The effect of different dosages of progesterone suppositories on uterine-fetal vascular resistance in women at risk of premature delivery and its comparison with the control group

Despite the widespread use of progesterone in pregnancy, there is limited information on its effect on uterine-placental blood circulation and especially on the fetal blood circulation system in the second half of pregnancy. The present study was conducted with aim to investigate the effect of different dosages of progesterone suppositories on Doppler ultrasound indices of uterine, umbilical, and middle cerebral arteries of the fetus and the incidence of preterm delivery in women at risk of premature delivery.

This double-blind randomized clinical trial study was performed in 2018-2020 on 90 pregnant women with gestational age of 24-33 weeks and diagnosis of preterm labor. The subjects were randomly divided into three groups. All three groups underwent Doppler ultrasound of uterine, umbilical, and middle cerebral arteries of the fetus at admission. Then, in the first group progesterone 400 mg and in the second group progesterone 200 mg were prescribed vaginally and the third group was studied as a control group. All the three groups underwent Doppler ultrasound again 48 hours later. Vascular resistance was measured based on RI (resistance index) and PI (pulsatility index) Doppler parameters. Data analysis was done using SPSS statistical software (version 16) and one-way analysis of variance, Kruskal-Wallis, Chi-square, Fisher's exact, paired t-test, Wilcoxon, Man-Whitney, and logistic regression tests. P<0.05 was considered statistically significant.

There were no significant differences among the three groups in terms of maternal age, parity, gestational age, cervical length, history of preterm delivery, RI and PI of the uterine, umbilical, and middle cerebral arteries of the fetus at admission (P>0.05). In both progesterone groups, RI and PI significantly decreased in all three fetal uterine, umbilical, and middle cerebral arteries (P<0.05) in 48 hours after the intervention compared to the beginning of hospitalization. The reduction of PI and RI indexes of all arteries except PI of uterine artery (P=0.105) was significant in 48 hours after intervention in progesterone groups compared to the control group (P<0.05).

The administration of a single dose of 200 or 400 mg of vaginal progesterone in women with gestational age of 24-33 weeks with diagnosis of preterm labor causes a significant decrease in the resistance of the uterine, umbilical, and fetal vessels after 48 hours.