Transvaginal cervical length and amniotic fluid index: can it predict delivery latency following preterm premature rupture of membranes?

Abstract

Objective: We sought to determine whether transvaginal cervical length (TVCL), amniotic fluid index (AFI), or a combination of both can predict delivery latency within 7 days in women presenting with preterm premature rupture of membranes (PPROM).

Study design: This was a prospective observational study of TVCL measurements in 106 singleton pregnancies with PPROM between 23-33 weeks. Delivery latency was defined as the period (in days) from the initial TVCL after PPROM to delivery of the infant, with our primary outcome being delivery within 7 days of TVCL. The independent predictability of significant characteristics for delivery within 7 days was determined using multiple logistic regression. Sensitivity, specificity, and predictive values were used to examine whether the presence of a short TVCL, AFI, or a combination of both affected the risk of delivery within 7 days.

Results: Delivery within 7 days occurred in 51/106 (48%) of pregnancies. Median duration (interquartile range) from PPROM to delivery and TVCL to delivery was 8 days (4.0-16.0) and 8 days (3.0-15.0), respectively. Using multiple regression TVCL as a continuous variable (odds ratio, 0.65; 95% confidence interval, 0.44-0.97; P < .05), AFI ≤5 cm (odds ratio, 4.69; 95% confidence interval, 1.58-13.93; P < .01) were determined to be independent predictors of delivery within 7 days. In all, 42 women (40%) had a TVCL ≤2 cm, while 62 (59%) had AFI ≤5 cm. A total of 26 women (25%) had a combination of both TVCL ≤2 cm and AFI ≤5 cm, while 28 women (27%) had neither characteristic. The predictive value of delivery within 7 days for a TVCL ≤2 cm was 62%, and for an AFI ≤5 cm was 58%. Having a combination of low TVCL and low AFI did not increase the predictive value of delivery within 7 days (58%). In contrast, only 3 of 27 women (11%) with neither characteristic delivered within 7 days. The predictive value of delivery >7 days for TVCL >2 cm alone was 61%. This predictive value changed when analyzed in conjunction with an AFI ≤5 cm and >5 cm at 42% and 89%, respectively.

Conclusion: A shorter TVCL and an AFI ≤5 cm independently predict delivery within 7 days in women presenting with PPROM. The combination of an AFI >5 cm and TVCL >2 cm greatly improved the potential to remain undelivered at 7 days following cervical length assessment. These findings may be helpful for counseling and optimizing maternal and neonatal care in women with PPROM.

Keywords: amniotic fluid index; cervical length; labor latency; preterm birth; preterm premature rupture of membranes.