Vaginal versus intramuscular progesterone in the prevention of preterm labor and their effect on uterine and fetal blood flow

Objectives: To compare vaginal with intramuscular progesterone administration to prevent preterm labor and to detect the effect of both on the uterine and fetal circulations. Study design: Prospective comparative clinical trial. Population: Eighty three pregnant women at 20–24 weeks gestation at risk of preterm labor were classified into: Thirty six women who received micronized progesterone tablets 200 mg vaginally daily (Group 1), 28 women who received 17 alpha hydroxyl progesterone caproate 250 mg intramuscular once weekly (Group 2), and 19 women who had not received any progesterone and settled as control group. Methods: Doppler examination of fetal middle cerebral artery, umbilical artery and uterine artery was done before and one week after progesterone administration, progesterone was continued till 36 weeks pregnancy or delivery. Main outcome measures: Incidence of preterm delivery, mean gestational age and birth weight at delivery, the need for neonatal intensive care unit admission and neonatal mortality. Doppler indices before and after progesterone administration was also measured and compared in both groups. Results: The incidence of preterm delivery in Group 1 and Group 2 was significantly lower than in the control group (25%, 21.4% and 52%, respectively). A significant decrease in fetal MCA-PI and RI was noted after progesterone administration both vaginally and I.M. But a significant decrease in the mean uterine artery RI and PI was noted only after progesterone was administrated vaginally. Conclusion: Vaginally administrated progesterone was nearly as equally effective as intra muscular progesterone in the prevention of PTL in women at risk and both were associated with significant reduction in fetal MCA-PI and RI, but a significant reduction in uterine artery RI and PI was observed only after vaginal progesterone