Ultrasonographic cervical length assessment in pregnancies with placenta previa and risk of perinatal adverse outcomes: a systematic review and meta-analysis.

OBJECTIVE

This study aimed to examine the association between cervical length and the risk of adverse outcomes in placenta previa pregnancies. In addition, the diagnostic accuracy of cervical length in predicting emergency cesarean delivery due to hemorrhage was evaluated.

DATA SOURCES: PubMed, Web of Science, and Embase were systematically searched up to January 21, 2023.

STUDY ELIGIBILITY CRITERIA: Observational studies investigating the relationship between cervical length and maternal adverse outcomes in patients with placenta previa were considered eligible. The primary outcome was the diagnostic accuracy of cervical length measured at 28 to 34 weeks of gestation for the prediction of emergency cesarean delivery due to hemorrhage. The secondary outcomes were the probability of antenatal bleeding, preterm birth (both iatrogenic and spontaneous), and postpartum hemorrhage >2000 mL. Insufficient data were available on the transfusion procedure in cases where the cervical length was <30 mm.

METHODS

For prognostic analysis, the random-effects model was used to pool the odds ratios and the corresponding 95% confidence intervals. For the diagnostic part, we used a summary receiver-operating characteristic curve, pooled sensitivities and specificities, area under the curve, and summary likelihood ratios.

RESULTS

A total of 13 studies presenting data on 1462 pregnancies with placenta previa were included. Cervical length ≤30 mm at 28 to 34 weeks of gestation had a sensitivity of 61% (95% confidence interval, 43-77), specificity of 83% (95% confidence interval, 76-88), and area under the curve of 0.83 (95% confidence interval, 0.80-0.86) for the prediction of emergency cesarean delivery. Furthermore, cervical length ≤30 mm was associated with antenatal bleeding (odds ratio, 3.62; 95% confidence interval, 2.09-6.26; P<.001; I2=54.8%), preterm birth (odds ratio, 8.46; 95% confidence interval, 3.05-23.44; P<.001; I2=83.6%), and postpartum hemorrhage (odds ratio, 6.89; 95% confidence interval, 4.51-10.53; P<.001; I2=0.00%).

CONCLUSION

Short cervical length (≤30 mm) measured at 28 to 34 weeks of gestation can assist in predicting the risk of emergency cesarean delivery due to hemorrhage in pregnancies with placenta previa. Furthermore, short cervical length is significantly associated with the risk of antenatal bleeding, preterm birth, and postpartum hemorrhage in pregnancies with placenta previa.