Hidden horn: misdiagnosed ectopic pregnancy in a unicornuate uterus.

Congenital uterine anomalies occur as a result of a failure of the fusion and resorption of the Müllerian ducts in utero. Although Müllerian anomalies are relatively uncommon, they can complicate reproductive health and even cause death.We report a case of an asymptomatic Caucasian woman in her 30s who was misdiagnosed with a tubal ectopic pregnancy at 12 weeks 0 days during a routine dating scan, ultimately revealing a right-sided unicornuate uterus with a non-communicating rudimentary horn. The diagnosis of the Müllerian anomaly was made based on two-dimensional sonography and laparoscopy but was eventually confirmed with MRI. Due to the high risk of uterine rupture, intrauterine growth restriction and preterm birth, it was felt continuation of the pregnancy was not advisable. Thus, the woman underwent a laparotomy, during which a left hemi-hysterectomy of the rudimentary horn was performed and the pregnancy was terminated.