Implantation of a gestational sac in a cesarean section scar

A 39-year-old asymptomatic woman, gravida 5 para 4, presented for routine ultrasonography in her 7th week of gestation. Her medical history was unremarkable, except for four low, transverse cesarean sections. A gestational sac implanted in the anterior cervico-isthmic wall was demonstrated by ultrasonography. It contained an embryo with cardiac activity. Implantation was in the scar tissue, which had a rich blood supply, as demonstrated by a second ultrasound study. The serum hCG level was 11,306 mIU/mL. Magnetic resonance imaging confirmed that the gestational sac had implanted in the thin cesarean scar tissue, without protruding out of the uterine wall. The sagittal T1 image is presented in Figure 1 (Ut 5 uterus; Cx 5 cervix; Bl 5 urinary bladder; V 5 vagina; GS 5 gestational sac). The ectopic pregnancy was terminated by the administration of systemic methotrexate (four doses of 1 mg/kg given on alternate days with alternating days of folinic acid), as described by Hajenius et al. (1). The patient tolerated the treatment well without complications. The cardiac activity disappeared, the sac gradually shrank, and the serum hCG levels decreased to 0. Case reports of an ectopic implantation of a gestational sac in a thin-walled uterine cesarean section scar, leading to a risk of uterine rupture, have been previously described. Most of them were diagnosed by ultrasonography, some of them also by magnetic resonance imaging. In quite a few cases, urgent hysterectomy was performed because of uncontrollable hemorrhage, either spontaneous or iatrogenic.