Abstract： Objective To discuss the diagnosis,treatment and following-up of cervical intraepithelial neoplasia (CIN) during pregnancy.Methods Eighteen pregnant women with CIN,presented to the hospital from Jan.2004 to May.2008,were retrospectively reviewed.Pap smear,HPV,copolscopy and cervical biopsy were performed for diagnosis and all were followed up by Pap smear and copolscopy during pregnancy every 12 weeks,while 15 were followed up until 6-8 weeks postpartum.Results The incidence of CIN during pregnancy was 0.16%.All of the 18 women had abnormal Pap smear,followed by colopscopy and biopsy.Conservative management during the pregnancies every 3 months showed no progress in CIN.Among the 18 cases,17 delivered at term and only 1 preterm (36+4 weeks).Two out of the 18 women had normal delivery (11.1%),2 by forceps(11.1 %) and 14 by cesarean sections (77.8%).No neonatal apnea or neonatal respiratory distress syndrome had been observed.Pathological diagnosis was confirmed in all cases prenatally,including 4 CIN1,4 CIN2 and 10 CIN3.Four out of the 10 CIN3 remained after delivery,while 1 changed to CIN2.These 5 cases underwent leep electrical excision procedure and Pap smear results turned to normal at 6 to 11 months after delivery.One HSIL case were lost.The rest 4 CIN3 and all of the 8 CIN1 and CIN2 cases turned to normal or lesser degree.Fourteen of the 18 women received HPV test during pregnancy,and 12 (85.7%) were positive,among which 7 women were followed up at postpartum and 6 of them were HPV positive.Conclusions The three steps method for diagnosis of CIN during pregnancy is safe and effective.Conservative management of CIN during pregnancy is recommended.