Abstract
Objective: To determine if there is an association between uterocervical angle (UCA) and spontaneous preterm birth (sPTB) < 37 weeks for women with twins.
Materials and methods: Retrospective cohort study from 2014 to 2017 of twin pregnancies with cervical length (CL) screening between 15 0/7 and 24 6/7 weeks. Monochorionic-monoamniotic twins were excluded. Post-hoc UCA measurements were analyzed as a continuous variable and a wide UCA was also defined as an angle >95° and >110°. The primary outcome was sPTB < 37 weeks. Secondary outcomes were sPTB <34 weeks, <32 weeks, CL, and performance metrics for UCA. Binary logistic regression controlled for age, tobacco use, prior sPTB, CL, and gestational age at CL measurement.
Results: A total of 114 women were studied. The rate of sPTB <37 weeks was 35.0%, <34 weeks was 21.4%, and <32 weeks was 17.1%. As a continuous variable, mean UCA was 117.9° (SD 27.1°) for delivery ≥37 weeks and 133.1° (SD 23.1°) <37 weeks (p = .002). A wider mean UCA was also associated with sPTB <34 weeks (sPTB ≥34 weeks: 120.9° [SD 26.5°] vs. <34 weeks: 133.0° [SD 22.8°], p = .025) and sPTB <32 weeks (sPTB ≥32 weeks: 121.2° [SD 25.9°] vs. <32 weeks: 135.0° [SD 24.0°], p = .018). However, after controlling for age, prior sPTB, tobacco use, CL measurement, and gestational age at CL measurement, UCA was not associated with sPTB <37 weeks, <34 weeks, or <32 weeks. UCA >110° was associated with sPTB <37 weeks after controlling for confounders (aOR 3.6 [95% CI 1.2–10.5], p = 0.02). There was no association between UCA >110° and sPTB <34 or <32 weeks. Furthermore, a UCA >95° was not associated with sPTB <37, <34, or <32 weeks. As a screening tool for sPTB <37 weeks, a UCA of >110° had a sensitivity of 85.7%, specificity of 43.1%, positive predictive value of 53.2%, negative predictive value of 80.0%, positive likelihood ratio of 1.5, and negative likelihood ratio of 0.3.
Conclusions: In a cohort of dichorionic-diamniotic and monochroionic-diamniotic twins, UCA >110° was associated with sPTB <37 weeks. However, second trimester UCA had a low positive likelihood ratio and was not a robust marker for the prediction of sPTB in twins.
Acknowledgments
Dr. Dongmei Li for assistance with statistical analysis.
Disclosure statement
No financial interest or benefit that has arisen from the direct applications of this research.