Bicornuate uterus with a rudimentary horn is a rare disability. Pregnancy can accidentally settle inside the rudimentary horn. This malformation is often revealed by a uterine rupture in the second trimester, or it can disguise itself in a misleading form making the diagnosis difficult. Bicornuate uterus should be diagnosed early, on the first trimester ultrasound, and if possible before pregnancy to prevent a dramatic development.