What is Pregnancy, nausea?

Pregnancy, nausea

What are nausea and vomiting in early pregnancy?

During the first 12 weeks of pregnancy (called the first trimester), it's normal to have what is commonly called "morning sickness": feeling sick to your stomach and vomiting. This is unpleasant, but it most likely won't hurt you or your baby. However, a few women do have serious nausea and vomiting during pregnancy and need medical treatment.

Key points about nausea and vomiting in early pregnancy

It's normal to feel sick to your stomach and vomit during the first few months of pregnancy. Most pregnant women do.
Nausea and vomiting won't usually harm you or your unborn baby.
You may feel sick to your stomach at any time of the day, not just in the mornings.
About 1 in 200 pregnant women have severe nausea and vomiting that can be dangerous to their health and their baby's health. Doctors call this condition hyperemesis gravidarum.
Nausea and vomiting usually stop after about 12 weeks of pregnancy. But 1 in 10 pregnant women still have morning sickness after 20 weeks.

There are lots of myths about nausea and vomiting in early pregnancy. See how much you know by taking our quiz, Myths about nausea and vomiting in early pregnancy.

What's normal

Feeling sick to your stomach and vomiting is often the first sign that you're pregnant. In fact, you may not have realized you were pregnant until you started to feel like this.

Feeling sick to your stomach can make you feel miserable. But it's a normal part of early pregnancy.

Almost all pregnant women have some nausea, although not everyone vomits. These symptoms usually begin around six weeks after the start of your last period.

Source:
Whitehead SA, Andrews PLR, Chamberlain GVP.
Characterisation of nausea and vomiting in early pregnancy: a survey of 1000 women.
Journal of Obstetrics and Gynaecology. 1992; 12: 364-369.

Source:
Gadsby R, Barnie-Adshead AM, Jagger C.
A prospective study of nausea and vomiting during pregnancy.
British Journal of General Practice. 1993; 43: 245-248.

Even if you vomit two or three times a day, usually you can keep some food down and won't lose weight during the first few months of pregnancy.

A survey of 1,000 women in the first half of their pregnancy gives us some idea of how you may feel during your pregnancy:

Source:
Whitehead SA, Andrews PLR, Chamberlain GVP.
Characterisation of nausea and vomiting in early pregnancy: a survey of 1000 women.
Journal of Obstetrics and Gynaecology. 1992; 12: 364-369.

About 6 in 10 pregnant women feel sick to their stomach every day
About half of all pregnant women vomit, but only about 1 in 5 vomit day
Although nausea and vomiting in pregnancy is often called morning sickness, only about 1 in 5 women say that their symptoms stop by noon
Many women feel sick to their stomach and vomit at any time of the day, although they usually feel worse in the morning
The earlier in your pregnancy that symptoms start (for example, around the fourth week), the more frequent they are likely to be.

Triggers for nausea and vomiting in early pregnancy

Many women notice that certain things make them feel worse, or "trigger" their symptoms. Here are some common triggers:

Source:
Heinrichs L.
Linking olfaction with nausea and vomiting of pregnancy, recurrent abortion, hyperemesis gravidarum, and migraine headache.
American Journal of Obstetrics and Gynecology. 2002; 186 (supplement 1): S215-S219.

Source:
Furneaux EC, Langley-Evans AJ, Langley-Evans SC.
Nausea and vomiting of pregnancy: endocrine basis and contribution to pregnancy outcome.
Obstetrical and Gynecological Survey. 2001; 56: 775-782.

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Smelling certain odors, especially coffee, perfumes, cigarette smoke and gasoline
Cooking and eating certain foods, especially meats, fatty meals or spicy meals
Becoming very tired
Feeling anxious or worried
Changing position quickly (for example, standing up fast).

We know very little about why some pregnant women get morning sickness and others don't. But it's nothing to worry about. In fact, women who do feel sick are less likely to have a miscarriage than women who don't feel sick.

Source:
Weigel RM, Weigel MM.
Nausea and vomiting of early pregnancy and pregnancy outcome: a meta-analytical review.
British Journal of Obstetrics and Gynaecology. 1989; 96: 1312-1318.

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What's not normal

It's normal to feel sick to your stomach and vomit when you're pregnant. But it's not normal to feel so sick that you can't hold down any food or fluids for days on end.

Here's what we know about severe nausea and vomiting in pregnancy, which is called

hyperemesis gravidarum
Hyperemesis gravidarum is very severe nausea and vomiting during pregnancy. About 1 in 100 pregnant women get this condition. If you have hyperemesis gravidarum, you throw up so much that your health and your baby's health may be in danger if you don't have treatment. Women with this condition may have to go into hospital.

hyperemesis gravidarum.

About 1 in 200 pregnant women have severe nausea and vomiting.

Source:
Eliakim R, Abulafia O, Sherer DM.
Hyperemesis gravidarum: a current review.
American Journal of Perinatology. 2000; 17: 207-218.

⁶
If you have hyperemesis gravidarum, your vomiting may be so bad that you lose weight, often about 10 pounds. To learn more, see What are the symptoms of normal and severe nausea and vomiting in early pregnancy?
When you're pregnant, it's normal to feel very tired and emotional and to be worried about your unborn baby. You may feel even more emotional if you also have severe nausea and vomiting.
You might be upset that you feel sick to your stomach, especially if you were looking forward to your pregnancy.
Your symptoms may seem to clear up after your third month of pregnancy, but they might come back from time to time.
You may be treated in the hospital to avoid becoming

dehydrated
When you're dehydrated, you don't have enough fluid in your blood. This could be because you're not drinking enough or because you're losing water by sweating or having diarrhea.

dehydrated and to make sure you get enough of the right nutrients. To learn more, see What happens in the hospital?
Unborn babies are usually not harmed by severe nausea and vomiting. There's a small chance that you will lose weight or have a small baby, but if you receive treatment, this probably won't happen.
If you feel very sick to your stomach and vomit during one pregnancy, you have about a 50 percent chance of feeling like this during another pregnancy.

Source:
Baron TH, Ramirez B, Richter JE.
Gastrointestinal motility disorders during pregnancy.
Annals of Internal Medicine. 1993; 118: 366-375.

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Why does it happen?

Doctors are not sure why most women feel sick to their stomach and vomit when they're pregnant. But some doctors think morning sickness may protect your baby from threats in the environment. Being pregnant may make you more sensitive to these dangers.

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For example, when you are near car or gas fumes, you may move away because the smell makes you feel queasy. This may keep poisons out of your body and away from your unborn baby.

Nausea and vomiting may go away when you're about three months pregnant because your baby has passed through important stages of development. Poisons are generally less harmful to your baby later in your pregnancy.

What causes it?

Here are some of the most popular theories that explain why pregnant women feel sick totheir stomach and vomit.

Many doctors think that the sudden rise of a

hormones
Hormones are chemicals that are made in certain parts of the body. They travel through the bloodstream and have an effect on other parts of the body. For example, the female sex hormone estrogen is made in a woman's ovaries. Estrogen has many different effects on a woman's body. It makes the breasts grow at puberty and helps control periods. It is also needed to get pregnant.

hormone called human chorionic gonadotrophin (HCG) during early pregnancy makes women feel sick to their stomach.

Source:
Furneaux EC, Langley-Evans AJ, Langley-Evans SC.
Nausea and vomiting of pregnancy: endocrine basis and contribution to pregnancy outcome.
Obstetrical and Gynecological Survey. 2001; 56: 775-782.

⁴ There seems to be no link, however, between how much HCG you have in your blood and how bad your nausea and vomiting will be. Still, you are more likely to feel sick to your stomach and vomit if you're expecting twins, when levels of this hormone rise higher than if you're expecting a single baby. You're also more likely to feel very sick to your stomach if you have a hydatidiform mole, also called molar pregnancy. To learn more, see Molar pregnancy.
HCG looks a lot like another hormone (thyroid stimulating hormone or TSH) that tells the body to make more

thyroid gland
Your thyroid gland is a small organ that sits in your neck, just in front of your windpipe. It sends out a hormone called thyroxine. This acts on receptors within cells. By acting on the receptors it gives the cells a message to speed up their metabolism and work harder.

thyroid hormone. So HCG can also send a message to the body to make more thyroid hormone. It is possible that high levels of thyroid hormone are what causes the nausea and vomiting.
Not getting enough of some vitamins and minerals, such as vitamin B-6, may cause nausea and vomiting.

Source:
University of Texas at Austin School of Nursing.
Recommendations for the evaluation and management of nausea and vomiting of early pregnancy.
October 2002. Available at http://www.guideline.gov (accessed on 2 September 2008).

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Why me?

Doctors don't know why some women feel sick to their stomach and vomit during pregnancy and others feel fine. They also don't know why one pregnant woman has only mild nausea while another vomits several times a day for many months.

But there are certain factors that increase your chances of having nausea and vomiting when you're pregnant. Doctors call these risk factors. To learn more, see Risk factors for nausea and vomiting in early pregnancy.

Sources for the information on this page:

Whitehead SA, Andrews PLR, Chamberlain GVP.Characterisation of nausea and vomiting in early pregnancy: a survey of 1000 women.Journal of Obstetrics and Gynaecology. 1992; 12: 364-369.

Gadsby R, Barnie-Adshead AM, Jagger C.A prospective study of nausea and vomiting during pregnancy.British Journal of General Practice. 1993; 43: 245-248.

Heinrichs L.Linking olfaction with nausea and vomiting of pregnancy, recurrent abortion, hyperemesis gravidarum, and migraine headache.American Journal of Obstetrics and Gynecology. 2002; 186 (supplement 1): S215-S219.

Furneaux EC, Langley-Evans AJ, Langley-Evans SC.Nausea and vomiting of pregnancy: endocrine basis and contribution to pregnancy outcome.Obstetrical and Gynecological Survey. 2001; 56: 775-782.

Weigel RM, Weigel MM.Nausea and vomiting of early pregnancy and pregnancy outcome: a meta-analytical review.British Journal of Obstetrics and Gynaecology. 1989; 96: 1312-1318.

Eliakim R, Abulafia O, Sherer DM.Hyperemesis gravidarum: a current review.American Journal of Perinatology. 2000; 17: 207-218.

Baron TH, Ramirez B, Richter JE.Gastrointestinal motility disorders during pregnancy.Annals of Internal Medicine. 1993; 118: 366-375.

University of Texas at Austin School of Nursing.Recommendations for the evaluation and management of nausea and vomiting of early pregnancy.October 2002. Available at http://www.guideline.gov (accessed on 2 September 2008).

This information was last updated on May 12, 2009

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