Rudimentary horn pregnancy.

A case of pregnancy in rudimentary horn is presented, and a discussion of this rare and potentially catastrophic phenomenon follows. The correct diagnosis was only made at laparotomy for acute abdominal pain when the patient was 16 weeks pregnant. Definite clinical palpation of the pregnant uterus together with ultrasonographic evidence of a viable fetus misled the diagnosis. When this condition is suspected the diagnosis may be aided by ultrasound searching of the uterus.