Bicornuate uterus
Encyclopedia
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.
.
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 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.
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.
A bicornuate uterus is associated with increased adverse reproductive outcomes like:
Previously, a bicornuate uterus was thought to be associated with infertility, but recent studies have not confirmed such an association.
In a C-section (usually done due to malpresentation) the irregular shape of the uterus can be noticed.
Other less reliable imaging methods include hysterosalpingography
and hysteroscopy
; these procedures are typically done during the course of an infertility investigation.
Uterine malformation
A uterine malformation is a type of female genital malformation resulting from an abnormal development of the Müllerian duct during embryogenesis...
where two "horns" form at the upper part of the uterus.
Pathophysiology
A bicornuate uterus is formed during embryogenesisEmbryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...
.
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.
Classification
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.
Epidemiology
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). This rate is estimated around 63% for a bicornuate uterus.
- 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 birthBreech birthA breech birth is the birth of a baby from a breech presentation. In the breech presentation the baby enters the birth canal with the buttocks or feet first as opposed to the normal head first presentation....
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.
Previously, a bicornuate uterus was thought to be associated with infertility, but recent studies have not confirmed such an association.
Diagnosis
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.
Other less reliable imaging methods include hysterosalpingography
Hysterosalpingography
Hysterosalpingography is a radiologic procedure to investigate the shape of the uterine cavity and the shape and patency of the fallopian tubes. It entails the injection of a radio-opaque material into the cervical canal and usually fluoroscopy with image intensification...
and hysteroscopy
Hysteroscopy
Hysteroscopy is the inspection of the uterine cavity by endoscopy with access through the cervix. It allows for the diagnosis of intrauterine pathology and serves as a method for surgical intervention .-Method:...
; these procedures are typically done during the course of an infertility investigation.