Taking progestogens during high-risk pregnancy could reduce preterm birth Taking progestogens - steroid hormones - during pregnancy could reduce the risk of preterm birth in high-risk single baby pregnancies, research has shown. Although these compounds have been in use for some time, results of individual clinical trials investigating their effectiveness in preventing preterm birth have been conflicting, and so further evaluation of the research evidence was needed. University of York researchers led the Evaluating Progestogens for Prevention of Preterm Birth International Collaborative (EPPPIC) project, a systematic review which brought together and re-analysed datasets from 31 clinical trials of progestogens, including more than 11,000 women and 16,000 babies worldwide.