Cervical insufficiency is a known risk factor for preterm birth and miscarriage. The etiology of cervical insufficiency has not been fully recognized and the association between it and prior cesarean delivery is unknown. We experienced two similar characteristic cases of cervical insufficiency following term cesarean delivery. Interestingly, both cesarean sections were uneventfully performed after the prolonged second stage of labor. Our experience and recent literature strongly support the idea that an unintentional incision into the uterine cervix during a previous cesarean section may cause cervical insufficiency in subsequent pregnancies. It is important for obstetricians to take into account the possible occurrence of cervical insufficiency depending on the circumstances of previous deliveries. Our report highlights the need to alert obstetricians to take more care with their cesarean section technique.