A double uterus, otherwise known as a uterus didelphys is a congenital uterine defect causing a bifurcation of the lumen of the uterus. It is considered a very rare condition, occurring in only 0.1-0.5% of women in the US, however, this is considered under representative as many women may remain asymptomatic, resulting in nondetection of the condition.
Women with the condition may experience dysmenorrhea and dyspareunia3. The majority of cases remain asymptomatic with no obvious signs of abnormality, however, some women may present with a double cervix, or double vagina depending on the extent of the malformation.
Some cases have been reported concurrent with unilateral hematocolpos and ipsilateral renal agenesis4.
The cause of a double uterus is well understood by medical science. It is caused during embryogenesis when the two Müllerian ducts fail to properly fuse together to form a cohesive uterine lumen.
The two Müllerian ducts then form their own independent, but still conjoined uterus, typically sharing the same cervical opening. In some cases, they may form independent cervical openings and vaginal canals.
Women with the condition may also have defects of the vagina, renal system, or in rare cases, skeletal defects.
The exact cause of the ducts failure to fuse is not well understood.
Women who have a double uterus frequently have successful pregnancies. The condition can increase the risk of miscarriage and premature birth2. In a study of 18 pregnant women with a double uterus, 21% of the pregnancies resulted in a premature birth. 82% of those required a caesarean section with a 67% foetal survival rate3.
Double uterus has also been associated with higher rates of infertility, miscarriage, intrauterine growth retardation and postpartum bleeding5.
It is possible for each uterus to separately gestate and carry a pregnancy to term, independent of each other. It is not uncommon for the deliveries to occur at different times, sometimes days to even weeks apart. Each uterus has the same statistical chance of developing twins, both independent of each other. This means it is possible to develop two separate sets of twins simultaneously, but this is very unlikely.
In 2006, a UK woman with a double uterus gave birth to a pair of identical twins and another infant from a separate egg1.