ResultsCharacteristic resultsOur search yielded 1148 publications of which 11 studies including 14 unique PPH prevalence rates, met inclusion criteria (Fig 1). Five took place in North America [28–32], three in Asia [6, 33, 34], two in Europe [35, 36], and one in Australia [37] (Table 1). The articles were published between 2000 and 2016, and the final sample comprised 5146 unique pregnant women with placenta previa. Sample sizes ranged from 95 to 1612 participants with a mean sample size of 488. Mean age was 31.89 years (range = 29.78–34.20 years), and mean gestation age was 37.77 weeks (35.40–39.40). Five studies [28, 29, 34–36] reported anterior placenta frequencies and 36.05% of women (n = 860) were anterior placenta. 29.67% of women were prior cesarean delivery (n = 954), 67.73% of women were multiparae (n = 3322) and 6.85% of women were accompanied with placenta accrate. Six studies [28, 29, 31, 33–35] (n = 1329) including women were diagnosed with low-lying placenta previa. The prevalence of PPH ranged from 3.6% [31] to 58.7% [30]. When evaluated by STROBE quality assessment criteria, two studies [33, 37] received 9 points, five [29–31, 34, 35] received 8 points, and four [6, 28, 32, 36] received 7 points (S2 Table). The quality scores showed that studies were acceptable quality.