What does müllerian mean?
The uterus, fallopian tubes and upper vagina are made up of two partially fused tubes, which, in the embryo, are known as müllerian ducts, named for physiologist Johannes Peter Müller, who first described them in 1830. They are also known as the paramesonephric ducts, and are at first present in embryos of both sexes.
Normally, these ducts run down vertically from flank to pelvic floor in the young embryo and eventually fuse into a double-barreled tube with two loose ends, known as the uterovaginal primordium, or UVP. The double UVP will eventually merge into a single-barreled uterus, cervix and upper vagina, while the loose ends develop into the fallopian tubes. In adulthood, these organs are referred to as the müllerian tract and congenital malformations of this tract are called müllerian anomalies, or MAs.
In the male embryo, in the presence of anti-müllerian hormone (AMH), the müllerian structures disintegrate during early development. They persist in the female because she does not produce AMH.
In the embryo, the müllerian ducts act as scaffolding for the mesonephric ducts, which give rise to the kidneys. Because of this parallel structural relationship, it is common for a kidney or other urinary anomaly to be present with a müllerian anomaly.
What causes müllerian anomalies?
To date, there is no singular cause for müllerian anomalies. Some may be hereditary , others result from an insult to the fetus while in the womb (the T-shaped uterus of fetuses exposed to DES, for example), and still others may be attributed to random mutation. It is important to remember that in our grandmothers and mothers’ generations, many women with this problem were not diagnosed; while up to 4% of women may have a müllerian anomaly, it may be far more common than physicians realize. Only as diagnostic technology improves and women become more aware of their reproductive health will science get a better understanding as to how common these differences really are. In future years, our honest communication with our children will help build a larger base for understanding the causes of this uniqueness.