the effect of vaginal progesterone in reducing preterm birth in women with an increased uterocervical angle: a randomized controlled trial

Background :preterm birth (ptb) is a leading cause of perinatal mortality. identifying women at high risk of ptb and implementing effective prevention strategies are essential for improving neonatal outcomes. objectives :the present study aimed to evaluate the effectiveness of vaginal progesterone in reducing ptb among pregnant women with an increased uterocervical angle (uca). methods :in this randomized clinical trial conducted at imam-khomeini hospital complex, tehran, iran, from january to december 2024, fifty-two pregnant women between 18 and 20 weeks of gestation with cervical length (cl) ≥ 30 mm and a uca > 105° were enrolled. participants were randomly assigned to an intervention or control group using a simple randomization method. the intervention group received 400 mg of vaginal progesterone suppositories daily from 18 - 20 weeks until 36 weeks of gestation, while the control group received no progesterone. statistical analyses included descriptive statistics, independent t-test, chi-square or fisher's exact test, and regression analysis. results :the intervention group had a significantly higher mean gestational age at delivery (269.7 ± 8.6 days) compared to the control group (262.0 ± 15.4 days; p = 0.031). the incidence of ptb was significantly lower in the intervention group (7.7%) versus the control group (34.6%; p = 0.038). regression analysis indicated that progesterone administration was associated with a significantly reduced risk of ptb (or 0.14, 95% ci 0.02 - 0.79, p = 0.026). conclusions :vaginal progesterone may serve as an effective prophylactic intervention to reduce ptb in women with a normal cl but increased uca. it is a safe, accessible, and affordable strategy for ptb prevention in this subgroup.