|Classification and external resources|
A human bicornuate uterus
A bicornuate uterus or bicornate uterus, commonly referred to as a "heart-shaped" uterus, is a type of uterine malformation where two "horns" form at the upper part of the uterus.
A bicornuate uterus is formed during embryogenesis. The fusion process of the upper part of the Müllerian ducts (Paramesonephric ducts) is altered. As a result the caudal part of the uterus is normal while the cephalo part is bifurcated.
There are many degrees of a bicornuate uterus. There is a continuous range of the degree and location of the Müllerian ducts (Paramesonephric ducts) fusion and existence of a spectrum rather than a fixed number of types corresponding to strict medical definitions. Two processes that occur during the embryonic development of the Müllerian ducts - fusion and reabsorption - can be affected to different degrees. The degree can determine the likeliness of a pregnancy reaching full-term.
The occurrence of all types of Müllerian duct abnormalities in women is estimated around 0.4%. A bicornuate uterus is estimated to occur in 0.1-0.5% of women in the U.S. It is possible that this is an underestimate since subtle abnormalities often go undetected. Some intersex individuals who by the look of their external genitalia are legally registered as male may nonetheless have a variably shaped uterus.
Effect on reproduction
Pregnancies in a bicornuate uterus are usually considered high-risk and require extra monitoring because of association with poor reproduction potential.
A bicornuate uterus is associated with increased adverse reproductive outcomes like:
- Recurrent pregnancy loss: the reproductive potential of a bicornuate uterus is usually measured by live birth rate (also called fetal survival rate).
- Preterm birth: with a 15 to 25% rate of preterm delivery. The reason that a pregnancy may not reach full-term in a bicornuate uterus often happens when the baby begins to grow in either of the protrusions at the top. A short cervical length seems to be a good predicter of preterm delivery in women with a bicornuate uterus.
- Malpresentation (breech birth or transverse presentation): a breech presentation occurs in 40-50% pregnancies with a partial bicornuate uterus and not at all (0%) in a complete bicornuate uterus.
- Deformity: Offspring of mothers with a bicornuate uterus are at high risk for "deformities and disruptions" and "malformations."
It is possible to diagnose a bicornuate uterus using gynecologic sonography, specifically sonohysterography, and MRI. However, as there is no indication to do such procedures on asymptomatic women, the presence of a bicornuate uterus may not be detected until during pregnancy or delivery. In a C-section (usually done due to malpresentation) the irregular shape of the uterus can be noticed.
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