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Nausea and vomiting are common during pregnancy; they are thought to occur because estrogen levels increase rapidly. Although vomiting in the morning (morning sickness) is typical, nausea or vomiting can occur at any time. These symptoms are most common and most severe during the 1st trimester of pregnancy. Hyperemesis gravidarum (see Abnormalities of Pregnancy: Hyperemesis Gravidarum) is persistent pregnancy-induced vomiting that causes significant dehydration, often with electrolyte abnormalities or ketosis. Occasionally, prenatal vitamin preparations with iron cause nausea. Rarely, severe, persistent vomiting may result from hydatidiform mole. Vomiting can also result from many nonobstetric disorders.

Evaluation

Vomiting is less likely to be due to pregnancy if it begins after the 1st trimester of pregnancy. Vomiting is likely to be due to pregnancy if it lasts several days to weeks, abdominal pain is absent, and other apparent causes for vomiting are absent. If hyperemesis gravidarum is suspected, urine ketones are measured; if symptoms are particularly severe or persistent, serum electrolytes are measured. A normal intrauterine pregnancy should be confirmed to rule out hydatidiform mole. Other tests are done based on clinically suspected nonobstetric disorders.

Treatment

Pregnancy-induced vomiting may be relieved by drinking or eating frequently (5 or 6 small meals/day), but only small amounts of bland foods (eg, crackers, soft drinks, BRAT diet [bananas, rice, applesauce, dry toast]) should be eaten. Eating before rising may help. If dehydration (eg, due to hyperemesis gravidarum) is suspected, normal saline or Ringer's lactate is given IV, and identified electrolyte abnormalities are corrected.

The antiemetics doxylamine Some Trade Names
GOOD SENSE SLEEP AID
UNISOM SLEEPTABS
Click for Drug Monograph
(10 mg po at bedtime), metoclopramide Some Trade Names
REGLAN
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(10 mg po or IV q 8 h as needed), ondansetron Some Trade Names
ZOFRAN
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(8 mg po or IM q 12 h as needed), promethazine Some Trade Names
PHENERGAN
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(12.5 to 25 mg po, IM, or rectally q 6 h as needed), and pyridoxine (vitamin B₆; 10 to 25 mg po tid as needed) are extensively used to relieve nausea and vomiting during the 1st trimester without evidence of adverse effects on the fetus; these drugs can be used safely throughout pregnancy. Ginger, acupuncture, motion sickness bands, and hypnosis may help, as may switching from prenatal vitamins to a children's chewable vitamin with folate.

Last full review/revision November 2005

Content last modified November 2005