Up to 80% of pregnant women have nausea and vomiting to some extent. Nausea and vomiting are most common and most severe during the 1st trimester. Although commonly called morning sickness, such symptoms may occur at any time during the day. Symptoms vary from mild to severe.

Hyperemesis gravidarum is a severe, persistent form of pregnancy-related vomiting. Women with hyperemesis gravidarum vomit so much that they lose weight and become dehydrated. Such women may not consume enough food to provide the body with energy. Then the body breaks down fats, resulting in a buildup of waste products (ketones) called ketosis. Ketosis can cause fatigue, bad breath, dizziness, and other symptoms. Women with hyperemesis gravidarum often become so dehydrated that the balance of electrolytes, needed to keep the body functioning normally, is upset (see Electrolyte Balance: Electrolytes).

If women vomit occasionally but gain weight and are not dehydrated, they do not have hyperemesis gravidarum. Morning sickness and hyperemesis gravidarum tend to resolve during the 2nd trimester.

Causes

Usually, nausea and vomiting during pregnancy are related to the pregnancy. However, sometimes they result from a disorder unrelated to the pregnancy.

Common causes: The most common causes of nausea and vomiting are

• Morning sickness (most common)
• Hyperemesis gravidarum
• Gastroenteritis (infection of the digestive tract)

Why morning sickness and hyperemesis gravidarum occur during pregnancy is unclear. However, these symptoms may occur because during pregnancy, levels of two hormones increase: human chorionic gonadotropin (hCG), which is produced by the placenta early in pregnancy, and estrogen, which helps maintain the pregnancy. Estrogen levels are particularly high in women with hyperemesis gravidarum. Also, hormones such as progesterone (produced continuously during pregnancy) may slow the movement of the stomach's contents, possibly contributing to nausea and vomiting. Psychologic factors may also be involved.

Less common causes: Occasionally, prenatal vitamins with iron cause nausea. Rarely, severe, persistent vomiting results from a hydatidiform mole (overgrowth of tissue from the placenta).

Causes unrelated to the pregnancy include

• Disorders of the abdomen such as appendicitis, a blockage in the intestine (bowel obstruction), or inflammation of the gallbladder (cholecystitis)
• Brain disorders such as migraine, bleeding within the brain (intracranial hemorrhage), and increased pressure within the brain (increased intracranial pressure)

However, these disorders usually cause other symptoms that are more prominent, such as abdominal pain or headaches.

Evaluation

Doctors first try to determine whether nausea and vomiting are caused by a serious disorder. Morning sickness and hyperemesis gravidarum are diagnosed only after other causes are ruled out.

Warning signs: In pregnant women who are vomiting, the following symptoms are cause for concern:

• Abdominal pain
• Signs of dehydration, such as decreased urination, decreased sweating, increased thirst, a dry mouth, a racing heart, and dizziness when standing up
• Fever
• Vomit that is bloody, black (resembling coffee grounds), or green
• No movement of the fetus if the fetus is older than 24 weeks
• Confusion, weakness or numbness of one side of the body, speech or vision problems, or sluggishness―symptoms that suggest bleeding within the brain

When to see a doctor: Women with warning signs should see a doctor right away, as should those with vomiting that is particularly severe or is worsening. Women without warning signs should talk to their doctor. The doctor can help them decide whether and how quickly they need to be seen based on the nature and severity of their symptoms. Women who have mild to moderate nausea and vomiting, have not lost weight, and are able to keep some liquids down may not need to see a doctor unless their symptoms worsen.

What the doctor does: Doctors ask about symptoms and the medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause and the tests that may need to be done (see Symptoms During Pregnancy: Some Causes and Features of Nausea and Vomiting During Early Pregnancy).

Doctors ask about the vomiting:

• When it started
• How long it lasts
• How many times a day it occurs
• Whether anything relieves or makes it worse
• What the vomit looks like
• How much there is

The woman is asked whether she has other symptoms, particularly abdominal pain, diarrhea, and constipation, and how her symptoms have affected her and her family—whether she can work and care for her children. The woman is also asked about vomiting in previous pregnancies, about previous abdominal surgery, and use of drugs that may contribute to vomiting.

During the physical examination, doctors first look for signs of serious disorders, such as blood pressure that is too low or too high, fever, confusion, and sluggishness. A pelvic examination is done to check for evidence of a hydatidiform mole and other abnormalities.

This information helps doctors determine whether vomiting results from the pregnancy or another, unrelated disorder. For example, vomiting probably results from the pregnancy if it

• Began during the 1st trimester
• Lasts or recurs over several days to weeks
• Is not accompanied by abdominal pain

Vomiting probably results from another disorder if it

• Began after the 1st trimester
• Is accompanied by abdominal pain, diarrhea, or both

PrintOpen table in new window
Some Causes and Features of Nausea and Vomiting During Early Pregnancy Cause Common Features* Tests Related to the pregnancy (obstetric) Morning sickness Mild nausea and vomiting that comes and goes and that occurs at varying times throughout the day, primarily during the 1st trimester A doctor's examination Hyperemesis gravidarum Frequent, persistent nausea and vomiting Inability to consume enough fluids, food, or both Usually signs of dehydration, such as decreased urination, decreased sweating, a dry mouth, increased thirst, a racing heart, and dizziness when standing up Weight loss Blood tests to check for signs of dehydration and chemical imbalances by measuring levels of electrolytes, blood urea nitrogen (BUN), and creatinine Urine tests to measure ketones (produced when not enough food is consumed and the body breaks down fats for energy) If vomiting persists, possibly blood tests to evaluate the liver (liver function tests) and ultrasonography of the pelvis A hydatidiform mole (overgrowth of tissue from the placenta) A uterus that is larger than expected No heartbeat or movement detected in the fetus during the 2nd trimester Sometimes high blood pressure, swelling of the feet or hands, vaginal bleeding, or passage of tissue that resembles a bunch of grapes Measurement of blood pressure Blood tests to measure human chorionic gonadotropin (hCG―a hormone produced by the placenta early in pregnancy) Ultrasonography of the pelvis A biopsy if no pregnancy is seen in the uterus Not related to the pregnancy Gastroenteritis Vomiting that began suddenly, often accompanied by diarrhea Sometimes recent contact with infected people or animals or recent consumption of undercooked, contaminated food or contaminated water A doctor's examination Sometimes examination and culture of stool A blockage in the intestine (bowel obstruction) Symptoms that begin suddenly, usually in women who have had abdominal surgery in the past Crampy pain and a swollen abdomen X-rays and ultrasonography of the abdomen Possibly CT (if x-ray and ultrasound results are unclear) A urinary tract infection or kidney infection (pyelonephritis) An urge to urinate often (frequency), a compelling need to urinate immediately (urgency), or difficulty starting to urinate (hesitancy) With kidney infection, pain in the side and fever Urine tests (urinalysis) and culture *Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present. CT = computed tomography.

Testing: Doctors often use a handheld Doppler ultrasound device, placed on the woman's abdomen, to check for a heartbeat in the fetus. If no heartbeat is detected by the time they should be (at about 11 weeks), a hydatidiform mole is possible. If the woman is vomiting often or appears dehydrated or if a hydatidiform mole is possible, tests are usually done. Which tests are done depend on the cause doctors suspect:

• Hyperemesis gravidarum: Urine tests (to measure ketone levels) and possibly blood tests (to measure electrolyte levels and other substances)
• A hydatidiform mole: Ultrasonography of the pelvis
• A disorder unrelated to the pregnancy: Tests specific for that disorder

Treatment

If vomiting is due to a disorder, that disorder is treated. If vomiting is related to pregnancy, some changes in diet or eating habits may help:

• Drinking or eating small amounts more frequently (5 or 6 small meals a day)
• Eating before getting hungry
• Eating only bland foods, such as bananas, rice, applesauce, and dry toast (called the BRAT diet)
• Keeping crackers by the bed and eating one or two before getting up
• Drinking carbonated drinks (sodas)

If vomiting results in dehydration, the woman may be given fluids intravenously. If vomiting persists, she may be hospitalized. She may be given sugar (glucose), electrolytes, and occasionally vitamins intravenously with the fluids. After vomiting has subsided, she is given fluids by mouth. If she can keep these fluids down, she can begin eating frequent, small portions of bland foods. The size of the portions is increased as the woman can tolerate more food.

If needed, drugs to relieve nausea (antiemetic drugs) are given. Doctors choose drugs that appear to be safe during early pregnancy. Vitamin B₆ is used first. If it is ineffective, another drug (doxylamineSome Trade Names
UNISOM
, metoclopramideSome Trade Names
REGLAN
, ondansetronSome Trade Names
ZOFRAN
, or promethazine) is also given.

Ginger, acupuncture, motion sickness bands, and hypnosis may help, as may switching from prenatal vitamins to children's chewable vitamins with folate.

Rarely, weight loss continues and symptoms persist despite treatment. Then the woman is fed through a tube passed through the nose and down the throat to the small intestine (see Undernutrition: Tube feeding). Tube feeding is continued for as long as necessary.

Key Points

• Usually, nausea and vomiting during pregnancy do not cause weight loss or other problems, and they resolve before or during the 2nd trimester.
• Hyperemesis gravidarum, a severe, persistent form of pregnancy-related vomiting, is less common and can cause dehydration and weight loss.
• Nausea and vomiting may be due to disorders not related to pregnancy, such as gastroenteritis, a urinary tract infection, or, rarely, a blockage in the intestine.
• Modifying the diet may help relieve mild nausea and vomiting that are related to pregnancy.
• If women with hyperemesis gravidarum become dehydrated, they may need to be given fluids intravenously.

Last full review/revision May 2012 by R. Phillips Heine, MD; R. Phillips Heine, MD