Ultrasound Clinics: Beware the cesarean delivery scar pregnancy

Ectopic pregnancy, or gestation outside the endometrial cavity, is common, occurring in approximately 1 in 100 pregnancies.¹ The most common site is the fallopian tube (95%), but ectopic pregnancy can occur in the abdominal cavity, the ovary, the cervical canal, and within the myometrium. In the past, pregnancy implantation within a previous cesarean delivery scar was considered extremely rare. But with the rising rate of cesarean delivery over the past three decades, cesarean delivery scar pregnancy (CDSP) is not so unusual.

Before 2002, the literature on CDSP consisted of about 18 case reports, which were recently summarized by Fylstra.² Another 45 patients with CDSP at four institutions recently have been reported in three studies.^3-5 Based on single-institution studies, the incidence of CDSP ranges from 1:1,800 to 1:2,656pregnancies.^4,5 Here we describe a case of CDSP that was diagnosed on ultrasound, confirmed by MRI, and treated with methotrexate. Our review highlights the pertinent features of CDSP and treatment options, underscoring the need for heightened awareness of this potentially life-threatening and formerly little-known complication of early pregnancy.

Defining and diagnosing CDSP In 1978, Larsen and Solomon first made the diagnosis of CDSP.⁶ Their patient presented with heavy vaginal bleeding and abdominal pain at approximately 6^1/2 weeks' gestation and was initially thought to have an incomplete abortion. But her bleeding continued after D&C, and laparotomy revealed a 2.5-cm mass consisting of products of conception in the previous cesarean delivery scar that had eroded into the uterine artery.⁶