The FDA Friday approved Makena, a pregnancy hormone injection to reduce the risk of delivering a baby before 37 weeks of gestation.
Twelve percent of women give birth prematurely. Those babies are more likely to develop lung problems and learning disabilities.
In trials, weekly Makena injections lowered the rate of delivering prematurely, but did not eliminate the risk.
The FDA approval is only for women who have already had a pre-term baby.