One in 10 pregnant women experience severe nausea.
Many doctors prescribe Zofran, although some women have shied away from it because a small study previously suggested the drug might raise the risk of cleft palate.
The new study of more than 600,000 pregnancies found no evidence of major birth-related problems.
The study appears in the current New England Journal of Medicine.
Doctors recommend women try treating morning sickness with crackers, ginger ale, and certain B vitamins first, and only use medications as a last resort.