Is lack of morning sickness teratogenic? A prospective controlled study.

Background: Case-control studies have suggested that the nausea and vomiting of pregnancy (NVP) may have a protective effect against specific malformations. These suggestions have been interpreted as if the lack of NVP may put mothers at an increased teratogenic risk.

Methods: A prospective, cohort-controlled study was done comparing pregnancy outcome in women not experiencing NVP with those experiencing NVP at two levels of clinical severity. Women who called the Motherisk program about first-trimester exposure to drugs and who had not experienced NVP were included as the study group. The NVP Healthline enrolled two control groups of women with NVP treated with a doxylamine-pyridoxine combination for morning sickness. These women were exposed during the first trimester of gestation to either higher than the standard dose (5-12 tablets/day) or a standard dose (1-4 tablets/day) of doxylamine-pyridoxine. The women in all three groups were followed up four to six months after the expected date of birth to ascertain pregnancy outcomes and child health.

Results: There were no major malformations among offspring of 130 women not experiencing NVP. There were two major malformations among 246 women experiencing NVP. The two control groups of women with NVP had similar distributions of gestational ages, birth rates, as well as rates of miscarriages and stillbirths, as in the no-NVP group.

Conclusions: This study did not show an association between lack of NVP and an increase in the overall rates of major malformations.