3Ginsburg ES, Frates MC, Rein MS, et al. Early diagnosis and treatment of cervical pretgnancy in an invitro fertifization program[J]. Fertil Steril, 1994,61 (5) :966 - 969.
4Boyko TR, O' brien .IF. Cervical pregrumcy: a case report[J]. Ann Emerg Med,2001,38(2) : 177 - 180.