Pathologically diagnosed placenta accreta spectrum without placenta previa: a systematic review and meta-analysis

Objective: This systematic review and meta-analysis aimed to assess clinical characteristics related to pathologically proven placenta accreta spectrum without placenta previa.

Data sources: A literature search of PubMed, the Cochrane database, and Web of Science was performed from inception to September 7, 2022.

Study eligibility criteria: The primary outcomes were invasive placenta (including increta or percreta), blood loss, hysterectomy, and antenatal diagnosis. In addition, maternal age, assisted reproductive technology, previous cesarean delivery, and previous uterine procedures were investigated as potential risk factors. The inclusion criteria were studies evaluating the clinical presentation of pathologically diagnosed PAS without placenta previa.

Methods: Study screening was conducted after duplicates were identified and removed. The quality of each study and the publication bias were assessed. Forest plots and I² statistics were calculated for each study outcome for each group. The main analysis was a random-effects analysis.

Results: Among 2598 studies that were initially retrieved, 5 were included in the review. With the exception of 1 study, 4 studies were included in the meta-analysis. This meta-analysis showed that placenta accreta spectrum without placenta previa was associated with less risk of invasive placenta (odds ratio, 0.24; 95% confidence interval, 0.16-0.37), blood loss (mean difference, -1.19; 95% confidence interval, -2.09 to -0.28) and hysterectomy (odds ratio, 0.11; 95% confidence interval, 0.02-0.53), and more difficult to diagnose prenatally (odds ratio, 0.13; 95% confidence interval, 0.04-0.45) than placenta accreta spectrum with placenta previa. In addition, assisted reproductive technology and a previous uterine procedure were strong risk factors for placenta accreta spectrum without placenta previa, whhereas previous cesarean delivery was a strong risk factor for placenta accreta spectrum with placenta previa.

Conclusion: The differences in clinical aspects of placenta accreta spectrum with and without placenta previa need to be understood.