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Pregnant Despite Plan B

A prospective cohort study found no adverse pregnancy outcomes associated with Plan B emergency contraception.

Data indicate that the 0.75-mg levonorgestrel emergency contraception (LN-EC; Plan B) regimen has a failure rate of 0.2% to 3.0% per single act of coitus — higher than the failure rate associated with regular contraceptive methods. Investigators prospectively evaluated the effect of the Plan B regimen on pregnancy outcomes in women who presented to a single maternity hospital in China (where LN-EC has been available since 1998) during their first trimester of pregnancy. The investigators compared 332 women who had used LN-EC during the month that they conceived and 332 healthy pregnant women who were not exposed to LN-EC and were matched for age and date of last menstrual period. Neither group had been knowingly exposed to other potential teratogens during pregnancy. Mean age for both groups was 27.

The proportion of women who miscarried before 14 weeks’ gestation in the LN-EC and control groups did not differ significantly (10.3% and 8.6%), and four infants in each group had malformations. Although mean birth weight was significantly higher in the LN-EC group than in the control group (3416 g vs. 3345 g), no other significant differences in neonatal outcomes were found among the 272 infants born to mothers in the LN-EC group and the 298 infants born to mothers in the control group.

Comment: In 2006, the FDA approved over-the-counter sales of 0.75-mg levonorgestrel tablets to women aged 18 and older; younger women still needed a prescription, even though no significant biological or cognitive differences exist between young women aged 17 and 18. In March 2009, a federal court directed the FDA to permit Plan B’s manufacturer to make it available to women aged 17 and older without a prescription. Given the ruling, the FDA’s position is now more in line with that of major professional organizations. The findings of this large cohort study provide additional reassurance that, should pregnancy occur in women who take over-the-counter LN-EC, the developing fetus will not be harmed. Nonetheless, a clinician’s primary objective remains to support the use of reliable contraceptive methods among sexually active women, thereby minimizing the need for emergency contraception.

— Alain Joffe, MD, MPH, FAAP

Published in Journal Watch Pediatrics and Adolescent Medicine May 20, 2009

Citation(s):

Zhang L et al. Pregnancy outcome after levonorgestrel-only emergency contraception failure: A prospective cohort study. Hum Reprod 2009 Mar 31; [e-pub ahead of print]. (http://dx.doi.org/10.1093/humrep/dep076)