Nausea and Vomiting in Pregnancy

Posted by Graham McMahon • October 15th, 2010

The latest article in our Clinical Practice series, “Nausea and Vomiting in Pregnancy,” comes from Jennifer R. Niebyl, M.D., from the University of Iowa Hospitals and Clinics.

About 50% of women have nausea and vomiting in early pregnancy, and an additional 25% have nausea alone. The popular term “morning sickness” is a misnomer, as it often persists throughout the day. In about 35% of those who have this condition, nausea and vomiting are clinically significant, resulting in lost work time and negatively affecting family relationships.

Clinical Pearls

When do nausea and vomiting in pregnancy most typically resolve?

The onset of the nausea is within four weeks of the last menstrual period in most patients. The problem typically peaks at approximately 9 weeks of gestation. Sixty percent of cases resolve by the end of the first trimester and 91%, by 20 weeks gestation.

What are some protective factors against nausea and vomiting in pregnancy?

Nausea and vomiting are less common in older women, multiparous women, and smokers, an observation that has been attributed to their smaller placental volumes.

Morning Report Questions

Q: How should abnormalities of thyroid function be interpreted and managed in women with nausea and vomiting in pregnancy?

A: As hCG cross-reacts with TSH and stimulates the thyroid gland, TSH is typically suppressed in these patients. An ultrasound should be performed to detect multiple gestation or hydatidiform mole. This apparent hyperthyroidism usually resolves spontaneously, and treatment with propylthiouracil does not help the nausea and vomiting.

Q: What medication is recommended as first-line treatment for nausea and vomiting in pregnancy?

A: Oral vitamin B6 and doxylamine are available over the counter in the United States. The combination has been well studied in over 6000 patients and controls, with no evidence of teratogenicity, and, in randomized trials, a 70% reduction in nausea and vomiting. It is recommended by the American College of Obstetricians and Gynecologists as first-line therapy for nausea and vomiting in pregnancy.

Table 1. Pharmacologic Treatment of Nausea and Vomiting in Pregnancy.

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