Sonographic diagnosis of uncomplicated first-trimester pregnancy in the rudimentary horn of a unicornuate uterus.

Although pregnancy in a rudimentary uterine horn is rare, the correct diagnosis of this condition on routine sonographic examination is critical, because its natural history usually involves the rupture of the pregnant horn during the second or third trimester, resulting in life-threatening bleeding. We report a case in which the diagnosis of right unicornuate uterus with a left noncommunicating rudimentary horn was made in the first trimester on routine sonographic examination.