Effect of early pregnancy on a previous lower segment cesarean section scar.

OBJECTIVE: To summarize the manifestation, diagnosis, and early management of early pregnancy on a previous cesarean section scar. METHOD: Fifteen cases of early pregnancies implanted on previous cesarean section scars were diagnosed and treated in two obstetrical centers. RESULTS: The 15 patients had light, painless vaginal bleeding and their serum beta-subunit human chorionic gonadotropin (beta-HCG) was elevated. The interval between cesarean section and admission ranged from 6 months to 12 years (7.1+/-3.6 years). Doppler and real-time ultrasonic examinations demonstrated an enlargement of the previous cesarean section scar in the lower segment, a gestational sac or a mixed mass attached to the cicatrix, and a very thin myometrium between the gestational sac and the bladder wall. Serum beta-HCG dropped to normal in 12 of the 15 patients following treatment with crystalline trichosanthin injected into the cervix followed by oral mifepristone, intramuscular injections of methotrexate, or other appropriate treatment. Two patients underwent total hysterectomy due to massive vaginal bleeding. The remaining patient was misdiagnosed with choriocarcinoma and also had total hysterectomy. CONCLUSION: Pregnancy on a previous lower segment cesarean section scar is rare but very dangerous. Early diagnosis and effective conservative drug treatment may be instrumental in decreasing the occurrence of uterine rupture.