6Lum biganon P, Laopa iboon M, Gulmezoglu AM et al. Method of de- livery and pregnancy outcomes in Asia: the WHO global survey on ma- ternal and perinatal health 2007 -08 [ J) . The Lancet, 2010, 375 (9713) : 490.
7Sentilhes L, Goffinet F, Talbot A et al. Attempted vaginal versus planned cesarean delivery in 195 breech first twin pregnancies [J]. Acta Obstet Gynecol Scand, 2007, 86 (1) : 55.