True unicornuate uterus

True unicornuate uterus is a congenital uterine anomaly classified as a Müllerian duct malformation in which only one side of the paired Müllerian (paramesonephric) ducts develops normally, while the other duct fails to develop entirely. This results in a uterus that has a single horn (cornu) with a single fallopian tube on one side, and the contralateral Müllerian structures are completely absent. Unlike other forms of unicornuate uterus where a rudimentary horn may be present, the true unicornuate uterus (also known as unicornuate uterus without a rudimentary horn, or Class U4a in the ESHRE/ESGE classification) has no remnant of the contralateral horn. The condition primarily affects the female reproductive system. Many individuals with a true unicornuate uterus are asymptomatic and may not be diagnosed until they experience reproductive difficulties. Key clinical features include an increased risk of adverse obstetric outcomes such as recurrent miscarriage, preterm labor, preterm delivery, malpresentation of the fetus, and intrauterine growth restriction. Ectopic pregnancy may also occur. Some patients may experience dysmenorrhea. Because only one Müllerian duct develops, the ipsilateral kidney on the affected (absent) side should be evaluated, as renal agenesis or other urinary tract anomalies are commonly associated with this condition. There is no surgical correction that can create a normal bicornuate or typical uterine cavity from a true unicornuate uterus. Management focuses on close obstetric monitoring during pregnancy to detect and manage complications such as preterm labor, cervical insufficiency, and abnormal fetal presentation. Cervical cerclage may be considered in selected cases. Diagnosis is typically made through imaging modalities such as 3D transvaginal ultrasound, hysterosalpingography, or magnetic resonance imaging (MRI), which is considered the gold standard for characterizing Müllerian anomalies.

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