Transperineal ultrasound measurement of cervical length to predict preterm delivery in women with threatened preterm labour

Objective: This study evaluated the predictive value of cervical length as measured by transperineal ultrasound for preterm delivery and the cut-off value in patients with threatened preterm labour.Methods: Medical records of women admitted to Kwong Wah Hospital between 1 January 2019 and 31 December 2021 for threatened preterm labour at a gestational age between 24+0 and 33+6 weeks were reviewed retrospectively.Patient demographics, cervical length as measured by transperineal ultrasound on admission, and delivery outcomes were collected and analysed.Results: Of 60 women admitted for threatened preterm labour, 21 (35.0%)delivered before 37 weeks.Ten (16.7%) women delivered within 7 days of admission.Cervical length as measured by transperineal ultrasound on admission was positively correlated with the admission-to-delivery interval (r=0.61,p<0.001).Using the cut-off value of 2.5 cm to predict delivery within 7 days of admission was the most sensitive (90.0%) and specific (86.0%).In univariate analysis, risk factors for preterm delivery were previous preterm delivery, maternal age, history of antepartum haemorrhage, and cervical length.In multivariate analysis, only cervical length remained significantly associated with preterm delivery. Conclusion:Transperineal ultrasound is a non-invasive alternative to transvaginal ultrasound for measuring cervical length to predict preterm delivery in patients with threatened preterm labour.A cut-off value of 2.5 cm has high sensitivity and specificity.