Diagnostic Challenges of Mullerian Anomalies in Pregnancy: A Case Report

Objective: To report a case of pregnancy in rare uterine anomaly and discuss diagnostic challenges of mullerian anomalies during pregnancy. Design: A case report at Promedica Hospital, Toledo, Ohio. Materials and Methods: A retrospective review of the patient’s electronic medical record including consultation notes, imaging studies, and operative findings was performed. Results: A 23-year-old primigravida with known mullerian anomaly presented to the emergency department with positive home pregnancy test and vaginal bleeding. Ultrasound confirmed live intrauterine pregnancy at 12 4/7 gestation, though raised concern for interstitial pregnancy due to eccentric gestational sac location. Subsequent MRI confirmed intrauterine pregnancy in left horn of “bicornuate uterus with single cervix”. Maternal bilateral kidneys were grossly normal. Detailed anatomy ultrasound and pelvic exam with Maternal Fetal Medicine at 16 2/7 gestation confirmed pregnancy in left horn of a complex mullerian anomaly, suspected unicornuate uterus with fused non-communicating right uterine horn with functional endometrium, though differential remained broad given distortion of uterine fundus and cavity by pregnancy. Pregnancy was managed with serial cervical length evaluation via transvaginal ultrasound until 23 weeks and serial growth ultrasounds. Course was complicated by gestational hypertension and fetal malpresentation (footling breech). At 37 weeks and 1 day, patient delivered a healthy female infant (weight 2,580g) via primary cesarean section. Intra-operative evaluation showed normal bilateral tubes and ovaries with midline uterine indention and no connection between left and right uterine horns. Conclusions: Diagnosing mullerian anomalies in pregnancy poses unique challenges due to limitations of diagnostic testing and distortions of uterine cavity and fundal shape by advancing gestation. This case highlights the importance of diagnosing mullerian anomalies pre-pregnancy and cautions against the generalized use of “bicornuate uterus” as a catch-all term for mullerian anomalies, which hinders appropriate counseling.