Universal transvaginal cervical length screening during pregnancy increases the diagnostic incidence of low-lying placenta and placenta previa

Abstract

Background: Universal transvaginal cervical length screening has been increasingly implemented with both positive and negative consequences.

Objective: In this study, we described the diagnostic incidence of low-lying placenta and placenta previa with the implementation of universal transvaginal cervical length screening.

Study design: This is a retrospective cohort study of women undergoing midtrimester universal transvaginal cervical length screening. The primary outcome was the rate of transvaginal diagnosis of low-lying placenta or placenta previa using midtrimester universal transvaginal cervical length screening.

Results: This study included 1982 midtrimester ultrasounds, of which 211 indicated a low-lying placenta or placenta previa on either transabdominal or transvaginal ultrasound. With transvaginal ultrasound, a low-lying placenta or placenta previa was diagnosed in 211 women (10.6% of the study population). Of the 211 patients with a low-lying placenta or placenta previa, 90 (42.6%) had a false-negative result, diagnosed using only transvaginal ultrasound; 112 (53.1%) had a true-positive result; and 9 (4.3%) had a false-positive result. The relative risk of having an abnormal finding on ultrasound with the addition of universal transvaginal cervical length screening was 9.2 (95% confidence interval, 4.6-18.1). Of the low-lying placenta or placenta previa diagnosed using midtrimester universal transvaginal cervical length screening, 98.9% resolved (95% confidence interval, 93.7-99.97).

Conclusion: Implementation of universal transvaginal cervical length screening increases the diagnostic incidence of low-lying placenta or placenta previa without an increase in the diagnoses that persist to term, which comes at the cost of increased follow-up ultrasounds and potentially increased anxiety for the patient.

Keywords: cervical length; low-lying placenta; placenta previa; prediction of preterm birth; preterm birth; prevention of preterm birth; transabdominal cervical length; transvaginal cervical length screening; transvaginal ultrasound.