First-Trimester Diagnosis and Management of Pregnancies Implanted Into the Lower Uterine Segment Cesarean Section Scar

Abstract

Severe complications might ensue when the placenta is implanted in the uterine scar left by a previous cesarean section. Both placenta previa and placenta accreta are encountered. It is estimated that an abnormally inserted placenta accounts for at least 50% of obstetric hysterectomies. The authors report 18 pregnancies implanted in an existing lower-segment cesarean section scar. These cases were encountered over 4 years, all of them in the first trimester. The population screened were women referred for transvaginal ultrasonography because of suspected early pregnancy complications. The diagnosis rested on an empty uterus; the presence of a gestational sac anteriorly at the level of the internal os covering the site of a previous lower-segment cesarean section scar and Doppler evidence of functional trophoblastic/placental circulation. Medically treated women had 25 mg methotrexate injected directly into the pregnancy through the transvaginal route guided by continuous ultrasound monitoring. They also received a single intravenous dose of 1.5 g cefuroxime and 500 mg metronidazole. Embryocide using potassium chloride was the initial step when embryonic cardiac activity was detected. Surgery consisted of suction curettage, also performed under ultrasound guidance. A saline-filled Foley catheter was used to control heavy intraoperative bleeding by compression. It was left in place for 12-24 hours. The estimated prevalence of cesarean scar pregnancy in this patient population was 1 in 1800. A majority of women had had multiple previous sections. Gestational age ranged from 4-23 weeks. Eight women were initially treated surgically, 7 medically, and 3 expectantly. Surgery succeeded in all cases, although 3 women had significant bleeding. There were no retained products of conception present after surgery in any case. Five of 7 women had a good outcome with medical management but 2 required surgery and blood transfusion. Expectant management succeeded in 1 of 3 cases. Seven women have attempted another pregnancy, and 5 of them went on to have normal singleton intrauterine pregnancies. Women treated in the first trimester for pregnancy in a cesarean section score do much better than those found.in late pregnancy to have placenta previa or placenta accreta. Expectant management seems to be unwarranted. When the patient agrees to be actively treated, local injection of methotrexate and transcervical aspiration are preferable to laparoscopy or laparotomy.