A 31-year-old female patient, Gravida 6 Para 3 Abortus 2, presented with vaginal spotting for few days duration. She denied pain, fever, or recent injury. She was unable to recall the date of her last menstrual period. Past medical and surgical history was only significant for 3 prior C-sections.
An ultrasound of the pelvis was performed and demonstrated a gestational sac located within the lower uterine segment with an estimated gestational age of 6 weeks and 2 days. Foetal heart rate was 109 beats per minute. MRI of the pelvis without contrast was performed shortly thereafter for lower uterine segment implantation and demonstrated an enlarged uterus with a gestational sac located in the anterior wall of the lower uterine segment within an area of a prior C-section scar.
Cesarean scar pregnancy (CSP) is a rare pregnancy that develops in the myometrium at the scar of a prior cesarean section . Current data approximates the incidence of CSPs as being 1:1800 to 1:2216 of all pregnancies . Although the exact mechanism is not well understood, the current consensus is that the conceptus bypasses the endometrial lining and implants into the myometrium via small defects that form in the poorly healed fibrous scar tissue due to the poor vascularity of the lower uterine segment [2,3].
Although cesarean incisions heal without complications, the possibility of healing defect during scar formation cannot be discounted . Due to its variable presentation, a low threshold for suspicion should be maintained when diagnosing CSP. Patients with CSP can present with painless vaginal bleeding, abdominal pain, or they can be asymptomatic . Consequently, it is recommended that gravid women with prior C-section undergo screening early in first trimester by transvaginal ultrasonography  since the mean age of gestation on presentation is 7.5 +/- 2.5 weeks .
Ultrasound findings: clearly visualised endometrium in an empty uterine cavity and cervical canal; cesarean scar tissue encompassing a gestational sac which is located in the anterior part of the lower uterine segment; presence of a gestational sac regardless cardiac activity or foetal pole. Since one differential for CSP is an aborting foetus, Doppler studies can help distinguishing them . Aborting foetus lacks circumferential perfusion, a finding which is positive in CSP .
Contrast-enhanced MRI may be utilised when ultrasonography results are equivocal. T2-weighted MR is highly efficacious in distinguishing the scar defect, trophoblastic layer and myometrium . Diagnostic accuracy of MRI is 95% versus 89% for US . Its superior resolution for soft tissue provides higher definition which aids in more accurate interpretation .
Evidence is scarce to suggest an optimal treatment for the management of CSPs. Some of the existing treatment options consist of expectant management, medical therapy or surgical intervention . Although expectant management imposes the least interventional risk, the complications are paramount. These include placenta accreta, uterine rupture and massive haemorrhage . Medical therapy via systemic or localised methotrexate is an effective approach that is less invasive than surgery, however it imposes the risk of haemorrhage due to its slow onset of action and can take months to resolve a CSP . Surgical intervention with either laparotomy or laparoscopy involve creating a wedge resection of the CSP followed by repairing the scar defect .
Written informed patient consent for publication has been obtained.
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