This is a double-blinded, placebo-controlled, multicenter, randomized clinical trial of 17P versus placebo. The primary outcome measure will be the percentage of each group reaching either a gestational age of 34w0d or documentation of fetal lung maturity at 32w0d to 33w6d. Secondary outcomes will include the latency period for each group and the percentage of newborns in each group who have major neonatal morbidity or death.