Relationship Between Plasma Concentration of Hydroxyprogesterone Caproate (17-OHPC) and Preterm Birth

The study will determine the association between plasma concentrations of 17-OHPC (hydroxyprogesterone caproate) and the rate of preterm birth and will evaluate the impact of several potential covariates on plasma concentrations of 17-OHPC and its efficacy. 17-OHPC (hydroxyprogesterone caproate) administration has proven effective in reducing preterm births in high risk groups but the current dose of 250mg administered intramuscular (IM ) is thought to be an inadequate for a substantial portion of women receiving the therapy. The potential benefit of identifying a therapeutic concentration range and of optimizing the dosage of 17-OHPC are substantial. One cohort of pregnant subjects with a history of a prior spontaneous preterm birth with be randomized to either the 250mg or 500mg weekly intramuscular injections. All subjects will have trough blood samples collected immediately prior to their second injection of the 17-OHPC, at 26-30 weeks (but only after a minimum of 7 injections have been administered) , 6-9 weeks later and at the time of delivery. Another tube of maternal blood will be collected during one of the scheduled blood samples for genotyping. A cord blood specimen will also be collected and with consent, a cord blood specimen will be collected for genetic studies of the infant. Investigators will also collect a small sample of the placenta after delivery. In order to enhance sample size for this trial, investigators will also enroll a second cohort of subjects (ancillary cohort) who are not in the randomized clinical trial (RCT) described above. Women already receiving 250 mg 17-OHPC weekly from their healthcare provider as part of their standard of care will be approached prior to 26 weeks gestation. This will be an observational cohort and subjects enrolled in the ancillary cohort will not be randomized, as they are already receiving the 250 mg dose. Research staff will not administer the study drug to subjects enrolled in the ancillary cohort. These subjects will be asked to provide two blood samples: one at 26-30 weeks and one 6-9 weeks later, which will be utilized to address the primary objective of the study. In response to the addition of the ancillary cohort, randomization for subjects in the RCT will be 2:1 for the 500 mg vs the 250 mg dose. The ancillary study will be implemented initially at the UPITT site only but may be expanded to other sites, as required.