Clinical Correlates of Placenta Accreta Spectrum Disorder Depending on the Presence or Absence of Placenta Previa: A Systematic Review and Meta-analysis

Objective: To evaluate whether there are differences in risk factors and maternal outcomes of pregnancies complicated by placenta accreta spectrum depending on the presence or absence of placenta previa.

Data sources: We performed a systematic search in Medline, EMBASE, ClinicalTrials.gov , and Web of Science from inception through April 25, 2022, without language or date restrictions. Search strategy included the key words "placenta accreta," "placenta increta," "placenta percreta," "adherent placenta," "invasive placenta," "abnormal placent*," "placenta previa," and "marginal placent*."

Methods of study selection: Of the 1,122 articles screened, seven studies were included in the final review. Studies were included if they compared the risk factors and maternal outcomes of pregnancies complicated by placenta accreta spectrum depending on the presence or absence of placenta previa.

Tabulation, integration, and results: A random-effects model was used to pool the mean differences or odds ratios (OR) and the corresponding 95% CIs using RevMan software. A total of 3,342 pregnancies complicated by placenta accreta spectrum were included in the meta-analysis (2,365 without previa and 977 with previa). Pregnancies complicated by placenta accreta spectrum without previa were more likely to have been conceived by in vitro fertilization (IVF) (OR 3.11, 95% CI 1.93-5.02, P <.001, I 2 =52.0%) and to be associated with prior dilation and curettage (D&C) (OR 1.60, 95% CI 1.15-2.22, P =.005, I 2 =0.0%) and myomectomy (OR 2.47, 95% CI 1.31-4.66, P =.005, I 2 =0.0%), but they were less likely to be associated with prior cesarean delivery (OR 0.15, 95% CI 0.06-0.37, P <.001, I 2 =87.0%). Placenta accreta spectrum without previa was less likely to be diagnosed antenatally (OR 0.07, 95% CI 0.04-0.11, P <.001, I 2 =38.0%). Also, women with pregnancies without previa had lower rates of red blood cell transfusion, intensive care unit admission, risk of hysterectomy, unscheduled delivery, and intraoperative bowel or bladder injuries.

Conclusion: Pregnancies complicated by placenta accreta spectrum without previa had a more prominent association with IVF and prior D&C and myomectomy but were much less likely to be associated with prior cesarean delivery. Further, placenta accreta spectrum without previa was less likely to be diagnosed antenatally, although it had better maternal outcomes as compared with placenta accreta spectrum with previa.

Systematic review registration: PROSPERO, CRD42022307637.