Between 50 and 80 percent of women experience nausea and vomiting during the first trimester of pregnancy. Many complementary and alternative therapies are perceived to be safe and are used by many pregnant women, but little is known about their relative effectiveness. At least three randomized controlled trials have found ginger to be more effective than placebo in short-term trials. No adverse effects were apparent for mother or baby; however, animal studies have associated ginger with early embryo loss and accelerated growth in surviving embryos. Smith and colleagues compared ginger with vitamin B₆ in the treatment of nausea and vomiting in women before the 16th week of pregnancy.

The study included women attending an Australian teaching hospital for obstetric care. Participants were women with nausea or vomiting who were at eight to 16 weeks' gestation as confirmed by ultrasonography. Women were excluded from the study if they had any signs of dehydration or indications of other pathology causing nausea or vomiting or if they had a known allergy to ginger or vitamin B₆. The 291 women were randomly allocated to receive ginger (350 mg) or vitamin B₆ (25 mg) three times daily for three weeks. The two preparations appeared identical, and participants and physicians were blinded to treatment allocation. All women provided demographic and health status information plus a standardized index of nausea and vomiting before randomization. Health status and the nausea/vomiting index were reassessed at days 7, 14, and 21. Data also were gathered concerning side effects and adverse pregnancy outcomes.

The 146 women randomized to receive ginger were comparable with the 145 women assigned to receive vitamin B₆. At the end of the three-week trial, 82 percent of participants had completed and returned their data. Both treatments were effective in reducing symptoms. The two treatments appeared to be equivalent in overall scores and in the proportion of women reporting freedom from symptoms. Improvements were reported by 68 women (53 percent) receiving ginger compared with 69 women (55 percent) receiving vitamin B₆. Women reported tolerating both medicines well, but belching was significantly more common with ginger (9 percent compared with zero percent). Dry retching after swallowing the tablet was reported by about one half of the women in each group. Pregnancy complications and outcomes were similar in the two treatment groups.

The authors conclude that ginger reduces nausea and vomiting in early pregnancy and is comparable in effect to vitamin B₆.