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

Objective This study was undertaken to examine the association between CL and the risk of adverse outcomes in placenta previa pregnancies. Additionally, the diagnostic accuracy of CL in predicting emergency cesarean delivery (CD) 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 CL and maternal adverse outcomes in patients with placenta previa were considered eligible. The primary outcome was the diagnostic accuracy of CL measured at 28 to 34 weeks of gestation for the prediction of emergency cesarean delivery (CD) due to hemorrhage. The secondary outcomes were the probability of antenatal bleeding, preterm birth (PTB) both iatrogenic and spontaneous, and postpartum hemorrhage (PPH) above 2000 ml. Insufficient data was available on the transfusion procedure in cases where the cervical length was less than 30 mm. Study appraisal and synthesis methods For prognostic analysis, the random-effects model was used to pool the odds ratios (ORs) and the corresponding 95% confidence intervals (CIs). For the diagnostic part, we used summary receiver–operating characteristics (sROC) curve, pooled sensitivities and specificities, area under the curve (AUC), and summary likelihood ratios (LRs) were calculated. Results A total of 13 studies presenting data on 1,462 pregnancies with placenta previa were included. CL of ≤30 mm at 28 to 34 weeks of gestation had a sensitivity of 61% (95% CI, 43–77%), specificity of 83% (95% CI, 76–88%) and an AUC of 0.83 (95% CI, 0.80–0.86) for the prediction of emergency CD. Furthermore, CL of ≤30 mm was associated with antenatal bleeding (OR 3.62, 95% CI 2.09-6.26, P < 0.001, I2 54.8%), PTB (OR 8.46, 95% CI 3.05-23.44, P<0.001, I2 83.6%), and PPH (OR 6.89, 95% CI 4.51-10.53, P<0.001, I2 0.00%). Conclusion Short CL (≤30 mm) measured at 28 to 34 weeks of gestation can assist in predicting the risk of emergency CD due to hemorrhage in pregnancies with placenta previa. Furthermore, short CL is significantly associated with the risk of antenatal bleeding, PTB and PPH in pregnancies with placenta previa.