Distribution of uterocervical angles in the second trimester of pregnant women at low risk for preterm delivery

Abstract

The uterocervical angle (UCA) has recently been studied as a parameter to identify women at risk for spontaneous preterm birth (sPTB). This study aimed to investigate the distribution of UCA values by transvaginal sonography (TVS) in the second trimester of women at low risk for sPTB. TVS was performed in 450 low-risk pregnant women at gestational age (GA) 16^0/7–24^0/7weeks. The UCA distribution by GA was visualised using a scatter plot. The range of UCA values and their relationship with GA were assessed using quantile regression analysis. p < .05 was considered statistically significant. A total of 242 participants with anteflexed uterus, no history of caesarean section and term delivery were analysed. The normal range of UCA (5th and 95th percentiles) was from 63.0 degrees (95% CI, 53.1–72.9) to 148.8 degrees (95% CI, 139.5–158.0) with no significant changes during this GA period (–0.3 degrees per week, p = .757).

Impact statement

• What is already known on this subject? Spontaneous preterm birth (sPTB) is a major problem in obstetrics. A screening strategy using history of sPTB and cervical length (CL) measurement is the current standard to identify women at risk for sPTB and provide adequate prevention. However, a third of women who are identified as low risk go on to have sPTB, so a better means needs to be found to more reliably identify women at risk. Various studies have found that a wide uterocervical angle (UCA) was associated with sPTB, and thus the UCA has been proposed as a potential sPTB screening parameter. However, to date there is a lack of prospective studies evaluating this proposal, and no consensus about the proper gestational age to perform UCA measurements to identify women at risk of sPTB.

• What do the results of this study add? This study reports the distribution of UCA at the GA of 16^0/7–24^0/7 weeks of low-risk singleton pregnancy women who delivered at term. The mid-90% values ranged from 63.0 degrees to 148.8 degrees with no significant differences in this GA period.

• What are the implications of these findings for clinical practice and/or further research? Because of the wide range of UCA values at GA 16^0/7–24^0/7 weeks, more studies regarding UCA values in various gestational ages are required to fully understand the trend of UCA values along pregnancy and confirm whether or not the UCA would be a useful parameter for sPTB prediction and if so at what gestational age it would have to be assessed.

Keywords:

• Uterocervical angle
• second trimester
• low risk
• preterm birth
• transvaginal ultrasonography

Acknowledgments

The authors thank Dr. Chitkasem Suwanrath and Ms. Nannapat Kaewmanee of the Maternal and Foetal Medicine Unit, Department of Obstetrics and Gynaecology, Faculty of Medicine, Prince of Songkla University, and Ms. Walailuk Jitpiboon of the Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, for their useful research suggestions, assistance in patient enrolment and data analysis, respectively.

Disclosure statement

The authors report no conflicts of interest.

Additional information

Funding

Funding for the study from the Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand, is gratefully acknowledged.