Comparison of intramuscular progesterone with oral nifedipine for treating threatened preterm labor: A randomized controlled trial.

Threatened preterm labor (TPL) is the leading cause of hospitalization during pregnancy. Tocolytic agents are the primary therapeutic options for TPL. The aim of this study is to compare intramuscular progesterone with oral nifedipine as a tocolytic agent. This randomized controlled trial was carried out in a teaching hospital (Shahid Akbarabadi) in Tehran, Iran, from December 2011 to November 2012. Three hundred and fifteen singleton pregnant women aged >18 yrs at 26-34 weeks' gestation with the diagnosis of threatened preterm labor (TPL) were randomly received either intramuscular progesterone or oral nifedipine for tocolysis. Maternal and neonatal outcomes were then compared between the two interventions. P value less than 0.05 was considered statistically significant. IRCT registration number of this study is IRCT201112198469N1 The success rate of progesterone and nifedipine in treating TPL were 83% and 82.7%, respectively. There was no significant difference between the two interventions with regard to gestational age at delivery, type of delivery, the time interval until the delivery, birth weight, NICU admission rate and hospital stays. Progesterone administration was associated with lower duration of NICU stay as compared with nifedipine (0.33±0.77 days vs.1.5±3.2 days, p<0.05). None of the two drugs caused any major side effects. Single dose intramuscular progesterone is as effective as oral nifedipine in treating TPL. It also significantly reduces the NICU stay.