Fatemeh Mirzaei - Associate Professor, Department of Obstetrics and Gynecology, Faculty of Medicine and Physiology Research Center, Institute of Basic and Clinical Physiology Sciences, Kerman University of Medical Sciences, Kerman, Iran
samira azimi - Resident, Department of Obstetrics and Gynecology, Student Research Committee, Kerman University of Medical Sciences, Kerman, Iran
Ghazal Mansouri - Associate Professor, Department of Obstetrics and Gynecology, Faculty of Medicine, Kerman University of Medical Sciences, Kerman, Iran

Background: Women with preterm labor put in an arrest phase by tocolytic therapy, are at increased risk of recurrent preterm labor. The aim of this study is to evaluate vaginal progesterone suppositories as compared to intramuscular type in order to prevent preterm labor in women with episodes of threatened preterm labor. Methods: This prospective longitudinal study was conducted on ۱۰۸ pregnant women who were presented with symptoms of threatened preterm labor and went on tocolytic therapy in order to prevent uterine activity. Their gestational age (GA) ranged between ۲۴-۳۴ complete weeks and mothers were at risk of preterm delivery. After acute phase control and delivery supression, ۴۰۰mg of prophylactic vaginal suppository was prescribed each day in the first intervention group and ۲۵۰ mg of intra-muscular ۱۷-alpha hydroxyprogesterone caproate was injected once a week in the second intervention group. Treatment continued in both groups up to ۳۶ weeks of gestational age or until delivery. Results: The prevalence of preterm delivery was significantly higher in patients receiving intra-muscular progesterone (۵۵.۶% vs. ۳۷%) (P = ۰.۰۵). Moreover, the birth weight in the intramuscular progesterone group was significantly lower than the other group (۲۶۸۵.۱۸ g vs. ۲۹۹۹.۲۵ g) (P = ۰/۰۲). First and fifth minute Apgar score were also significantly lower in this group than the vaginal progesterone suppository group (p <۰.۰۵).). There was no statistical significance observed comparing the latent phase duration in the two groups. (۴۶.۹ days vs. ۴۱.۴۴ days) (P= ۰.۱۶). Conclusion: The results of this study suggest that vaginal progesterone suppository decreases the rate of preterm delivery while it also improves the newborn outcome at a higher rate compared to intra-muscular ۱۷-alpha-hydroxyprogesterone caproate.

Preterm delivery, Vaginal progesterone suppository, ۱۷-alpha hydroxyprogesterone caproate