EP24.03: Pregnancy in a non‐communicating rudimentary horn: diagnostic challenges and late sonographic diagnostic criteria

Abstract

Pregnancy in the non-communicating rudimentary horn, in some classifications also called cornual pregnancy is a rare type of ectopic pregnancy with the incidence of 1:80 000. We present a case where the diagnosis such pregnancy was difficult to establish. We seek to share our diagnostic journey supported by interesting imaging and aim to identify diagnostic features applicable in 2nd trimester. A 32 year-old primigravida had her initial booking scan at 11+4 weeks of gestation where a uterus didelphus was suspected with the pregnancy residing in the right sided cavity. Serial scans were carried out in the fetal medicine department with continued uncertainty about the exact anatomy of the uterus and the location of the pregnancy. MRI scans were performed at 18 and 22 weeks which raised the suspicion of an abdominal pregnancy. This suspicion was based on the gestational sac appearing to be very thin, without covering myometrium and lying separate and adjacent to the right rudimentary horn. The placenta demonstrated signs of being attached to the anterior abdominal wall which further complicated the diagnosis. In addition to on-going uncertainty regarding the location of the pregnancy, severe fetal growth restriction was identified from 21 weeks with worsening Doppler studies, which further prompted the decision for delivery at 26 weeks with extensive MDT involvement in the Interventional Suite. A final Ultrasound was performed prior to delivery and based on the following diagnostic features the diagnosis of rudimentary horn pregnancy was made: sliding sign of the sac against other structures; round shape of the sac; vascular tree of the placenta limited to the sac (no invasion to other structures); helpful: review of early pregnancy images – evidence of myometrial layer. Vascular connection between rudimentary horn and the main uterus, typically seen in the 1st trimester, can be challenging to visualise in the 2nd trimester hence was not taken as a compulsory criterion.