Cesarean scar ectopic pregnancy

Cesarean scar ectopic pregnancy is a rare type of abnormal implantation. It is often considered the rarest type of ectopic pregnancy, although some do not include it in this category as implantation occurs within the uterus, instead preferring the term "cesarean scar pregnancy" ⁶.

Epidemiology

It has an estimated incidence of ~1:1800-2200 pregnancies ^2,3. The overall incidence is however thought to be increasing ⁴, representing up to 6% of ectopic pregnancies in patients with a history of cesarean section ¹¹.

Pathology

Poor healing can result in a focal thinning of the scar, which may be susceptible to implantation of the gestational sac at this point rather than in the endometrial cavity ¹⁰. 

Radiographic features

Ultrasound

Described sonographic features include:

• empty uterus
• empty cervical canal
• development of the gestational sac in the anterior part of the lower uterine segment
• an absence of myometrium between the bladder wall and the gestational sac

Treatment and prognosis

Ultrasound-guided methotrexate injection has emerged as the treatment of choice. Surgical or invasive techniques, including dilatation and curettage, are not recommended due to high morbidity and poor prognosis. Because subsequent pregnancies may also be complicated by uterine rupture, the uterine scar should be evaluated before, as well as during the subsequent pregnancies.

Complications

• uterine rupture
• massive hemorrhage

Differential diagnosis

On ultrasound consider:

• an anterior cervical ectopic pregnancy can have some similar features
• prominent cesarean section scar tissue
• miscarriage in progress