3Faiz AS,Ananth CV.Etiology and risk factors for placenta previa:an overview and meta analysis of observational studies.J Matern Fetal Neonatal Med,2003,13:175-190.
4Abu-Heija A,El Jallad F,Ziadeh S.Placenta previa:effect of age,gravidity,parity and previous caesarean section.Gynecol Obstet Invest,1999,47:6-8.
5Hendricks MS,Chow YH,Bhagavath B,et al.Previous cesarean section and abortion as risk factors for developing pla centa previa.J Obstet Gynecol Res,1999,25:137-142.
6Ananth CV,Demissie K,Smulian JC,et al.Relationship among placenta previa,fetal growth restriction and preterm delivery:a population-based study.Obstet Gynecol,2001,98:299-306.
7Demissie K,Breckenridge MB,Joseph L,et al.Placenta previa:preponderance of male sex at birth.Am J Epidemiol,1999,149:824-830.