Antipsychotic use early in pregnancy does not appear to meaningfully increase the risk of congenital malformations, according to findings from a large Medicaid pregnancy cohort.

A possible exception is with the use of risperidone; a small increase in the risk for malformations seen with the drug should be viewed as “an initial safety signal that will require confirmation in other studies,” Krista F. Huybrechts, PhD, of Brigham and Women’s Hospital and Harvard Medical School, Boston, and her colleagues reported online Aug. 17 in JAMA Psychiatry.

In a nationwide sample of more than 1.3 million pregnant women with a live-born infant between January 1, 2000 and December 31, 2010, the rate of congenital malformations identified within 90 days after delivery was 32.7 per 1,000 births among 1,331,724 women with no antipsychotic (AP) exposure, compared with a rate of 44.5 per 1,000 births among 9,258 women who filled at least one prescription for an atypical AP during their first trimester, and 38.2 per 1,000 in 733 women who filled at least one prescription for a typical AP during their first trimester, the researchers found (JAMA Psychiatry. 2016 Aug 17. doi: 10.1001/jamapsychiatry.2016.1520 ).

On unadjusted analyses, an overall risk was seen with atypical AP exposure (relative risk, 1.36), but not with typical AP exposure (RR, 1.17). After adjusting for confounding variables, the risk was not statistically significant (RR, 1.05 and 0.90, respectively). The findings were similar for cardiac malformations, the researchers noted.

When agents were analyzed individually, a small increased risk in overall malformations and cardiac malformations was found with risperidone (RR, 1.26 for each).

“The findings for risperidone should be viewed as an initial safety signal that will require confirmation in other studies,” the researchers wrote.

The study was supported by grants from the National Institutes of Health and the Swiss National Science Foundation. Dr. Huybrechts reported having no financial disclosures. Other authors disclosed receiving consulting fees and/or grant support from AstraZeneca, UCB, Alkermes, Bristol-Myers Squibb/Otsuka, Sunovion, Bayer, Ortho-McNeil Janssen, Pfizer, Forest Laboratories, Cephalon, GlaxoSmithKline, Takeda/Lundbeck, the National Institutes of Health, JDS Therapeutics, Noven Pharmaceuticals, and PamLab.