|Classification and external resources|
A human bicornuate uterus
A bicornuate uterus or bicornate uterus (from the Latin cornū, meaning "horn"), commonly referred to as a "heart-shaped" uterus, is a uterus composed of two "horns" separated by a septum. In humans, a bicornuate uterus is a type of uterine malformation, but in some other mammalian species, including rodents and pigs, it is normal.
A bicornuate uterus is formed during embryogenesis. The fusion process of the upper part of the Paramesonephric ducts is altered. As a result the caudal part of the uterus is unitary while the cephalo (upper) part is bifurcated.
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 pregnancy or delivery. In a C-section (usually done due to malpresentation), the irregular shape of the uterus will be apparent.
There are many degrees of a bicornuate uterus. There is a continuous range of the degree and location of the fusion of the paramesonephric ducts, 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 paramesonephric ducts - fusion and reabsorption - can be affected to different degrees. This degree of fusion and reabsorption can determine the likeliness of a pregnancy reaching full term.
The occurrence of all types of paramesonephric 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 figure is an underestimate, since subtle abnormalities often go undetected. Some intersex individuals whose external genitalia are perceived as being 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, such as:
- Recurrent pregnancy loss
- Preterm birth: The rate of preterm delivery is 15 to 25%. A pregnancy may not reach full term in a bicornuate uterus when the baby begins to grow in either of the uterine horns. A short cervical length seems to be a good predictor of preterm delivery in women with a bicornuate uterus.
- Malpresentation (breech birth or transverse presentation): a breech presentation occurs in 40-50% of 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."
- Nicolini U, Bellotti M, Bonazzi B, Zamberletti D, Candiani GB. "Can ultrasound be used to screen uterine malformations?". Fertil Steril. 1987 Jan;47(1):89-93.
- Marten K, Vosshenrich R, Funke M, Obenauer S, Baum F, Grabbe E (2003). "MRI in the evaluation of paramesonephric duct anomalies". Clin Imaging 27 (5): 346–50. doi:10.1016/S0899-7071(02)00587-9. PMID 12932688.
- Acién P, Acién M, Sánchez-Ferrer ML (2008). "Müllerian anomalies "without a classification": from the didelphys-unicollis uterus to the bicervical uterus with or without septate vagina". Fertil. Steril. 91 (6): 2369–75. doi:10.1016/j.fertnstert.2008.01.079. PMID 18367185.
- Byrne J, Nussbaum-Blask A, Taylor WS, et al. (2000). "Prevalence of Müllerian duct anomalies detected at ultrasound". Am. J. Med. Genet. 94 (1): 9–12. doi:10.1002/1096-8628(20000904)94:1<9::AID-AJMG3>3.0.CO;2-H. PMID 10982475.
- Rackow BW, Arici A (2007). "Reproductive performance of women with müllerian anomalies". Curr. Opin. Obstet. Gynecol. 19 (3): 229–37. doi:10.1097/GCO.0b013e32814b0649. PMID 17495638.
- Airoldi J, Berghella V, Sehdev H, Ludmir J (2005). "Transvaginal ultrasonography of the cervix to predict preterm birth in women with uterine anomalies". Obstet Gynecol 106 (3): 553–6. doi:10.1097/01.AOG.0000173987.59595.e2. PMID 16135586.
- Heinonen PK, Saarikoski S, Pystynen P (1982). "Reproductive performance of women with uterine anomalies. An evaluation of 182 cases". Acta Obstet Gynecol Scand 61 (2): 157–62. doi:10.3109/00016348209156548. PMID 7113692.
- Shuiqing M, Xuming B, Jinghe L (2002). "Pregnancy and its outcome in women with malformed uterus". Chin. Med. Sci. J. 17 (4): 242–5. PMID 12901513.
- Proctor JA, Haney AF (2003). "Recurrent first trimester pregnancy loss is associated with uterine septum but not with bicornuate uterus". Fertil. Steril. 80 (5): 1212–5. doi:10.1016/S0015-0282(03)01169-5. PMID 14607577.