Risk of Autism

We all know that taking folic acid before and during early pregnancy helps prevent neural tube defects like spina bifida and anencephaly. But I for one was surprised to learn that taking folic acid may also help prevent autism.

Continue reading Folic Acid During Early Pregnancy May Lower the Risk of Autism

No More Milestone Talk For Me

Stand at our neighborhood playground for a few minutes and you are almost sure to hear remarks like these:

“My child started walking at 8 months.”

“My two-year-old is speaking in full sentences.”

“My son was potty trained at 18 months.”

Some of these remarks have been made to me. And some, I am ashamed to admit, have been made by me. But no longer. I refuse to take part in these conversations any longer.

Why? Because they always make someone feel bad. Someone’s child always ends up on the downside of the comparison.

And that sucks.

Of course, intellectually we all know that our children are not going to be the best at everything. And for a while, I was mentally stuck there: Why was I letting these kinds of conversations make me feel bad? Surely, I know my kids were wonderful. Surely, I love them for who they are and not for what they accomplish.

But, then, I realized I was asking the wrong question.

Here’s the right question: Does talking about our children’s accomplishments lend itself to good conversation?

Continue reading No More Milestone Talk For Me

Back Sleeping During Pregnancy and the Sydney Stillbirth Study

Pregnancy can be cruel. Just when you are at your most swollen, bloated, and exhausted, sleep proves frustratingly elusive. Every night, you toss and turn, trying to find a comfortable position, your back aching, and your belly pressing down on your bladder. And then, as you finally start to drift off, you realize you need to pee.

To make matters worse, despite having an enormous bowling ball attached to your stomach, you are told you cannot sleep on your back:

“After 16 weeks of pregnancy, experts advise women to not sleep on their backs, but rather should lie on their sides, ideally the left side.” – mamalette

Who came up with this idea?

This advice stems three studies that have linked back sleeping with late stillbirth (pregnancy loss after 28 weeks). (Interestingly these warnings predated the three studies, so they are not exactly the reason women are told to avoid back sleeping)

I described the first two studies, one conducted in Ghana, the other in New Zealand, in an earlier post, and concluded that not only did they provide no reason for alarm, they certainly do not justify blanket advice again back sleeping.

In 2015, a third study came out linking back sleeping with late stillbirth. Does it change the overall picture?

Continue reading Back Sleeping During Pregnancy and the Sydney Stillbirth Study

Don’t Count on Breastfeeding to Help You Shed Your Baby Weight

Breastfeeding melts off the baby weight, right? Breastfeeding leads to an “earlier return to prepregnancy weight,” according to the American Academy of Pediatrics (AAP).

This is because “breastfeeding burns extra calories, so it can help you lose pregnancy weight faster,” as many popular websites, like WebMd claim.

Sounds pretty clear cut, right?

So when I failed to lose weight while breastfeeding my first child, I was shocked. Weren’t those pregnancy pounds supposed to be falling off? Why were my pre-pregnancy jeans still collecting dust in the back of my closet?

Breastfeeding an infant does burn an average of 480 calories a day. So why wasn’t I losing more weight?

But like so many other alleged benefits of breastfeeding, breastfeeding-aided weight loss turns out to be vastly overblown.

In other words, my experience was completely normal. For most well-nourished women, long-term breastfeeding results in only a trivial amount of extra weight loss by 6 months postpartum, usually only of 1-2 lbs.

Continue reading Don’t Count on Breastfeeding to Help You Shed Your Baby Weight

Questioning Breastfeeding’s Benefits Does Not Make Me Anti-Breastfeeding

Earlier this week, I wrote about the alleged benefits of breastfeeding being vastly overstated.

My goal in writing that post was not to nurse some long-standing grudge against breastfeeding advocates. Nor was it an attempt to justify my own parenting choices: I breastfed both my children for well over a year.

(And yes, as some readers have inquired, I know just how wonderful breastfeeding can be. How breastfeeding your baby can be calming and joyful, even magical. But whether I found breastfeeding magical or a chore–or, in actuality, both–has nothing to do with whether it lowers the risk of asthma, or heart disease, or anything else.)

In response to my post, someone shared this comment on Facebook:

“Anyone who thinks this [my post] a solid piece of work needs to read my latest book, Milk Matters: infant feeding and immune disorder. No one has to prove that breastfeeding (the evolutionary and physiological norm that provides free stem cell transplants) makes a positive difference. Those who assume, claim or promote artificial feeding as safe or adequate need to prove that deviating from such basic physiological norms is safe, that there are no short or long term harms from doing so. …”

I am sharing this comment not because I find it particularly compelling, but because I think it nicely illustrates the problem with arguments made by many breastfeeding advocates: They start with the assumption that breast is best. And then, inevitably, they fail to scrutinize the evidence, no matter how flimsy, that supports that assumption.

And the evidence is flimsy indeed. Most of the alleged benefits of breastfeeding are found only in observational studies, which are widely acknowledged as biased. On average, breastfeeding mothers have a higher levels of education, higher incomes, and live in safer neighborhoods than formula-feeding mothers, granting their children an early leg up in life. Separating the effects of breastfeeding from these other advantages is next to impossible.

How do we know that these observational studies are biased? Primarily because we do not find the same benefits in better-designed studies–sibling comparison studies and the PROBIT randomized controlled trial. The only clear-cut benefit seen in these studies is a lower risk of severe vomiting and diarrhea during infancy. (For a detailed summary, see my earlier post).

To be fair, breastfeeding advocates are right, in a way. Breastmilk does contains numerous hormonal, antimicrobial, immunological, and nutritional factors not found in formula. This is why breastmilk helps protect against vomiting and diarrhea during infancy.

Before the advent of clean water, sanitation, and modern medicine, breastfeeding was frequently life-saving. In countries where access to these resources remains limited, it still is. There’s no bigger possible benefit than survival.

But these beneficial properties do not imply that breastmilk has any long-term benefits for the panoply of modern ailments: allergies, asthma, obesity, type 2 diabetes, and cardiovascular disease. We cannot claim such long-term benefits without sound empirical evidence. And that is entirely lacking.

If the American Academy of Pediatrics, and others were to say, “We recommend breastfeeding because it reduces the risk of severe diarrhea and vomiting during infancy, and because breastmilk contains unique immune, hormonal, and nutritional factors not found in formula, the long-term benefits of which are unknown,” I would have no problem with their claims.

But instead, they have chosen to present poor quality evidence as fact. Playing fast and loose with the evidence in this way undermines their credibility. Worse, it violates the trust that women have placed in them.

Breastfeeding Benefits: The Real, the Imagined, and the Exaggerated

A good friend of mine living in Scotland, who had a baby last year, mentioned to me how disappointed he has been with the U.K. National Health Service’s promotion of breastfeeding. Calling the alleged benefits overstated, he said, is itself an understatement.

I nodded in general agreement, acknowledging that many of the alleged benefits of breastfeeding have only been found in observational studies. 

Observational studies on breastfeeding merit skepticism, because they all suffer from the same major problem: breastfed infants on average differ from formula-fed infants not just in how they are fed in infancy, but in practically every other possible way–maternal education, maternal IQ, poverty, neighborhood safety, exposure to environmental toxins, race, and type and quality of childcare. In scientific terms, breastfeeding is confounded, out the wazoo.

We cannot tell which benefits found in an observational study derive from breastfeeding rather than from the myriad other advantages linked with breastfeeding.

(The “good” observational studies attempt to control statistically for the other relative advantages of breastfed infants. Unfortunately, controlling for confounds only works well when (1) all the important potential confounds are known, and (2) when there is a fair amount of overlap between the groups being compared. Neither of which is true when it comes to breastfeeding.)

In an ideal world, we would settle this question by conducting several large randomized controlled trials (RCTs), in which new mothers would be randomly assigned to breastfeed. RCTs are the gold standard in medicine for determining whether a true cause and effect relationship exists. In practice, though, such trials are neither feasible nor ethical.

Fortunately, we have the next best thing: a handful of studies that have cleverly circumvented the problem of confounding. These fall into two categories:

  • sibling studies, which compare siblings from the same families who were breastfed for different lengths of time, or who were not both breastfed.
  • a large RCT of a highly successful breastfeeding intervention (PROBIT Trial).

(Is the PROBIT Trial an exception to the no-RCT rule? No. Women in the PROBIT trial were not randomly assigned to breastfed or not; they were randomly assigned to receive a breastfeeding intervention or not.)

After my friend and I spoke about his irritation with the medical organizations like the American Academy of Pediatrics (AAP) and NHS overstating the benefits of breastfeeding, I was dissatisfied with my vague sense that he was right. I wanted to know exactly which benefits had been oversold and exactly which were supported not just by observational studies but by better-designed studies.

The short answer: Nearly all the alleged long-term benefits are likely the result of confounding, not breastfeeding. Better-designed studies find only a handful of real benefits: a reduced chance of severe gastrointestinal infections and a lower risk of eczema during infancy, and perhaps a small boost in childhood IQ.

Alleged Breastfeeding Benefits According to the NHS

According to the NHS, breastfed infants are…

  • less likely to suffer from vomiting or diarrhea and therefore less likely to go to hospital
  • less likely to develop type 2 diabetes in later life
  • less likely to become obese in later life
  • less likely to suffer from heart disease in later life
  • less likely to suffer from constipation
  • less likely to get a chest or ear infection and therefore less likely to go to hospital
  • less likely to suffer from tooth development problems
  • more likely to have good communication and speech skills
  • more likely to have good circulation
  • less likely to suffer from wind, colic and constipation
  • less likely to develop eczema or asthma

Sounds pretty impressive, right? Until you set aside the evidence from observational studies…

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Continue reading Breastfeeding Benefits: The Real, the Imagined, and the Exaggerated

Blood-Based Tests of Fetal Sex: Are They Accurate?

Many expectant parents are impatient to learn if they are having a boy or a girl. So they may be attracted to new companies, like SneakPeek, which claim to be able to determine your baby’s sex with 99% accuracy early in the first trimester, with only a simple blood draw.

These new tests rely on what is known as cell free fetal DNA (cffDNA)–small fragments of DNA shed from the placenta into your bloodstream.

Unfortunately, according to a 2011 meta-analysis published in JAMA, some of these companies overstate the accuracy of their tests. The meta-analysis found that none of these cfDNA-based tests are accurate before 7 weeks. (The meta-analysis also examined urine-based tests. None of these were accurate.)

Between 7 and 20 weeks, accuracy for these blood-based tests ranged from 95-98%, depending on the specific techniques employed and the baby’s actual sex. (The tests were more accurate when they use a DNA amplification technique known as real-time quantitative polymerase chain reaction.) Only after 20 weeks were the blood-based tests 97-99% accurate.

Continue reading Blood-Based Tests of Fetal Sex: Are They Accurate?