Prevention of preterm birth among singleton pregnant women with an obtuse uterocervical angle: a quasi-experimental study on the value of cervical pessary combined with progesterone

Abstract Background: Micronized progesterone has been shown to be an effective preterm birth prophylactic intervention in singleton pregnancies with short cervical length measured via transvaginal ultrasound in the second trimester. The use of cervical pessary as a preventive method for preterm birth has limited research and controversial findings when compared to progesterone-combining pessary, with the hypothesis that it narrows the uterocervical angle and reduces the risk of preterm birth. This study aimed to evaluate the value of cervical pessary combined with progesterone in the prevention of preterm birth among singleton pregnant women with a short cervix having uterocervical angles ≥95o. Methods: A quasi-experimental study with a nonequivalent-group design was conducted on 225 singleton pregnant women with a gestational age of 16+0 - 23+6 weeks, having cervical length ≤25 mm. Participants were assigned into two groups: prophylactic treatment with progesterone alone or progesterone combined with a cervical pessary. The association between cervical length, uterocervical angle (≥95o or ≥105o), and preterm birth outcomes (<37 weeks or <34 weeks) was assessed by using a multivariable binary regression model. The difference was statistically significant with p <0.05. Results: The probability of preterm birth <37 weeks in the group of pregnant women with a uterocervical angle ≥95o treated by progesterone plus cervical pessary decreased in comparison to the progesterone alone group, with an odds ratio (95% confidence interval) of 0.343 (0.147-0.801). In the group of pregnant women with a uterocervical angle ≥105o, the treatment by a cervical pessary plus progesterone yielded a lower rate of preterm birth <37 weeks and <34 weeks, with an odds ratio (95% confidence interval) of 0.026 (0.005-0.132), and 0.084 (0.021-0.347), respectively. Conclusions: The results of this study suggested that a cervical pessary has an added effect combined with progesterone in preventing preterm birth among singleton pregnant women with obtuse uterocervical angles. The preventive effect is stronger if the uterocervical angle measurement is ≥105o.