The present umbrella review evaluated the environmental risk factors prior to conception associated with placenta accrete spectrum(PAS) based on meta-analyses and systematic reviews.

We searched PubMed, Scopus, and Web of Science until October 14, 2021. All meta-analyses that had focused on assessing the risk factors associated with the PAS were included. We calculated summary effect estimates, 95% CI, heterogeneity I², 95% prediction interval, small-study effects, excess significance biases, and sensitive analysis. The quality of the meta-analyses was evaluated with A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR 2).

The risk factor of in-vitro fertilization (IVF) (OR 5.03, 95% CI: 3.34, 7.56) was graded as suggestive evidence (class III). The multiple gestation (OR 1.90, 95% CI: 1.26, 2.88) was graded as the risk factor with weak evidence (class IV). Hypertension disorders (OR 0.5, 95% CI: 0.30, 0.82), low socioeconomic status (SES) (OR 0.51, 95% CI: 0.37, 0.71) (class IV) and male fetus (OR 0.79, 95% CI: 0.74, 0.84) (class III) were as the protective factors (class IV). The methodological quality of four of the included meta-analyses, based on AMSTAR 2, was low and three meta-analyses were critically low.

The multifetal gestation and IVF were environmental risk factors for the PAS, while hypertension disorders, low SES, and male fetus were the protective factors.