【Objective】To provide further evidence of the association between cesarean scar pregnancy（CSP）and placenta increta，and to investigate the risk of expectant management of CSP.【Methods】A retrospective review of 3 women diagnosed with CSP ，who were managed expectantly ，was performed in the Third Affiliated Hospital of SUN Yat- sen University from January 2014 to December 2018. Their clinical characteristics，sonographic manifestation and poor outcomes were analyzed.【Results】These 3 cases of CSP had 1~2 previous lower segment cesarean sections and their clinical symptoms included recurrent hemorrhage，gross hematuria and severe abdominal pain. Among the 3 cases，the gestational age at diagnosis of CSP was 6+2 weeks，7 weeks and 7+4 weeks，respectively；the sonographic CSP type was typeⅠ，type Ⅱ and type Ⅲ，respectively；the gestational age at the first diagnosis of placenta increta was 24+4 weeks，12+2 weeks and 13+1 weeks，respectively；and all 3 cases were diagnosed as placenta percreta by ultrasound at the second trimester. These 3 cases of CSP were terminated at the second trimester without liveborn neonates because of severe hemorrhage ，colt tamponade of bladder and uterine rupture；and all were confirmed as placenta percreta during surgery with the total blood loss of more than 2 500 mL and without maternal death ，and one got a pathological diagnosis of placenta percreta after subtotal hysterectomy. 【Conclusion】 Placenta percreta should be noticed during the expectant management of CSP because of the close association between CSP and placenta increta. Natural history of CSP is usually associated with adverse outcome，and therefore expectant management of CSP should be carefully chosen.