What Causes Morning Sickness

Laury asks: What causes morning sickness?

vomit-womanMost mothers will tell you that “morning sickness” is a misnomer, and that it should really be called “all day sickness.” In fact, it’s sometimes called “nausea and vomiting during pregnancy” or NVP. Pregnant women have been experiencing this unfortunate side effect of growing a parasite… err human inside them seemingly for as long as there have been humans… or at least humans who wrote stuff down. But unfortunately doctors aren’t yet 100% sure what’s causing the issue.

That said, they do have some pretty plausible theories. The most widely accepted of these is that morning sickness is a result of the creation of the human chorionic gonadotrophin hormone (hCG), which is produced only during pregnancy. (That’s the hormone those at-home pregnancy tests detect to give you a positive or negative result.) It’s thought that because the body is unused to this hormone, the sudden rapid rise of it results in the nausea and vomiting that so many women suffer from in the early stages of pregnancy.

Morning sickness usually starts around the 4th week of pregnancy, and a majority of women find that it fades away towards the end of the first trimester. However, about 1/5 of women experience morning sickness well into the second trimester, and some are sick until their babies are born.

The 4th week of pregnancy is right around the time that a pregnancy test will turn up positive. Before then, the level of hCG in the system is often too low to be picked up by at-home tests (though a blood test at the doctor’s office may pick it up earlier). Generally, the level of hCG in the system will double every 72 hours in the first 12 weeks of pregnancy, when it reaches its peak. After that, the hCG tapers off.

Considering most women find that morning sickness abates after the first trimester, the hCG theory is a pretty good one. However, there are several other theories we’d be remiss if we didn’t mention, though these aren’t all created equal, just theories that have been highly touted over the years with varying levels of research backing them up (or not in some cases):

  • An increase in progesterone and estrogen during pregnancy causes the uterine muscles to relax, but it also might cause the stomach and intestines to relax, leading to a build-up of stomach acid.
  • One of the most long touted, and somewhat controversial, is that morning sickness is a way of ridding the body of toxins that are harmful to the vulnerable fetus in the early stages. Bland foods typically have fewer “toxins,” which is why it’s easier to keep them down, or so the theory goes. One woman, Margie Profet, theorized that women who ate vegetables were at higher risk for morning sickness because there were toxins in vegetables that weren’t harmful to adults, but were harmful to weeks-old fetuses. However, this has been largely disproven by various studies and eating plenty of fruits and vegetables has been shown to be extremely good for your little parasite.
  • A change in blood pressure—specifically, lower blood pressure. During pregnancy, circulation expands and hormonal changes can cause blood vessels to dilate. Because of this, many women experience lower blood pressure, which can lead to faintness and dizziness. If this doesn’t cause the nausea, it can certainly exacerbate the problem.
  • The heightened sense of smell that comes along with pregnancy can reveal odours that can turn the stomach.
  • Hypoglycemia, or low blood sugar, caused by the lovable baby/parasite sucking away all of the mother’s nutrients, though this theory isn’t backed up by much evidence.

Of course, what many mothers really want to know isn’t as much why it happens, but how to prevent morning sickness from happening. Due to the mysterious nature of morning sickness, there’s no hard and fast cure, but many women have found some relief using common remedies for nausea and vomiting, plus a few other tricks. (Of course, if you are pregnant you should always consult a doctor before taking advice found on the internet, even in the well researched parts like this site- some of the below is simply based on anecdotal evidence, which… let’s just say we humans are really bad at determining what’s actually going on that way… ;-)):

  • Avoid having an empty stomach. Eat small meals throughout the day so that you’re never running on empty. Many women say eating a few dry crackers before you get out of bed in the morning works wonders. (Whole grain Goldfish crackers also reportedly work well and are a tad tastier than plain dry crackers.)  Carrying around a bag of these crackers or gold fish and occasionally snacking on them throughout the day can also help keep the edge off.
  • Anecdotally many women claim that eating a banana before going to sleep helps with nausea in the morning.
  • Avoid sugary (or rather non-fruit type sugary), spicy, and fried foods.
  • Take a ginger supplement or drink ginger tea. Ginger calms the stomach and should help with nausea. (Though be careful with this one, you can easily get too much Ginger which is thought to be harmful, particularly in the first trimester when morning sickness is rearing its ugly head.)
  • Take your pre-natal vitamins and other supplements at night or the evening rather than in the morning. They can irritate your stomach, which you might not notice so much while you’re asleep.
  • Take vitamin B6, which has been shown to improve symptoms of morning sickness. This method is highly recommended by the American College of Obstetricians and Gynecologists.

Of course, sometimes it’s best just to avoid things that trigger your nausea, if you can identify them. If you notice a certain smell or certain food is causing the problem, stay away from it. (Hey—it’s as good of an excuse as any to make someone else take out the trash for you for the next few weeks!)

The good news is that normal morning sickness doesn’t usually have much of an effect on the developing baby, and it shouldn’t be harmed by its host vomiting into the toilet a few times a day. The growing little parasite will pretty much take what it needs from you either way.  It only becomes risky if the mother can’t keep any food or liquids down at all for several days, at which point the mother should contact a doctor.

If you liked this article, you might also enjoy our new popular podcast, The BrainFood Show (iTunes, Spotify, Google Play Music, Feed), as well as:

Bonus Fact:

  • There are also some severe cases of morning sickness. One of these is hyperemesis gravidarum, which was in the news a while ago in the early stages of Duchess Kate’s pregnancy with Prince George. In her case, it required medical intervention (and resulted in announcing the pregnancy a lot earlier than she would have liked). Women around the world can take solace in the fact that, if they’re suffering, at least royalty is suffering with them.
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  • Hi Emily; Nice article,very informative. However, your use of the term “parasite” wasn’t really very funny. I hope you were trying to be funny…?

    • Daven Hiskey

      @F.Barsook: According to Oxford, parasite: “an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host’s expense.” But ya, it is a joke, except growing babies in the womb do fit the definition exactly. 🙂

      • By that definition all humans are parasites. Using this term for a baby is patently offensive and shows poor judgment by the author.

  • I found it funny, and I’m a mom of 3. So maybe y’all should relaaaax 🙂