Having twins from a unicornuate uterus does not necessitate a reduction, but your doctor may recommend it so that a miscarriage or preterm labor can be avoided. A unicornuate uterus is a congenital malformation of uterine development with relatively small spaces. In the case of a twin pregnancy, the space in the uterus may not always be able to fully accommodate both fetuses as the pregnancy progresses, making it susceptible to miscarriage or preterm labor, premature rupture of membranes, and possibly rupture of the uterus. If a woman with a unicornuate uterus is certain that she has a twin pregnancy, her doctor will usually recommend a reduction in the number of fetuses in order to ensure that one of the fetuses grows and develops smoothly, thus reducing the chances of miscarriage or premature labor, but this should be done under the supervision of a doctor.