Pregnancy

Current US guidelines recommend that pregnant women not use efavirenz during the first trimester of pregnancy. Also, any woman using efavirenz during the first trimester should be advised of the potential adverse events in the infant.

Animal studies of efavirenz have shown high rates of birth defects. Three out of 20 monkeys administered efavirenz during pregnancy gave birth to babies with significant abnormalities.

In early 2002, there was a report of an infant accidentally exposed to efavirenz during the early phase of gestation who was born with severe abnormalities attributed to neural tube defects.¹ There have also been four further reports of neural tube defects in children born to women exposed to efavirenz during the first three months of pregnancy, which led the manufacturer and the United States Food and Drug Administration to recommend in March 2005 that pregnant women avoid the drug.

However, it is difficult to be certain of the risks of the drug causing these birth defects, and whether their incidence is greater than would be expected in women not taking efavirenz. A systematic review and meta-analysis published in 2010 found that treatment with efavirenz during the first three months of pregnancy did not increase the risk of birth abnormalities. Amongst children born to women who received efavirenz in the first trimester, the overall incidence of birth abnormalities was 2.9%, and the prevalence of neural tube defects was 0.08%. Both figures are very close to the ranges reported in the general population in many developed and developing countries. However, many of the 16 observational studies in this analysis were limited by small sample size or did not control for confounding factors.²

Although a causal relationship has not been established between efavirenz and birth defects, women on efavirenz are advised to use barrier contraception for vaginal sex and an additional form of contraception, such as oral contraceptives. It is not known whether efavirenz is present in breast milk. The US CDC has recommended not using efavirenz if nursing.