Charles Lockwood, MD, Professor and Chair, Department of Obstetrics, Gynecology and Reproductive Services, Yale School of Medicine, discusses research initiatives looking at placental abruption and how it triggers prematurity.

Summary:
1. Prematurity can be caused by placental abruption, which releases thrombin into the uterine deciduas which downregulates progesterone receptors.
2. Progesterone receptor withdrawal in humans appears to trigger parturition.

References and Resources:
Doyle LW. Antenatal progesterone to prevent preterm birth. Lancet. 2009 Jun 13;373(9680):2000-2. Review

da Fonseca EB, Bittar RE, Damião R, Zugaib M. Prematurity prevention: the role of progesterone. Curr Opin Obstet Gynecol. 2009 Apr;21(2):142-7.