Prematurity is a leading cause of perinatal morbidity and mortality in many countries. Studies of various tocolytic agents have shown mixed results with little effect in improving pregnancy duration and insufficient data to confirm a definite beneficial effect on neonatal morbidity or mortality. Progesterone is known to have an inhibitory effect on uterine contractility and is thought to play a key role in the maintenance of pregnancy until term. Some investigators looked at the use of progestational agents for the treatment of threatened or established preterm labour. We surveyed the literature for studies on this subject with a view to performing a meta-analysis in order to assess the efficacy of progestational agents in the treatment of threatened or established preterm labour.