What Causes Morning Sickness? 10 of the Most Plausible Theories

Find out what causes morning sickness — one of the most common pregnancy symptoms. Plus, learn how knowing this information can help you feel better faster.

Find out what causes morning sickness — one of the most common pregnancy symptoms. Plus, learn how knowing this information can help you feel better faster.

Morning sickness certainly isn’t fun. Along with heartburn, pregnancy acne, and constipation, it can be just one of the strange but common things that happen during pregnancy. But what exactly causes morning sickness? Why do so many of us feel so yucky during those first few months of pregnancy?

What Causes Morning Sickness?

No one knows for sure what causes morning sickness, but there are some compelling theories out there. And it’s important to understand the root causes of morning sickness, because it can influence which natural remedies work best for you.

1. Hormones from pregnancies

The most widely accepted explanation for what causes morning sickness is that it’s hormonal. The hormone hCG rises rapidly in the beginning of pregnancy, which is often blamed for making women feel queasy and sick. No one knows why, but hCG is a suspect because the peak of hCG coincides with the peak of morning sickness (the end of the first trimester).

2. Weak liver

Many women have found that pre-pregnancy and during-pregnancy liver support made a huge difference in the severity of their morning sickness—or eliminated it altogether in a second pregnancy. It makes sense, since pregnancy hormones put a lot of additional stress on the liver.

3. Stressed adrenals

Your adrenals work in tandem with your liver and pancreas. During times of stress (like pregnancy), your adrenals call on the stored sugar in your liver for energy. If the adrenals are overly stressed, it can use up all of your stored sugar and then cause tissue breakdown for energy.

This is where a highly nutritious diet comes in. Eating enough for you and a growing baby is essential to keeping your adrenals from going into overdrive. This may be one reason that eating continuously during bouts of morning sickness and supporting adrenals with targeted supplements are good morning sickness remedies for some women.

4. H. Pylori overgrowth

This study found a strong association between an H. pylori infection and hyperemesis gravidarum, a very severe form of morning sickness. I’ve read stories of moms who had terrible morning sickness—even to the point of hyperemesis gravidarum—treat the H. pylori between pregnancies and then have zero sickness in their next pregnancy.

5. Low blood sugar

Many believe that low blood sugar from the extra caloric drain from the placenta causes morning sickness, though there are no studies to support this theory. However, many women find relief by not letting their blood sugar level drop too low, but it could also be related to stressed adrenals (which get even more stressed when blood sugars drop!).

6. Nutritional deficiency

Many moms who experience morning sickness in a first pregnancy have found that treating a magnesium deficiency helped relieve morning sickness in their next pregnancy. Our soils are depleted and our water is highly filtered, so most of us don’t get enough magnesium. However, it’s important to remember that vitamins and minerals work in tandem, and that you may have more than just a magnesium deficiency—in which case it’s important to be sure you are also getting enough B vitamins, calcium, vitamin D, vitamin K, and vitamin A too, preferably from food sources.

7. Electrolyte deficiency

Some believe that an electrolyte imbalance may cause or contribute to morning sickness, however, it may just be a side effect of vomiting. Some women have found relief in adding electrolytes to their diet by drinking this safe, DIY elixir.

8. Girl pregnancies

Some believe that carrying a girl can lead to more morning sickness, though there aren’t any studies to support this. In my case this was true, but it was also my second pregnancy (and I was more depleted).

9. Protection against toxins that could harm baby

Some experts believe that morning sickness is an evolutionary protection against food poisoning and components of foods that may be harmful during pregnancy. Some think baby’s susceptibility to toxins peaks at about 3 month gestation—the time when morning sickness usually starts to subside. This could be the reason that many pregnant women have aversions to alcohol, coffee, meat, eggs, and the like. On the other hand, some experts argue that this doesn’t make sense. Why? The foods that are typically eaten during the weeks of morning sickness are of little nutritional value (crackers, bread, etc.), while the foods that cause sickness are the best and most nutrient-dense pregnancy foods, like protein-rich meat, eggs, and fish.

10. Detoxing

This theory isn’t supported by hard science. But some think that our bodies go through a detoxing period during the first trimester. Why? In an effort to create the cleanest environment for our baby. So nausea and vomiting could be a side effect of that detoxification process.

What to Do If You’re Experiencing Morning Sickness

If you’ve been hit with morning sickness, there are plenty of natural remedies that can help ease the quease. Check out this post for some of the most tried-and-true methods out there.

Genevieve Howland

About the Author

Genevieve Howland is a doula and childbirth educator. She is the bestselling author of The Mama Natural Week-by-Week Guide to Pregnancy and Childbirth and creator of the Mama Natural Birth Course. A mother of three, graduate of the University of Colorado, and YouTuber with over 135,000,000 views, she helps mothers and moms-to-be lead healthier and more natural lives.


  1. Before I was pregnant peppermint worked to ease my stomach. Not so during pregnancy! Organic Ginger gummies were the only thing that helped. (Never worked before). I also kept a box of Jovial Foods sourdough crackers with me when I didn’t have a chance to eat – like in the car after my prenatal appointments. I didn’t want to be stuck miles from home and my only options were fast food. It’s amazing how so many different things work for different people!

  2. During my first pregnancy, which turned out to be a boy, I was so sick! Not vomiting but incredibly nauseous in the evening hours. I thought there had to be SOMETHING I could do to ease it. I pulled coconut oil 20 minutes each day and it cut down my nausea significantly. It also kept my teeth in excellent health through the pregnancy!
    If I missed a day my nausea would return in full force the following day.

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