Use of uterine electromyography in the prediction of preterm birth after transvaginal cervical cerclage

Background: Preterm birth (PTB), complications of which account for approximately 35% of deaths among neonates, remains a crucial issue. Cervical insufficiency (CI) is defined as the inability of the utrine cervix to retain a pregnancy, leading to PTB. Cervical cerclage is an efficient surgery for CI patients by preventing the cervix from being further mechanically shortened. Unfortunately, a certain number of patients who had cerclage still delivered prematurely, raising the urgent need to accurately assess the risk of PTB in patients with cerclage. Uterine electromyography (uEMG) is an emerging technology that characterizes uterine contractions by describing the actual evolution process of uterine activity and has been used to predict PTB in recent years.

Method: In this single-center retrospective case-control study, singleton pregnancy women who received cervical cerclage and uEMG assessment between January 2018 and January 2022 at the Sun Yat-sen Memorial Hospital of Sun Yat-sen University were enrolled.

Results: 32 PTBs were observed of the 69 women who underwent assessment. Based on multivariate logistic regression analysis, PTB after cerclage was significantly associated with previous PTB history or mid-trimester pregnancy loss (OR: 2.87, 95%CI: 1.49-5.54) and contraction frequency detected by uEMG (OR: 2.24, 95%CI: 1.44-3.49). The AUC of contraction frequency (0.766, P<0.001) was observed, and the optimal cut-off value suggested by Youden Index was 1.75 times per hour. Combined with previous preterm history and cervical length, the AUC of contraction frequency reached 0.858. After stratification by contraction frequency, the median duration was 11 weeks in the high frequency group (> 1.75 times per hour) and 15 weeks in the low frequency group (≤ 1.75 times per hour) (P<0.001).

Conclusions: The uEMG effectively predicts PTB after transvaginal cervical cerclage and provides a new method for clinicians to evaluate the pregnancy outcome of CI patients.