The value of cervical electrical impedance spectroscopy to predict spontaneous preterm delivery in asymptomatic women: the ECCLIPPx prospective cohort study

Objectives

Preterm birth (PTB) accounts for two‐thirds of deaths of structurally normal babies and is associated with colossal lifetime health care costs. Prevention of PTB remains limited by prediction methods of modest accuracy– transvaginal ultrasound (TVUS) cervical length (CL) and quantitative cervicovaginal fetal fibronectin (FFN) estimation. We report the first substantive study detailing the predictive performance of a cervical probe device based on Electrical Impedance Spectroscopy (EIS) for PTB – the EleCtriCaL Impedance Prediction of Preterm birth by spectroscopy of the cervix (ECCLIPPx) studies.

We aimed to compare the accuracy of cervical EIS‐based prediction of spontaneous PTB in asymptomatic women in mid‐trimester to TVUS CL and FFN.

Methods

We studied 449 pregnant women at 20‐22 weeks (V1) and 26‐28 weeks (V2). EIS was performed using the Sheffield Mark 5.0 device that makes measurements in the frequency range 76Hz to 625kHz using a small probe housing tetrapolar electrodes. TVUS CL and FFN were also measured. Associations between cervical EIS, TVUS CL, and FFN and spontaneous delivery < 37 weeks and < 32 weeks were determined by multivariate linear and non‐linear logistic regression analyses. The areas under the Receiver Operator Characteristic (AuROC) curve plots of sensitivity against specificity were used to compare the predictive performance of all parameters, singly and in combination.

Results

Of the 365 asymptomatic women studied at 20‐22 weeks who received no treatments, there were 29 spontaneous PTBs, 14 indicated PTBs, and 322 term births. At the higher frequencies assessed, cervical EIS predicted spontaneous delivery < 37 weeks (AuROC 0.76, 95% CI 0.71‐0.81) compared to TVUS CL (AuROC 0.72, 95% CI 0.66‐0.76) and FFN (AuROC 0.62, 95%CI 0.56‐0.67). Combining all three assessments improved prediction of spontaneous PTB <37 weeks (AuROC 0.80, 95% CI 0.74‐0.83) compared to TVUS CL and FFN alone. Incorporating previous history of PTB into the cervical EIS prediction model improved accuracy of prediction of spontaneous PTB < 37 weeks (AuROC 0.83, 95% CI 0.78‐0.87) and < 32 weeks (AuROC 0.86, 95% CI 0.82‐0.90).

Conclusion

Mid‐trimester cervical EIS assessment predicts spontaneous PTB. Larger confirmatory studies investigating its potential clinical utility and to inform effective preventive interventions are required.