What is Bicornuate Uterus?
Congenital malformations of the uterus, also known as birth defects of the uterus, are caused by errors in the development of Mullerian ducts. These ducts develop to form parts of the female reproductive system.
These variations were first classified in 1979 by Buttram and Gibbons based on how far the Mullerian ducts had failed to properly develop. In 1988, the American Society of Reproductive Medicine (ASRM) improved this classification, breaking the anomalies down into seven classes:
1. Agenesis/hypoplasia (absent or underdeveloped uterus)
2. Unicornuate uterus (a uterus that’s developed on only one side)
3. Didelphys uterus (two separate uteri)
4. Bicornuate uterus (a uterus that’s heart-shaped)
5. Septate uterus (a uterus divided by a wall or septum)
6. Arcuate uterus (mild variant of a normal uterus)
7. Diethylstilbestrol-related anomalies (abnormalities caused by the drug Diethylstilbestrol)
In 2016, the ASRM revised this classification again and placed the arcuate uterus and normal uterus into the same group.
A ‘bicornuate’ uterus is a type of congenital malformation where the uterus is heart-shaped rather than pear-shaped as a result of partial fusion of the Mullerian ducts. This can be further split into two types based on whether the cervix (the lower part of the uterus) is split:
1. Bicornuate unicollis (one cervix)
2. Bicornuate bicollis (two cervixes)
What Causes Bicornuate Uterus?
The exact reasons for changes in the fusion of the Mullerian ducts, which are part of female reproductive development, are not totally understood. These changes might happen because of a mix of genetic reasons and factors from the environment.
Research has tied problems in the uterus (the place where a baby grows inside a woman’s body) to problems in how genes behave. Some specific genes, including Pax, Lim1, Emx2, Wnt4, Wnt9b, have a role in the formation of Mullerian ducts as they develop.
Another group of genes, known as homeobox genes, help regulate the development of these ducts in combination with Wnt7a. Wnt7a, in particular, is important for Hoxa 10 and Hoxa 11 genes to be expressed. The lineup of these genes – Hoxa 9, 10, 11, and 13 – along the Mullerian duct is crucial for the right development of the fallopian tubes, uterus, cervix, and vagina.
Mutations in the HOXA13 gene have been found in a condition known as hand-foot-genital syndrome, which is marked by abnormalities in the limbs and urinary and genital systems, that includes problems with the fusion of the Mullerian ducts.
In addition, environmental factors could play a role. For example, exposure to a specific drug, diethylstilbestrol, during pregnancy (particularly in the 1940s to the 1970s), has been linked to the development of a T-shaped uterus. This is a specific type of problem categorized by the American Society of Reproductive Medicine. However, it’s important to note that this disease is less common now, since the drug isn’t used anymore.
Risk Factors and Frequency for Bicornuate Uterus
A study looked at 94 different research reports to understand how common birth defects are in the general population compared to women who have struggled with infertility or miscarriages. The results showed that 8.0% of women struggling with infertility had uterine abnormalities, compared to 13.3% of those with a history of miscarriage and a significant 24.5% of women with both a history of miscarriage and infertility.
The most common abnormalities observed were an arcuate uterus in the general population and a septate uterus in women who had experienced infertility and miscarriage. The bicornuate uterus, another kind of abnormality, was found in 0.4% of the general population. However, its prevalence increased in specific groups, being found in 1.1% of women with infertility, 2.1% of women with a history of miscarriage, and notably in 4.7% of women with both infertility and miscarriage.
Signs and Symptoms of Bicornuate Uterus
A bicornuate uterus is a congenital abnormality where the uterus has two cavities instead of one. This can sometimes exist on its own, or it can be linked to other genital malformations. When a woman has a bicornuate uterus, it can significantly increase the risk of certain complications related to pregnancy. These include:
- Loss of pregnancy in the first or second trimester.
- Preterm delivery, occurring before 28 weeks.
- Having babies with low birth weight.
- Babies being in the wrong position for birth.
Many women with a bicornuate uterus don’t experience any symptoms during their teenage years. Some may have heavy or painful periods because of the two uterine cavities. Often, the condition gets diagnosed when a woman has a routine check-up while pregnant or experiences complications during pregnancy. The physical exam in these cases is usually normal.
About a quarter of the time, a bicornuate uterus is associated with a longitudinal vaginal septum, which can lead to problems such as painful sex or difficulty controlling menstrual flow with a tampon. In these instances, a physical exam may reveal a vaginal septum, which separates into a double cervix and uterus when removed.
Kidney abnormalities are common in women with a bicornuate uterus due to the linked development of different embryo structures. The most common issue is having one kidney missing, often in cases of a didelphys uterus, but it can also happen with a bicornuate uterus. Other abnormalities may include an ectopic ureter.
In severe cases, a bicornuate uterus with non-communicating uterine cavities can exist along with a missing kidney and a blocked vaginal canal. This can lead to symptoms such as sudden inability to pass urine, pelvic pain, and painful periods. If so, a physical exam might show a bulge in the vagina, making it hard to examine the cervix.
Some patients with a communicating bicornuate uterus, a missing kidney, and a blocked vaginal canal can present with a Gartner duct pseudocyst. The physical exam in these cases would show a cyst in the front and side wall of the vagina.
In some cases, a bicornuate uterus can exist along with a non-communicating uterine horn. These patients might experience infertility due to a condition known as endometriosis, which can occur due to backward flow of menstruation.
Testing for Bicornuate Uterus
Imaging is an important part of diagnosing and managing a condition called bicornuate uterus, which means that the uterus has two horns and appears heart-shaped. There are several ways to do this:
Hysterosalpingography: This is a common method used to assess infertility. It works by introducing a contrast agent (a special dye) through a tube into the uterus. This dye makes the uterus and fallopian tubes visible under X-rays, thus helping to reveal any abnormalities. In the case of a bicornuate uterus, if the angle between the two horns of the uterus is more than 105 degrees, it is classified as bicornuate. However, this method has limitations. It can’t assess the outer surface of the uterus, which is needed to differentiate a septate uterus (where a wall of tissue called a septum goes down the middle of the uterus) from a bicornuate uterus. It’s also limited when a vaginal septum (a wall of tissue in the vagina) is present, which can cause blockages.
Ultrasound: This is the first imaging procedure done when a patient comes to the clinic. It’s cost-effective and noninvasive, with no exposure to radiation. While standard 2D ultrasound is widely used, 3D ultrasonography provides more accurate and reliable results. Using 3D ultrasound, doctors can view the uterus from all angles and separate a bicornuate uterus from a septate uterus with a high degree of accuracy. However, conducting an ultrasound scan requires expertise, and the test may not always be able to identify certain abnormalities of the uterus.
Magnetic Resonance Imaging (MRI): This is considered the gold standard for diagnosing a bicornuate uterus. MRI is noninvasive and doesn’t involve radiation. It can provide images of the uterus, vagina, and other pelvic structures from various angles. This can help doctors determine whether there are any abnormalities in the uterus’s size and shape. However, the most crucial decision using MRI is whether the dip in the uterus is more than 10 mm. If it is, the uterus is likely bicornuate; if not, it can be considered arcuate/subseptate. However, it’s important to know that an accurate diagnosis can only be made by a physician after careful evaluation.
Treatment Options for Bicornuate Uterus
If a woman is identified as having a bicornuate uterus during a normal pregnancy check-up, close monitoring throughout her pregnancy is essential. This is because there’s an increased risk of complications such as premature labor, and the baby being in an abnormal position for birth.
On the other hand, if a woman has a history of multiple miscarriages or premature labor in her previous pregnancies, with a diagnosed bicornuate uterus, a surgical procedure might be recommended. This procedure is called Strassman metroplasty, and was first introduced to medicine in 1907 by Strassman.
In the Strassman metroplasty procedure, a transverse (sideways) incision is made over the upper part of the uterus, being careful to avoid damage. Then, the uterine cavity is opened, and the partition (called the septum) inside the uterus is removed. This converts the two cavities of the uterus into one. The last step is to close the cavity to prevent the lining of the uterus from sticking together.
Nowadays, the Strassman metroplasty procedure is typically done laparoscopically. This means that instead of one big cut, the surgeon makes small incisions and inserts thin tube-like instruments to complete the operation. This kind of procedure has several advantages such as less bleeding, a lower risk of infections, and reduced formation of postoperative adhesions (internal scar tissue that can bind together the internal body structures). This might be attributed to less tissue handling and the tissues not getting dried out during the procedure.
What else can Bicornuate Uterus be?
A bicornuate uterus can sometimes come with a longitudinal vaginal septum, which makes it hard to tell it apart from a different condition known as a uterus didelphys. If this is the case, checking for the existence of soft tissue between two uterine cavities can help confirm a diagnosis of a bicornuate uterus.
Telling a bicornuate uterus apart from a septate uterus using a specific test called hysterosalpingography can be tricky. However, this distinction is essential because the treatment methods for these two conditions are different. For instance, a septate uterus is typically treated through a procedure known as hysteroscopic resection, while a bicornuate uterus involves uniting the uterus. In these situations, an MRI can be used to differentiate between fusion anomalies and resorption anomalies.
What to expect with Bicornuate Uterus
A bicornuate uterus is a condition where the uterus has two separate sections instead of one. This can lead to complications during pregnancy, such as premature labor, recurring miscarriages, and abnormal fetal positioning.
One way to treat this condition is through a procedure known as a Strassman metroplasty. This is usually recommended for women who’ve had recurring miscarriages. In a seven-year study, this procedure significantly improved fetal health, with healthy pregnancies increasing from 0% to 80%.
These days, a less invasive version of the procedure, called laparoscopic metroplasty, is becoming more popular. In one study, after undergoing laparoscopic metroplasty, 85% of patients were able to successfully achieve pregnancy. Seven women with a bicornuate uterus were able to carry their pregnancies from twelve weeks right through to full term.
Another benefit of laparoscopic metroplasty is that it can reduce the amount of scarring in the uterus and improve its flexibility, which can further decrease the risk of complications.
Possible Complications When Diagnosed with Bicornuate Uterus
Women with a bicornuate uterus, also known as a heart-shaped womb, may face several complications.
One of the most common issues is premature labor. With a shorter-than-average cervix (less than 25mm as per ultrasound), the risk of early delivery is 13 times more. However, there’s a procedure called “cervical cerclage” that could effectively help in preventing premature birth.
Another challenge could be excessive bleeding after childbirth, also known as postpartum hemorrhage. Although there are several surgical and non-surgical means to manage this, they come with their set of advantages and disadvantages. The non-surgical method using a Bakri Balloon is proven effective. In comparison, surgical methods such as B lynch suturing and conduit ligation might affect neighboring structures. Also, ligation might not work effectively due to the multiple blood supply to the uterus during pregnancy.
Moreover, first-time pregnant women with a bicornuate uterus have an increased risk of uterus rupture. This might be due to abnormal development in the lower part of the uterus or a fibrous band between the two sections of the uterus limiting its expansion and therefore, risk of rupture.
Also, because womb abnormalities often co-exist with kidney issues, there’s a higher risk of high blood pressure during pregnancy. This makes it essential to regularly monitor blood pressure in pregnant women with a bicornuate uterus.
Lastly, while a bicornuate uterus isn’t directly linked with endometrial (uterine lining) cancer, it can hide cancer signs. For instance, a biopsy from the healthy portion of the womb could give false-negative results, leading to delayed diagnosis and worsening patient outlook. Therefore, if a woman with a bicornuate uterus experiences uterine bleeding, an MRI may be crucial in diagnosing the issue.
Common Complications:
- Premature labor
- Excessive bleeding after childbirth
- Risk of uterus rupture, especially in first-time pregnancies
- Increased risk of high blood pressure during pregnancy
- Potential delay in diagnosing endometrial cancer
Preventing Bicornuate Uterus
A bicornuate uterus is an unusual condition that not many women have. When a woman is diagnosed with this, it’s very important to make sure she fully understands what it means. Most of the time, women find out they have a bicornuate uterus when they’re pregnant. Because of this, it’s essential to discuss with them what this might mean for their pregnancy and future pregnancies.
Prenatal care (care during pregnancy) should be more in-depth and detailed. The pregnant woman should also be taught about the warning signs of preterm labor (giving birth too early). Another essential point to mention is the risk of uterine rupture (the uterus breaking open) during labor. This is a serious risk that comes with having a bicornuate uterus.
Abnormal baby positions are highly common when a woman has a double uterus. So, the woman should also be counseled about the likelihood of having a cesarean section (or C-section, where the baby is delivered through a surgical cut in the stomach and uterus) in the future.
