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

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

About 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 comes with one one big silver lining: Nausea often signals a healthy pregnancy. As you probably know, women with nausea have a much lower risk of miscarrying and–as is less widely known–a lower chance of preterm labor.

For miscarriage, the 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
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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.

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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.

Fertility in Your 30s and 40s: 7 Things You Need to Know

Getting pregnant is a numbers game. Here’s what every woman should know about her odds of success in her late 30s and early 40s.

One of my former colleagues became pregnant her first shot out of the barn, the first month off the pill. Her story would hardly be noteworthy, except that she was 41 at the time.

She wanted to tell other women about her experience, she confided to me. She saw it as a sign that women can have children after age 40.

I simply nodded in response, while I privately wondered if she had not just been very lucky.

But–and this is key–how lucky?

Having a baby in your 30s and early 40s–and earlier, for that matter–is always a chance event. There will be outliers. Some women will give birth naturally at 44. Some women will suffer from early menopause at age 30. But outliers tells us little about the norm.

Anyone who wants to play the conception game, especially if they are postponing childbearing, needs to put anecdotes aside and try to grasp the actual odds. Here’s what every woman needs to know:

Continue reading “Fertility in Your 30s and 40s: 7 Things You Need to Know”