Uterine Anomalies: Bicornuate, Septate, and Unicornuate Uterus

Introduction

• Description: Uterine abnormalities are characterized by the incomplete formation of the uterus, resulting in one or two separate halves or horns or a single uterus with a central septum. The central septum may divide the uterine cavity either partially or completely. The two resulting halves may be of unequal size or volume. In its most extensive form, duplication of the cervix and vaginal canal also may occur. These abnormalities are associated with renal agenesis and blind vaginal pouches that may become filled with menstrual fluid after puberty, resulting in a painful mass.

• Prevalence: Estimated to be 0.1% of female births. Septate or arcuate uterine anomalies may be present in 3%–5% of women.

• Predominant Age: Congenital.

• Genetics: May be transmitted through polygenic or multifactorial pattern.

  

Etiology and Pathogenesis

• Causes: Failure of the fusion of the Müllerian ducts, which normally occurs near the beginning of the 10th week of gestation. This may vary from septation of the uterus to complete duplication of the uterus, cervix, and vaginal canal. Most septations are because of a failure of the normal processes of the development of the Müllerian system between the 10th and 13th weeks of gestation, when the lower portion of the median septum of the uterus is resorbed, or between the 13th and 20th week, when the upper septum (in the uterine body) is resorbed. In utero exposure to diethylstilbestrol has been associated with a T-shaped uterine cavity similar to the arcuate form of a septate uterus. A unicornuate uterus may result from a failure of the normal formation or the destruction of one of the Müllerian ducts. This may occur if there is a lack of development of the mesonephric system on the affected side resulting in a failure of the associated Müllerian system (in these patients, the ipsilateral kidney and ureter are usually absent).

• Risk Factors: None known.

Signs and Symptoms

• Asymptomatic

• Recurrent abortion (15%–25% of patients with recurrent abortions have uterine abnormalities; there is a 50% risk of pregnancy loss when the uterus is unicornuate)

• Premature labor (20% risk for unicornuate uterus)

• Uterine pain or rupture in early pregnancy

• Abnormal presentation in labor (breech or transverse position)

• Inability to stop menstrual flow using tampons (when there is duplication of the vagina as well)

• When outflow is obstructed—hematometra

• Dysmenorrhea, abdominal pain, pelvic mass, abrupt blood discharge

Diagnostic Approach