Use of antihistamine medications during early pregnancy and selected birth defects: The National Birth Defects Prevention Study, 1997-2011.

Background: It is estimated that approximately 10-15% of pregnant women report antihistamine use during pregnancy. Although antihistamines are generally considered safe during pregnancy, results from published studies are inconsistent.

Methods: Using a case-control study design we analyzed 41,148 pregnancies (30,091 cases and 11,057 controls) from the National Birth Defects Prevention Study (1997-2011). Logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals for 64 birth defect groupings in relation to early pregnancy exposure to 14 distinct antihistamines. Models were adjusted for maternal age, race, parity, education level, prenatal care, folic acid use, smoking and alcohol use, and study site.

Results: Approximately 13% of cases and controls were exposed to an antihistamine during early pregnancy. Analyses were restricted to those defects where more than five cases were exposed to the antihistamine of interest, generating 340 analyses which yielded 20 (5.9%) significant positive associations (adjusted ORs ranging from 1.21 to 4.34).

Conclusions: Only a few of our findings were consistent with previous studies. There is a lack of strong evidence to conclude that birth defects are associated with exposure to antihistamines during early pregnancy.