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
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.

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Author: Amy Kiefer

I am a research scientist and mother of three munchkins. I live in the Bay Area and when I am not child wrangling and catching up on lost sleep, I love digging into the research on all things fertility, pregnancy, and breastfeeding related.

20 thoughts on “Morning Sickness & Miscarriage: How Much Does Nausea Lower Your Risk?”

  1. Thanks Amy for this post. Somehow, I find it comforting to read some real scientific facts about so-called “morning sickness”, even though the main conclusion is that scientists don’t understand why it’s there and don’t know how to make it stop. In my experience NVP per se is bad, but what makes it even worse is the lack of consideration you get from healthcare providers and the society. From “It’s all in your head” to “You’re so lucky to be pregnant, why are you complaining?” and “You can’t get any medicine but you should try homeopathy”, most reactions I got to my severe NVP during my first pregnancy didn’t help much… I’m now 3 months into my second pregnancy and, surprisingly enough, NVP is less severe now than it was the first time (and no, it’s not a sign of impending miscarriage, we’ve just had a ultrasound, everything’s fine). I’d love to understand why it is so, from a scientific perspective: how can hormon releases be so different from one pregnancy to the next? Do you have any readings to suggest? Thanks!!

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    1. Hi Clara!

      I agree–unsympathetic reactions to morning sickness are infuriating. Even recently, some doctors have subscribed to the idea that psychological problems lead to hyperemesis gravidarum, an incredibly condescending and retrogressive view. I have no doubt that women would receive more empathy and better treatments if men suffered from morning sickness too.

      As for why you’d have less morning sickness the second time around, I don’t think there are any truly good answers. Some things that might be at play: Older women tend to have less severe morning sickness. Women who have very severe morning sickness, with a diagnosis of hyperemesis gravidarum (HG), are more likely to be carrying girls (about 60% of the time). Oddly enough, fetal sex does not correspond to severity of NVP symptoms for women without HG.

      You may want to read some of Marlena Schoenberg Fejzo’s publications. She’s a researcher who studies the genetics of HG, and she suffered from extremely severe HG during her second pregnancy. If you needed rehydration for severe morning sickness during your first pregnancy, you might also be eligible for her ongoing study on the severity of morning sickness.

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      1. Thanks Amy for your reply! I was lucky enough to escape HG on my first pregnancy. And even luckier this time: now in my second trimester, nausea almost disappeared, what a relief 🙂

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  2. I’ve had 5 miscarriages, and was sick as a dog with all of them. In my case, at least, morning sickness did not equal healthy pregnancy. 😦

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    1. I am so sorry to hear about your miscarriages. And you provide a good reminder–none of these associations are 100%. Some people with morning sickness will go on to miscarry, and some without will go on to have perfect normal healthy pregnancies.

      Have you talked with someone who specializes in recurrent losses about what might be going on?

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  3. It might be reassuring and comforting for pregnant women who have MS. However, for pregnant women with no or very little nausea like me, reading everywhere that MS is a sign of an healthy pregnancy is very stressing.. I am spending my whole first trimester worrying. I am almost 11 weeks and hope everything is going well and cannot wait to pass the 14-week mark.

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    1. I can see how not experiencing nausea might be scary too. At 11 weeks, though, your chances of a miscarriage are much lower than earlier, so it’s very likely you just lucked out when it came to morning sickness.

      Congrats on your pregnancy–and I hope everything continues to go smoothly.

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  4. Hi, I’m not sure I understand your odds comparison, would you be able to explain a bit more? The y axis scale of your graph – odds of miscarrying – is ‘odds’ a measurement? I’m not sure I understand the unit being measured. So in other words – a 0.1 chance of miscarrying, the highest one in the graph, does that mean a 1 in 9 chance? Or is this way too simplistic. This may be my lack of stats knowledge showing Thanks!

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  5. Might sound like silly questions but what if your man is experiencing “morning sickness” too? I read your miscarriage pages and data. Is there any data for when he gets sick with you or is it an entirely different subject that has no grounding on miscarriage statistics?

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  6. Hi. Thanks for your post–I like your stuff. I’m a researcher (epigenetics) and acupuncturist, and I just wanted to push back a bit on your statement that “acupuncture, though popular, does not appear to be effective.” I know this to be untrue personally and clinically, and I do not want folks who are suffering and read this to dismiss what is a gentle, non-pharmaceutical and effective solution.

    Now don’t get me wrong–acupuncture does not *cure* NVP. Acupuncture doesn’t work against nature and I am one of those scientists who believes that we are sick during pregnancy because this sickness played a role evolutionarily, ie, those who got sick were less likely to eat toxic foods and thus fitter than others. But I have never met a pregnant woman with NVP (and I have treated dozens of them) who did not get relief from acupuncture, either for a day, and sometimes up to five days.

    Ironically, I don’t know the research on this. You probably do, though I thought it was interesting that your dismissal of acupuncture was without evidence. I’m sure there are articles that say acupuncture doesn’t work for NVP because there is tons of sloppy research on acupuncture by non-practitioners. This isn’t a bias of mine, truly, but I am qualified to make that statement as a scientist and practitioner.

    I will tell you, when I am treating something tricky I live and breathe the evidence–all I do is read paper after paper. Parkinson’s, neuralgia, this is some tricky stuff to treat. There are lots of opinions. Reading the data matters. But with NVP, I haven’t even done a single search. There’s no need to. It’s the most simple treatment there is. Depending on severity it can be done in 5 minutes with 4 needles. And it works.

    You don’t seem to be someone who would make a comment like the aforementioned without evidence, so even though you didn’t cite it, I trust that you made an informed comment and were not providing readers with your opinion. But please, this is my plea to women who need help with NVP and who are reading your blog (and thus interested in evidence): regardless of what researcher says acupuncture doesn’t work for NVP, talk to people. Or better yet, try it yourself. Research does not and cannot (and I am a researcher here) fully capture the lived experience. Be open to helping yourself naturally.

    Two stories for those who want some anecdotal data:

    (1) I treated a woman, pregnant with twins, with the most severe NVP I’ve ever seen. She hadn’t tried acupuncture before pregnancy so didn’t think of it for her NVP. She found me at 9 weeks, at which time she had lost significant weight. I treated her twice a week until 14 weeks. On treatment days, she feels like normal–she eats whatever she wants, doesn’t vomit, and doesn’t have a problem. On the day after treatment she starts to feel mildly nauseated, but can still eat normally and doesn’t vomit. Two days after treatment she is very nauseated. She would come back the 3-4 days after treatment. By the way, she drove 75 minutes to come for treatment. After getting treated she gained her weight back and continued to gain.

    (2) I treat myself! I am pregnant (that’s how I got to this site!) and suffer from NVP. When I start to feel sick, I treat myself. I do mini treatments (I take care of a 2 year old), so not as effective as real treatments, but my pattern is I treat so I can eat. Treat myself, eat, treat myself again when I can’t eat the next time. I wouldn’t take the time during the day to stick myself with needles if it didn’t provide me with significant relief, believe me.

    So acupuncture does work for NVP. It doesn’t rid your first trimester of the experience, but it makes life much happier. This is less an advertisement for acupuncture and more a counter-balance to the comment that acupuncture isn’t effective.

    Thanks.

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    1. I too thought that last sentence regarding acupuncture was very brief and decisive sounding for something I found DOES work personally. I was reading this because I am pregnant with my 3rd, am 6 weeks along and not feeling sick yet as I did with my first two and feeling anxious about it because he grass is always greener on the other side. It is reassuring when you can’t feel movement yet or listen for a heartbeat to feel some symptom that your baby is well, even if it is miserable. With my second I started seeing am accupumcturist around 8 weeks after feeling sick for 2 and being sick of it! In my first pregnancy I was sick until 10.5 weeks. With my second after starting acupuncture I was much more mildly ill and then completely better at 10 weeks.

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  7. Excellent summary! Might be worth including that Diclegis is actually a combination of two otherwise OTC medications (doxylamine AKA Unisom and B6) and that its effect size in studies has been very small… more serious options for nausea control include ondansetron AKA Zofran.

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  8. i am 5 days away to the 2nd trimester and i have not had any morning sickness …though i have all the other symptoms and bump already showing . i can also feel my baby move . was wondering if am among the lucky ones

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  9. I had a miscarriage in early December last year at about 12 weeks. I had had no morning sickness. I’m now five weeks pregnant and I’m increasingly anxious and paranoid as so far no sickness this time either. I think I’m feeling slightly nauseous from time to time but not sure if it’s my mind playing tricks on me. I’m going to sleep each night hoping I’ll wake up sick the next day.

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