Objective: To construct the reference range for cervical length (CL) measured by transvaginal ultrasound (TVS) in twin pregnancies at 16- to 34-weeks’ gestation.

Material and Methods: The present study was a retrospective cohort study performed on 123 uncomplicated twin pregnancies delivered at 34-weeks’ gestation or beyond. All twin pregnancy women’s CL at 16- to 34-weeks’ gestation who delivered at Ramathibodi Hospital between February 22, 2016 and March 5, 2019 were examined. The study excluded those who had abortion, history of previous preterm delivery (PTD), monoamniotic twins, single twin demised, history of cervical insufficiency, history of cervical surgery, cervical cerclage, cervical pessary placement, fetal anomaly, fetal chromosome abnormality, fetoscopic surgery or unknown pregnancy outcome. Five hundred seventy-nine CL measurements were analyzed for constructing the mean CL, standard deviation, 95% confidence intervals, and the percentiles of CL.

Results: The mean gestational age (GA) at delivery was 36.7 weeks’ gestation. Forty-two percent of women had spontaneous late PTD. The significant negative correlation between CL and GA was demonstrated (r=–0.549) at p<0.01. The mean CL of 579 measurements was 33.2±9.2 mm, while the mean CL captured at 18 to 24 weeks’ gestation was 38.3±5.8 mm. The reference ranges of CL of each GA were established.

Conclusion: The mean CL at mid-trimester of twin pregnancies was 38.3 mm The reference range for CL in twin pregnancies between 16- and 34-weeks’ gestation was constructed.

Keywords: Cervical length (CL); Transvaginal ultrasound (TVS); Twin pregnancies

DOI: 10.35755/jmedassocthai.2022.04.13297

Received 14 October 2021 | Revised 21 March 2022 | Accepted 31 March 2022