The development of the female reproductive system occurs when the two halves join in the middle. In some circumstances one half may not develop completely or at all. This may then lead to only half a uterus and one fallopian tube, or one normal half of the uterus and one half that is underdeveloped but still attached to the normal half.
Many women with this anomaly are unaware of the condition unless they have undergone previous pelvic surgery or pelvic ultrasound when not pregnant. Once pregnant, the normal half of the uterus often fulfils the role of both halves of the uterus however there is an increased risk of miscarriage and preterm birth due to reduce ability for the uterus to stretch. This anomaly may also be diagnosed if you have bleeding or pain during early pregnancy if the developing embryo attempts to implant into the underdeveloped uterus.