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Posts by Amy Kiefer

Learn everything you ever wanted to know about prenatal genetic testing by downloading my ebook!

Who needs prenatal testing for genetic disorders? How much does your risk of carrying a baby with a genetic disorder increase with your age? Which prenatal test or screen is right for you?

These are among the questions my amazing co-author Molly Dickens (and fellow pregnant scientist blogger/partner-in-crime) and I tackle in our new ebook on prenatal testing. We provide a quick “cheat sheet” on how these tests compare, and then dig into the nitty-gritty details of each as well as the history of prenatal testing and how to estimate your personal risk of carrying a baby with a genetic disorder.

Even having gone through prenatal testing twice before, I was still surprised to learn while researching this book that…

  1. Testing only women over 35, as was the case in the 80s and early 90s, misses around 70% of the cases of Down’s Syndrome.
  2. The risk of miscarriage from amnio and CVS is around 1 in 1000–far, far lower than the still commonly cited but outdated 1 in 100 estimate.
  3. Until you are 38 years old, you are more likely to carry a baby with a chromosomal disorders involving tiny pieces of chromosomes than carry a baby with disorder involving missing or extra whole chromosomes–but these disorders are not well detected by any prenatal screens. This is a huge problem, because younger women are often advised to get screens over diagnostic testing.
  4. How women under 35 are more than twice as likely to get a false alarms on prenatal screens as women over 35.

And so much more that I am excited to share.

We all need to up-to-date, evidence-based information to make the best decisions for us and our families. But with prenatal testing rapidly evolving, sometimes doctors and other healthcare professionals are woefully behind or outright misinformed on the latest developments. So please download and share with fellow parents-to-be!

Download the pdf here: Prenatal Testing ebook.

How much iron does my baby need?

Too little iron in infancy can cause irreversible cognitive deficits. And iron deficiency can have no symptoms. It’s scary.

Yet the advice parents get on meeting your baby’s iron needs is complex, conflicting, and incredibly confusing.

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Breast may be best, but why isn’t it better?

In honor of World Breastfeeding Week (yes, yes, I know–it ended yesterday), we need to talk about a widely overlooked aspect of breastfeeding, its recipients!

Nope, I am not talking about our babies. (After all, who could overlook them?) I am talking about their gut bacteria.

Breast milk contains special carbohydrates (called HMOs for Human Milk Oligosaccharides) designed to nourish specific gut bacteria, especially a type known as Bifidobacteria. Bifidobacteria contain genes desiged to metabolize HMOs–implying they have co-evolved with us for a long time.

This process of seeding your baby’s gut begins not with breastfeeding, though, but before birth. During pregnancy, women’s bodies cultivate these bacteria while pruning out others, seemingly in preparation to pass them onto our babies during birth.

Why does this matter? Health benefits.

Breastfeeding may benefit health indirectly–by cultivating the right gut bacteria. Scientists now believe that having the right balance of gut bacteria helps to calibrate your baby’s immune system and metabolism, possibly with lifelong effects.

I dig into the latest research on this breastfeeding-gut-health axis in my latest post for BloomLife. Check it out!

https://preg-u.bloomlife.com/breast-may-be-best-but-why-isn…

Drinking While Nursing: 7 Things to Know

While over half of mothers in the U.S. drink alcohol while breastfeeding, many of us are foggy on how this does (or does not) affect our babies.

Can you drink a glass of wine while breastfeeding your baby? Or do you need you wait 2-3 hours for the alcohol to clear? And exactly how much alcohol is too much alcohol to nurse?

Doctors and trusted sources like KellyMom and Babycenter give wildly conflicting advice on these points.

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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!

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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.

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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.

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

For most women, the first trimester is undeniably rough. After briefly honeymoon of revelling in being pregnant (two lines!), you start to feel sick as a dog, all day long.

At least, most of us do. An estimated 70-80% of pregnant women experience nausea during their first trimester, and about 50% also experience vomiting.

Not that it will make you feel any better, morning sickness does imply one big silver lining: Nausea often 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.

For miscarriage, your risk is not just a tiny bit lower, but a huge whopping amount lower. Women with nausea have roughly a third of the risk of women without symptoms. Women over 35 with nausea, who because of their age have a higher risk of miscarriage, have only about a fifth of the odds of a miscarriage as those without nausea.

These are sizeable effects. Still, a lack of morning sickness does not necessarily signal an impending miscarriage. A lucky 20-30% of pregnant women never experience any morning sickness but give birth to perfectly healthy babies.

Luck is not the only factor. The more babies you have had, the worse your nausea tends to be in subsequent pregnancies, and the more likely it is to last well into your 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.

And finally, timing matters: Before 7 weeks, a lack of nausea does not predict miscarriage risk.

A Quick Note on Terminology

Although commonly called “morning sickness”, most medical professionals prefer the term nausea and vomiting of the pregnancy (NVP), because symptoms typically occur all day long, not just in the morning, as many first-time mums-to-be discover to their dismay. In fact, in one study, less than 2% of women with “morning sickness” had nausea and vomiting only in the morning. Others 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 90% women who will experience any morning sickness, though, that all day queasy, on-a-winding-road-with-a-bad-hangover feeling starts by your 9th week of pregnancy, or 7 weeks after conception.

It’s only then, in the 8th 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.

Adapted from

Adapted from

Whether symptoms start early or late did not seem to matter, provided nausea began by the 8th week. And once the first trimester was over, nausea no longer had bearing on the chances of a loss.

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

NVP is one of pregnancy’s great mysteries. No one knows why it occurs. No one knows what, at a biological levels, causes NVP. No one knows whether NVP serves a purpose, as some evolutionary theorists have proposed, or whether it is just an unpleasant side effect of hormonal shifts during early pregnancy.

In terms of its biological underpinnings, rapid rises in hormones like estrogen, progesterone, and human chorionic gonadotropin (HCG)–a hormone produced by the embryo upon implantation and used to detect pregnancy–are often fingered as potential culprits, but the evidence for their role is only circumstantial.

HCG, the hormone with the most evidence for a role in NVP, rises exponentially during the early weeks of pregnancy and reached peak concentration between 8-10 weeks of pregnancy. This rise, perhaps not coincidentally, coincides with when NVP symptoms are usually at their worst. Conditions which cause high HCG levels like Down’s Syndrome, molar pregnancies, and twin pregnancies often cause particularly severe NVP. Still, HCG levels do not reliably distinguish women with and without NVP, and no one understands why, at a biological level, HCG would induce nausea.

Pregnancy often comes with a bloodhound-like ability to detect odors. This heightened sense of smell likely also contributes to NVP. 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 70-80%.

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.

So nausea and vomiting are good. But they are also bad. I mean, they really suck.

Let’s be clear: nausea and vomiting are more than a simple inconvenience. Just for starters, 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.

And 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, seek help. Early treatment may help prevent NVP from becoming dangerously severe.

What Can You Do?

Women with NVP are advised to eat small, frequent meals of bland low fat foods like dry toast, bananas, and rice, to eat before getting out of bed in the morning, and to avoid strong odors (as if that were possible during early pregnancy!).

If these efforts fail to bring relief, an FDA-approved treatment is now available, for the first time in 30 years. (Many women take Zofran off label, but the FDA has never approved Zofran for use during pregnancy.)

In 2013, the FDA approved Diclegis (a delayed release combination of vitamin B6 and doxylamine, the active ingredient in Unisom) as pregnancy category A, meaning it is safe for use during pregnancy, including in the first trimester.

Diclegis is not a new drug, but an old one, pulled from the U.S. market in 1983 because its manufacturer could not afford to defend itself against what we now know to be groundless lawsuits alleging the drug caused birth defects. At its height, around 25% of pregnant women took it for NVP.

If you prefer natural therapies, some limited evidence suggests that ginger and vitamin B6 help alleviate nausea. Acupuncture, although popular, does not appear to be effective.

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 in particular seem to worsen the effects of alcohol; alcohol lowers the amount of nourishment reaching 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 considered 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. Individual differences in alcohol metabolism and clearance probably determine the threshold at which alcohol causes harm. This is clear even among heavy drinkers: Only about 5% of babies born to women who abuse alcohol during pregnancy suffer from FAS.

But a recent study looking at IQ at age 8 found that among women who were genetically poor alcohol metabolizers, moderate drinking (1-6 drinks/week) was associated with lower IQ. Children of fast alcohol metabolizers, on the other hand, did not have lower IQs on average, nor did children of among poor metabolizers who abstained from drinking during pregnancy.

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 along with alcohol, like smoking, may contribute to or fully explain this effect.

One possible reason is that alcohol can cause chromosomal abnormalities in the egg prior to conception. Alcohol use before conception does NOT preclude a healthy pregnancy (clearly!). 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. So setting a “safe” threshold is basically 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 drank 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. If they say an occasional glass of wine or beer is fine, then some women might read this 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.

Naturally, 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.

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

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