Objective: To study the impact of antihistamine use in early pregnancy on delivery outcome.
Methods: Using prospectively collected information on drug use in early pregnancy, delivery outcome was studied among 17 266 women with 17 776 deliveries and 18 197 infants. The analysis was performed according to the main reason for antihistamine use: nausea and vomiting in pregnancy and allergy.
Results: In the nausea and vomiting in pregnancy group, we found a significant increase in twin births and a significant reduction in preterm births, low birth weight and being small-for-gestational age among singletons. The perinatal death rate was reduced and the rate of congenital malformations was normal. A reduction was seen in the occurrence of congenital cardiovascular defects after the use of antihistamines. The odds ratio for specified cardiac defects, with the exception of ventricular and atrium septal defects, after the use of antihistamines for nausea and vomiting in pregnancy (0.54) was significantly lower than that for non-cardiovascular congenital malformations (0.95). No statistically significant effects on delivery outcome were seen after the use of antihistamine drugs for allergy. However, there was a non-significant tendency for a reduced risk for cardiovascular defects (odds ratio 0.71).
Conclusions: The beneficial effects on delivery outcome observed are most probably related to the underlying nausea and vomiting in pregnancy. There is no clear teratogenic effect of the antihistamines studied.