Caesarean Scar Ectopic Pregnancy: A Case Study

ABSTRACT Caesarean scar ectopic pregnancy (CSEP) occurs when a blastocyst implants into the residual scar from a previous caesarean section delivery, in the anterior lower uterine segment. In this region the endometrium is thin or absent, and may represent a dehiscence of the mucosal margin of the myometrium, with implantation into the myometrium, rather than a fully formed and receptive endometrium. The diagnosis of a caesarean scar ectopic pregnancy presents challenges to sonographers due to the rare occurrence, misinterpretation as a simple low gestational sac implantation, or low pending or progressing miscarriage. Challenges also exist due to the lack of concerning clinical features in otherwise asymptomatic early obstetric (dating) scans. This case study documents CSEP in an asymptomatic patient with unknown last menstrual period (LMP) presenting at a small rural centre for a routine dating scan. The accurate diagnosis requires a combination of technical skill, clinical history, and awareness of the high level of morbidity and mortality. CSEP may be encountered in as few as 1 in 2000 early pregnancy scans. As such it may be considered a rare obstetric complication, and in a general ultrasound workload may only be seen a few times in a whole career. Recognition of this condition is critical to the prompt treatment and optimal outcome.