Side effects were reported by 11.2% of the women. There were no significant betweengroup differences in the rates of any of the reported side effects. The most common side effects were nausea (7.3% in the vitamin group and 6.8% in the placebo group, P = 0.31) and vomiting (4.4% in the vitamin group and 4.0% in the placebo group, P = 0.23).