2Werner CL, LO JY, Heffeman T, et al. Loop electrosurgical excision procedure and risk of preterm birth [J] . Obstet Gynecol, 2010, 115 (3) : 605-608.
3Armarnik S, Sheiner E, Piura B, et al. Obstetric outcome following cer- vical conization [J] . A rch Cynecol Obstet, 2011,283 (4) : 765-769.
4Ferenczy A, Choukroun D, Falcone T, et al. The effect of cervical loop electrosurgical excision on subsequent pregnancy outcome: North American experience [J] . Am J Obstet Gynecol, 1995, 172 (4 Pt 1) : 1246-1250.