Zolpidem (Ambien) in pregnancy: placental passage and outcome.

To examine the extent and clinical sequelae of fetal exposure to zolpidem, a commonly prescribed hypnotic agent. Pregnant women with psychiatric illness participating in a study of psychotropic pharmacokinetics were included. Zolpidem concentrations were analyzed in maternal and umbilical cord plasma collected at delivery. Outcomes were compared between the zolpidem-exposed group and a 1:1 matched comparator group. Forty-five women taking zolpidem during pregnancy were studied. Rates of preterm delivery and low birth weight were 26.7% and 15.6% respectively in the zolpidem-exposed group versus 13.3% and 4.4% in the matched comparator group, but no significant differences were found. The ratio of umbilical cord to maternal plasma zolpidem concentrations in 6 pairs ranged from 0.48 to 2.75. Zolpidem crosses the human placenta and rapidly clears the fetal circulation. Pregnant women with psychiatric illness treated with zolpidem may have less optimal obstetrical outcome, though it is unclear if this was related to the medication.