An abnormality of the uterus that I have seen repeatedly this week has been that of a bicornate uterus. This often is not detected in females but often presents as a breech presentation when the woman is pregnant. A bicornate uterus is a failure of the internal genitalia of the uterus to form correctly within the embryo, this can lead to a septum down the middle of the uterus; sometimes resulting in two uteruses.
During embryonic development the urogenital tract developed in the first few weeks after conception. There are two ducts that are present before differentiation occurs; mesonephric (Wolffian) ducts and paramesonephric (Mullerian) ducts. The Y chromosome in males produces testosterone, in the absence of this the mesospheric ducts degenerate. The Y chromosome also leads to the production of the anti-Mullerian hormone which in males causes degeneration of the paramesonephric ducts. Due to the absence of this, the paramesonephric ducts remain. These ducts are described as having three different parts:
- Cranial – develops into the Fallopian tubes
- Horizontal – also develops into the fallopian tubes
- Caudal – fuses together to form the uterus, cervix and upper third of the vagina.
A bicornate uterus occurs when there is incomplete fusion of the two caudal parts of the paramesonephric ducts. This cause two distinct uterine horns opening into a single vagina. This is an asymptomatic abnormality which is why this is rarely discovered prior to pregnancy where it might be picked up on ultrasound scan.