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A bicornuate uterus or bicornate uterus (from the Latin ''cornū'', meaning "horn"), is a type of mullerian anomaly in the human
uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. Th ...
, where there is a deep indentation at the fundus (top) of the uterus.


Pathophysiology

A bicornuate uterus develops during
embryogenesis An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...
. It occurs when the proximal (upper) portions of the paramesonephric ducts do not fuse, but the distal portions that develops into the lower uterine segment, cervix, and upper vagina fuse normally.


Diagnosis

Diagnosis of bicornuate uterus typically involves imaging of the uterus with 2D or 3D
ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...
,
hysterosalpingography Hysterosalpingography (HSG), also known as uterosalpingography, is a radiologic procedure to investigate the shape of the uterine cavity and the shape and patency of the Fallopian tubes. It is a special x-ray using dye to look at the womb ( ut ...
, or
magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wav ...
(MRI). On imaging, a bicornuate uterus can be distinguished from a septate uterus by the angle between the cornua (intercornual angle): less than 75 degrees in a septate uterus, and greater than 105 degrees in a bicornuate uterus. Measuring the depth of the cleft between the cornua (fundal cleft) may also assist in diagnosis; a cleft of over is indicative of bicornuate uterus.


Classification

Bicornuate uterus is typically classified based on whether or not the division extends to the external cervical os. Bicornuate uteri with a division above the os are called ''bicornuate unicollis'' and those with a divided os are called ''bicornuate bicollis.'' 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. There is also a ''hybrid bicornuate uterus:'' External fundal depressions of variable depths associated with a septate uterus can be seen by laparoscopy, indicating the coexistence of the two anomalies. These cases are candidates for hysteroscopic metroplasty under appropriate sonographic and/or laparoscopic monitoring. An ''obstructed bicornuate uterus'' showing uni or bilateral obstruction might also be possible. The unilateral obstruction is more difficult to diagnose than the bilateral obstructive. A delay in the diagnosis can be problematic and compromise the reproductive abilities of those cases.


Treatment

Bicornuate uterus typically requires no treatment. In those who do need treatment,
metroplasty Metroplasty (also called Strassman metroplasty, uteroplasty or hysteroplasty) is a reconstructive surgery used to repair congenital anomalies of the uterus, including septate uterus and bicornuate uterus. The surgery entails removing the abnormal ...
is the surgical correction of choice. Women who have recurrent miscarriage with no other explanation may benefit from surgery.


Epidemiology

The occurrence of all types of paramesonephric duct abnormalities in women is estimated around 0.4%. A bicornuate uterus is estimated to occur in 0.1–0.6% of women in the US. 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. Women exposed in utero to
diethylstilbestrol Diethylstilbestrol (DES), also known as stilbestrol or stilboestrol, is a nonsteroidal estrogen medication, which is presently rarely used. In the past, it was widely used for a variety of indications, including pregnancy support for those with ...
(DES) are at risk for this abnormality.


In pregnancy

A bicornuate uterus is an indication for increased surveillance of a pregnancy, though most women with a bicornuate uterus are able to have healthy pregnancies. Women with a bicornuate uterus are at an increased risk of
recurrent miscarriage Recurrent miscarriage is three or more consecutive pregnancy losses. In contrast, infertility is the inability to conceive. In many cases the cause of RPL is unknown. After three or more losses, a thorough evaluation is recommended by American S ...
, preterm birth, malpresentation, disruptions to fetal growth,
premature rupture of membranes Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labor. Women usually experience a painless gush or a steady leakage of fluid from the vagina. Complicat ...
, placenta previa and retained placenta (which can lead to
postpartum hemorrhage Postpartum bleeding or postpartum hemorrhage (PPH) is often defined as the loss of more than 500 ml or 1,000 ml of blood following childbirth. Some have added the requirement that there also be signs or symptoms of low blood volume f ...
). This is due to the distortion of the normal shape of the uterus, distortion of the cervix leading to cervical insufficiency, or under-vascularization of the
endometrium The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The functional layer ...
as the pregnancy requires more blood supply. In some cases, the nonpregnant horn can rupture during labor, necessitating emergency surgery. Fetuses developing in bicornuate uteri are more likely to present breech or
transverse Transverse may refer to: *Transverse engine, an engine in which the crankshaft is oriented side-to-side relative to the wheels of the vehicle *Transverse flute, a flute that is held horizontally * Transverse force (or ''Euler force''), the tangen ...
, with the fetal head in one horn and the feet in the other. This will often necessitate cesarean delivery. If the fetus is vertex (head down), the two horns may not contract in coordination, or the horn that does not contain the pregnancy may interfere with contractions and descent of the fetus, causing
obstructed labor Obstructed labour, also known as labour dystocia, is the baby not exiting the pelvis because it is physically block during childbirth although the uterus contracts normally. Complications for the baby include not getting enough oxygen which may ...
.


Effect on intrauterine device usage

Usage of intrauterine device (IUD) with copper requires one IUD in each horn to be effective in case of bicornuate uterus. The same practice is generally applied when using
IUD with progestogen A hormonal intrauterine device (IUD), also known as a intrauterine system (IUS) with progestogen and sold under the brand name Mirena among others, is an intrauterine device that releases a progestogenic hormonal agent such as levonorgestrel int ...
due to lack of evidence of efficacy with only one IUD. Evidence is lacking regarding progestogen IUD usage for
menorrhagia Heavy menstrual bleeding (HMB), previously known as menorrhagia or hypermenorrhea, is a menstrual period with excessively heavy flow. It is a type of abnormal uterine bleeding (AUB). Abnormal uterine bleeding can be caused by structural abnor ...
in bicornuate uterus, but a case report showed good effect with a single IUD.


References


External links

{{DEFAULTSORT:Bicornuate Uterus Congenital malformations of uterus and cervix