2Tort J, Rozenberg P, Traore M, et al. Factors associated with postpartum hemorrhage maternal death in referral hos pitals in Senegal and Mali~ a cross sectional epidemiological survey[J]. BMC Pregnancy Childbirth, 2015, 3(15)~ 235.
3Yeniel AO, Ergenoglu AM, ltil IM, et al. Effect of placenta previa on fetal growth restriction and stillbirth [J]. Arch Gyneco! Obstet, 2012, 286(2): 295 298.