Abstract: Objective: To investigate the unwanted pregnancy，and its causes，in those postpartum lactation women in one year after cesarean section，so as to develop personalized intervention in practice. Methods: The questionnaire survey was firstly done in those lying-in women during hospitalization after cesarean section by well-trained investigators. The questionnaire survey was done again after 1 year（or when they used effective contraceptives）. Results: 68.3% of women got the contraceptive knowledge from internet in general；61.5% of women restarted sexual activities in 2-3 months after delivery. The optimal chances for those women after childbirth to get contraceptive knowledge were medical guidance during hospitalization，query from internet by themselves, and postpartum follow-up visit by community doctors. There were 3% subjects who had their unwanted pregnancies in one year after delivery. In those women with unwanted pregnancies，51.7% women did not know the available methods of emergency contraception，72.4% women didn′t know the right time of emergency contraception，and 41.4% women did not understand the dangerousness of re-pregnancy during lactation and abortion in one years after delivery. Conclusions: The important way to guide the maternal contraception is to set some columns in the governmental websites of maternal and child health care，or/and to develop professional mechanism of online consulting.

Key words: Cesarean section, Pregnancy, unplanned, Pregnancy rate, Questionnaires