The Facts

Many pregnant women (about 70% to 85%) experience a period of nausea and vomiting. In the vast majority of cases, it's unpleasant but not dangerous.

About 1% of expectant mothers will vomit so severely that they lose weight and become dehydrated, requiring hospital treatment. This severe form of morning sickness is called hyperemesis gravidarum. Although this condition could be life-threatening if left untreated, it can be remedied by treatment during a brief hospital stay.

When a woman has morning sickness, it can be severe enough that it affects usual daily activities (e.g., working, caring for children). Although it's called "morning sickness," the nausea and vomiting may occur at any time of day.


While the exact causes of morning sickness aren't known, it's probably linked to pregnancy hormones. Women who suffer morning sickness tend to have higher levels of these hormones than those who don't.

It's possible that nausea and vomiting during pregnancy is an ancient mechanism for protecting the fetus from poisons. With the enormously rich and varied diet we eat today compared to our ancestors, it's no surprise that such a protective system could become a bit confused and start rejecting all sorts of healthy food.

One piece of evidence for this idea can be found in research showing that women who suffer from vomiting during pregnancy actually have lower rates of miscarriage than women who don't. Research shows higher levels of two hormones (thyroxine and human chorionic gonadotropin) in women with morning sickness. Women who suffer nausea from the birth control pill are more likely to develop morning sickness during pregnancy.

Symptoms and Complications

Morning sickness doesn't necessarily strike in the morning. While vomiting is at its worst for many women between 9 am and noon, it can continue through the day, or may even appear on a completely different schedule. Vomiting is more likely after meals.

This is essentially a problem of early pregnancy. A few women begin vomiting within days of conception, but typically morning sickness starts about six weeks after the end of the last menstruation. Actual vomiting is often preceded by nausea lasting a week or two.

About 80% of sufferers will feel better by Week 12 of the pregnancy, and most will stop vomiting by the end of Week 16. Occasionally, some nausea returns just before delivery. Like morning sickness itself, this is in no way a dangerous or bad sign. A very few women have morning sickness throughout pregnancy - again, this is unfortunate but not dangerous.

Hyperemesis gravidarum is essentially morning sickness so severe that it affects the mother's nutrition and, therefore, the baby's health. It can also lead to liver or kidney damage. Fortunately, most pregnant women are closely monitored by their doctors, and these complications are almost always caught early on.

Making the Diagnosis

Morning sickness isn't a disease and doesn't need elaborate diagnostic tests. If a woman is pregnant and is throwing up (or constantly feels like throwing up), a doctor will probably tell her that she has morning sickness. It's still morning sickness if she's only throwing up in the evenings or at other times during the day.

No matter how severe the vomiting, a woman is only diagnosed with hyperemesis gravidarum if she is losing weight or showing signs of severe dehydration.

Treatment and Prevention

The best way to manage morning sickness is to start with non-drug measures. Here are some suggestions that many women have found to help:

  • try snacking or "grazing" throughout the day instead of eating large meals
  • avoid rich and fatty foods - try plain carbohydrates like potatoes and rice
  • try soups, jelly, colas and other sodas, and sugared herbal teas
  • eat a few crackers while in bed before getting up in the morning
  • carry salted crackers or some similar food around - it's important not to let the stomach get completely empty, as this can increase nausea
  • try to avoid things that trigger nausea, like certain food smells
  • if taking prenatal vitamins containing iron, try switching brands to see if symptoms grow milder
  • avoid prenatal vitamins and take folic acid only
  • avoid cooking if the cooking odour worsens your symptoms
  • avoid acidic foods
  • avoid fried foods
  • do not lie down right after eating

There are other suggestions floating around in the media and on the Internet. A woman should talk to her doctor before trying herbal or vitamin-based remedies. Many people recommend the herb ginger, but its safety and effectiveness have not been proven in scientific studies.

Some women use acupressure, a fairly common home remedy for nausea. The standard device is an elastic wristband with a button on it. The button is placed over the Neiguan point, about two inches above the inner wrist. Compressing this point is considered by many to relieve nausea, and ship passengers hoping to avoid seasickness often wear these devices. However, the devices have not been well studied for morning sickness.

If non-drug measures are ineffective, a doctor may prescribe doxylamine-vitamin B6* to control morning sickness. Many women are concerned about taking medications during pregnancy due to the possible risk to the fetus and birth defects. It is important to keep in mind that all women have about a 3% chance of having a child with a birth defect. Studies have shown that doxylamine-vitamin B6 does not pose a risk to the fetus and is not associated with an increase in birth defects. Women with hyperemesis gravidarum may also need to receive intravenous (IV) feeding or fluid replacement to treat dehydration.


*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.