Müllerian anomalies

Müllerian duct anomalies are those structural anomalies caused by errors in Müllerian duct development as an embryo forms. Factors contributing to them include genetics and maternal exposure to substances that interfere with fetal development.

Genetic causes of Müllerian duct anomalies are complicated and uncommon. Inheritance patterns can be autosomal dominant, autosomal recessive, and X-linked disorders. Müllerian anomalies can be part of a multiple malformation syndrome. Studies have estimated that Mullerian anomalies can affect between 4 percent and nearly 7 percent of the female population.

Müllerian anomalies occur as a congenital malformation of the Müllerian ducts during embryogenesis. The Müllerian ducts are also referred to as paramesonephric ducts, referring to ducts next to (para) the mesonephric (Wolffian) duct during foetal development. Paramesonephric ducts are paired ducts derived from the embryo, and for females develop into the uterus, uterine tubes, cervix and upper two-thirds of the vagina. Embryogenesis of the Müllerian ducts play important roles in ensuring normal development of the female reproductive tract. However, when defects in each of the three phases of embryogenesis occur, it results in specific structural malformations which are distinguished according to anatomy into seven classes based on the American Society for Reproductive Medicine (ASRM) classification system. Class I and II anomalies result from underdevelopment of the two separate primitive uterine, vaginal and cervical pockets due to an arrest of stage one of organogenesis, resulting in underdevelopment of both left and right primitive uterus (class I) or underdevelopment of one of the primitive uterus (class II). Class III and IV anomalies result from failure of midline fusion of the two separate primitive pockets due to an arrest of stage two of organogenesis. Class V and VI anomalies result from failure of degeneration of the midline due to an arrest at stage three of organogenesis. Class VII anomalies are malformations caused by Diethylstilbestrol (DES).