A 31-year-old woman with a previous lower segment caesarean section presents at 8 weeks gestation with painless vaginal bleeding. Transvaginal ultrasound shows an empty uterine cavity and empty cervical canal, with the gestational sac implanted in the anterior myometrium at the level of the internal os, surrounded by thin myometrium and showing trophoblastic flow on colour Doppler. What is the diagnosis?

• A Cervical ectopic pregnancy
• B Interstitial ectopic pregnancy
• C Caesarean scar ectopic pregnancy ✓
• D Low lying intrauterine pregnancy

Explanation

Caesarean scar pregnancy implants into the myometrial defect at the site of the previous hysterotomy in the anterior lower uterine segment. The diagnostic triad is an empty uterine cavity, an empty endocervical canal, and a sac located anteriorly at the isthmic region with a thinned overlying myometrial mantle and peritrophoblastic vascularity. A cervical ectopic lies within the cervical canal itself, an interstitial ectopic occupies the cornual myometrium, and a low lying pregnancy retains a normal myometrial mantle.

Reference: Rumack's Diagnostic Ultrasound, 5th ed.

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Written and medically reviewed by the StethoPrep medical team.