In a female fetus, the uterus starts out as two small tubes. As the fetus develops, the tubes normally join to create one larger, hollow organ — the uterus. Sometimes, however, the tubes don't join completely. Instead, each one develops into a separate structure. This condition is called double uterus (uterus didelphys). A double uterus may have one opening (cervix) into one vagina, or each uterine cavity may have a cervix. There may even be two vaginas.
It results from failed ductal fusion that occurs between the 12th and 16th week of pregnancy and is characterised by two symmetric, widely divergent uterine horns and two cervices. The uterine volume in each duplicated segment is reduced. As with most uterine anatomical anomalies, there is an increased incidence of fertility issues, and Müllerian abnormalities in general are over represented in infertile women. The chance of seeing a pregnancy to term is significantly reduced, down to only 20%, with a third of pregnancies ending in abortion and over half in premature deliveries. Only 40% of pregnancies resulted in living children.
Surgery to unite a double uterus is rarely done — although surgery may help you sustain a pregnancy if you have a partial division within your uterus and no other medical explanation for a previous pregnancy loss.
Didelphic uteri account for approximately 8% (range 5-11%) of Müllerian duct anomalies.