Last week, an independent FDA advisory panel narrowly voted to recommend the agency withdraw the only drug approved for preventing recurrent premature birth in pregnant women with a prior history, Makena, from the market.

Premature, or preterm birth, refers to childbirth before the 37th week of pregnancy, about three weeks before the due date. Many premature infants do not survive, and those who do are at high risk of a wide range of long-term medical complications. The earlier the birth, the greater these risks are.

While the 9-7 vote of the advisory panel is not binding, the FDA follows such recommendations about 80% of the time.

Makena is an injectable form of the synthetic progesterone hormone 17α hydroxyprogesterone caproate, often called 17P. It was fast-tracked to approval in 2011 based on promising results from a 2003 study of 463 pregnant women with a history of preterm birth in which Makena was found to significantly reduce the risk of recurrent preterm delivery. As a condition of accelerated approval, however, manufacturer AMAG Pharmaceuticals was required to conduct a larger confirmatory study.

Published in late October, the follow-up trial of approximately 1,700 women, in contrast, “did not demonstrate a statistically significant difference between the treatment and placebo,” according to a manufacturer statement. 

Based on these results, nine advisory panel members recommended withdrawing Makena while seven voted to maintain accelerated approval and require additional confirmatory studies.

Christopher Zahn, American College of Obstetricians and Gynecologists vice president for practice, told NPR that the confirmatory study involved many women at considerably lower risk of preterm birth than in the first study, complicating direct comparisons.

Zahn expressed concern that withdrawal of Makena could increase preterm births “which creates a host of tragic problems for babies.” 

Makena is not intended for multiple-birth pregnancies.