Pregnancy in a non-communicating, rudimentary uterine horn. A reason for failed therapeutic second trimester abortion.

Anatomical aberrations in the female genital tract are due to maldevelopment of the Müllerian duct system. Various degrees of malformations are described (9). Some of these malformations are discovered during the investigation of amenorrhea, persistent dysmenorrhea or infertility, while others are discovered in connection with obstetrical problems. The incidence of uterine malformations is quoted as 1:1 500-2 000 (8, 11), the incidence of uterus unicollis bicornis being as rare as 1:100 000 (3). There is no unified nomenclature for the rare types of genital malformations. Semmens describes a group consisting of functional uteri of single Müllerian origin, labelled uterus unicollis bicornis with one rudimentary horn (8). Most rudimentary horns are hollow and allow the expansion of an up to 20 weeks pregnancy (3). Few cases of pregnancy in a rudimentary horn have been seen, causing complications during pregnancy and delivery, and when performing therapeutic abortions (2, 3, 4, 5, 6, 12).