Serum Levels of Hormones Known to Affect Parturition in Patients Receiving 17 Alpha-Hydroxyprogesterone Caproate (17-P) for the Prevention of Preterm Delivery

A recent study by Meis and colleagues published in the New England Journal of Medicine in June 2003 demonstrated a 33% reduction in the rate of preterm delivery in patients with a previous history of preterm delivery who then used weekly 17-P injections in the subsequent pregnancy.

This is a milestone in the prevention of preterm delivery and is the reason you have chosen to receive treatment with 17-P.

However, how 17-P works to prevent preterm delivery is unclear. Knowledge of the mechanism of action of 17-P would help in selecting patients for treatment and may be useful in monitoring the efficacy of therapy.

Studies have suggested that the timing of delivery depends on a type of placental clock, affected by levels of corticotropin-releasing hormone (CRH) and progesterone (P).

CRH can be thought to act as an accelerator, and P as a brake. Serial injections of 17-P beginning in the second trimester of pregnancy may prevent preterm delivery by maintaining progesterone dominance, and be reflected in increased levels of progesterone and/or 17-P, or decreased levels of cortisol and/or CRH. These are the hormones that will be measured in this study.