Background: For women with a history of prior cesarean deliveries who are diagnosed with placenta previa, the risk of placenta previa accreta significantly increases, making this group the highest risk category for this obstetric complication.
Objective: This study aimed to evaluate the diagnostic accuracy of prenatal ultrasound imaging in identifying placenta accreta. Furthermore, it investigated how the depth of villous invasion impacts the clinical management of women with placenta previa or low-lying placenta and a history of one or more prior cesarean deliveries. Effective Delivery Diagnosis is crucial in these high-risk pregnancies.
Study Design and Data Sources: A comprehensive search was conducted across PubMed, Google Scholar, clinicalTrials.gov, and MEDLINE to identify relevant studies published between 1982 and November 2016.
Study Eligibility Criteria: The inclusion criteria focused on cohort studies providing data on previous delivery methods, placenta previa or low-lying placenta diagnosed via prenatal ultrasound, and pregnancy outcomes. From an initial pool of 171 records, 14 cohort studies (5 retrospective and 9 prospective) met the eligibility criteria for quantitative analysis.
Study Appraisal and Synthesis Methods: The methodological quality of the selected studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool, ensuring a robust evaluation of delivery diagnosis methods.
Results: The 14 cohort studies encompassed 3889 pregnancies with placenta previa or low-lying placenta and at least one prior cesarean delivery, all screened for placenta accreta. Placenta previa accreta was diagnosed in 328 cases (8.4%), with prenatal ultrasound successfully identifying 298 of these cases (90.9%). The incidence of placenta previa accreta varied with the number of prior cesareans: 4.1% in women with one prior cesarean and 13.3% in those with two or more.
Ultrasound’s performance in antenatal detection of placenta previa accreta, a critical aspect of delivery diagnosis, was found to be more effective in prospective studies compared to retrospective ones. Prospective studies showed a diagnostic odds ratio of 228.5 (95% confidence interval, 67.2-776.9), while retrospective studies had a ratio of 80.8 (95% confidence interval, 13.0-501.4). However, only two studies provided detailed information on the correlation between villous invasion depth and the number of previous cesarean deliveries, independent of invasion depth. In cases with available management data, cesarean hysterectomy was performed in 208 out of 232 cases (89.7%).
Larger prospective studies indicated positive correlations between the cumulative rates of more invasive accreta placentation and ultrasound’s sensitivity and specificity. However, this correlation was not observed with diagnostic odds ratio values. Notably, the study found a lack of data regarding ultrasound screening for placenta accreta during routine midtrimester scans in non-expert ultrasound facilities, highlighting a gap in standard delivery diagnosis protocols.
Conclusion: Accurate prenatal evaluation of accreta placentation risk is essential for planning individualized delivery management in women with low-lying placenta/previa and a history of cesarean delivery. Ultrasound demonstrates high sensitivity and specificity in the prenatal delivery diagnosis of accreta placentation, particularly when performed by experienced operators. The development and implementation of a standardized prenatal screening protocol are now crucial to improve outcomes for this increasingly prevalent and serious obstetric complication, ensuring timely and effective delivery diagnosis and management.
