The uterus is normally a pear-shaped organ, 7.5 cm long, 5 cm wide and 2.5 cm deep. It is hollow inside and made of thick muscular walls. The lower part of the uterus extends into the vagina and is called the cervix. The upper part is called the fundus, where the fertilized egg lodges, grows and forms the baby. Approximately 0.1 to 3% of women are thought to have a uterine anomaly. However, the exact rate is not known. Because most women do not have problems conceiving and giving birth, they are not even aware of it.
How is the uterus formed?
There are two pairs of Müller ducts that form the female reproductive structures. These reproductive structures are the oviducts, uterus, cervix and the upper 2/3 of the vagina. The ovaries and the lower 1/3 of the vagina are not formed by Müller ducts, but by different embryologic structures. The complete transformation of the Müller duct into female reproductive structures takes place in three stages.
– Organogenesis This is the period of formation. During this period, one or two Müller ducts may not fully develop. This causes the uterus not to form or to underdevelop or to form a unicornuate uterus.
– Fusion: During this period the Müller ducts merge to form the uterus, cervix and the upper part of the vagina. If there are problems during merger, a bicornuate or didelphic uterus may form.
– Disappearance of the wall: After the Müller ducts merge, a wall develops in the middle. However, this then disappears to form a single uterine cavity and cervix. If this does not disappear, it will cause a wall in the uterus.
What are Uterine Anomalies?
Uterine anomalies are analyzed in 7 groups.
– Hypoplasia/Agenesis : In this group, the uterus is absent or underdeveloped. The most common form is Mayer-Rokitansky-Kuster-Hauser syndrome in which the uterus, cervix and upper part of the vagina are absent. These patients are unlikely to have a baby unless their eggs are implanted in a surrogate mother’s uterus.
– Unicornuate uterus: It is a very rare condition. The incidence rate among all anomalies is 6.3%. It occurs when one of the ducts does not develop completely or almost completely. Half of the uterus is absent and there is only one ovarian duct. The ovaries are usually two. If the developmental defect is not complete, as in 90% of patients, there is a stubby horn-shaped structure.
If this stump becomes blocked, it can become a growing mass. Surgical intervention is therefore necessary. If the normal duct on the opposite side develops properly, pregnancy can occur and be completed. The rate of ectopic pregnancy in the oviduct is 4%, miscarriage is 34%, premature birth is 43% and live birth is 54%. Caesarean section is more common because the position of the baby is not good and uterine contractions are not regular. There are two reasons for the high rate of ectopic pregnancy. The vascular structure in the ovarian canal is more than in the uterus and the sperm has more chance to travel to the opposite side. Sometimes the unicornuate uterus remains stumpy without joining with the horn. The sperm or fertilized egg travels this way and the pregnancy continues there. This causes the uterus to rupture. It is a difficult condition to diagnose.
– Didelphys uterus: It is caused by incomplete fusion of the ducts that will form the uterus. The development of the horns is normal. There are two uterine cavities and a cervix. There may also be a wall in the vagina. There may also be a wall inside the uterus. Since both walls are fully developed, conception and continuation of the pregnancy is not a problem.
– Bicornuate uterus : The shape of the uterus is not pear-shaped, but heart-shaped. It is notched from the top downwards. This narrows the space for the baby to grow. It is caused by a partial problem in the joining of the ducts. The muscle layer of the uterus can extend to the inside or outside of the cervix. If it extends to the inner part, it is called bicornuate unicollis, and if it extends to the outer part, it is called bicornuate bicollis. Didelphysis can be confused with the uterus, to differentiate it, there is adhesion between the two horns, the horns are not fully developed and are slightly smaller. In the didelphid, the horns and cervix are completely separated.
– Septate uterus (wall of the uterus): It is formed when the wall between the two horns does not disappear. It may extend up to the cervix and may be complete or partial. The structure of this wall can be made of muscle or connective tissue. Most commonly, they cause problems in conceiving a baby. It is important to distinguish it from bicornuate uterus. Because they are treated differently. In a septal uterus, the structure is removed by entering the vagina with a hysteroscopy tool. In a bicornuate uterus, if surgery is necessary, it is performed through abdominal access.
– Arcuate (curved) uterus : There is a single uterine cavity. However, although the upper part of the uterus is flat or curved, there is a small slit. This group of uteruses is considered normal because it does not cause problems during pregnancy like the other groups.
– DES (Diethylstilbestrol) anomaly: Between 1945 and 1971, many women were treated with the drug DES to prevent miscarriage. However, the drug was later withdrawn due to anomalies in the baby. In 15% of women treated with DES during pregnancy, their baby girls developed uterine abnormalities. In these people, conditions such as underdevelopment of the uterus, T-shaped uterine cavity, stenosis and swelling of the cervix and increased risk of cancer in the vagina have been observed.
What can a Uterine Anomaly lead to?
Compared to other people, having a uterine abnormality does not make a difference to life expectancy. However, the risks may be increased because of other problems they can cause. In addition to anomalies of the uterus, anomalies of other organs, such as anomalies of the kidneys, can also occur. Depending on the problem it causes, uterine anomalies can be recognized at different periods. In the newborn period or in infancy, it may be recognized as a mass in the abdomen or vagina due to the obstruction it causes. During adolescence, it may manifest itself as delayed menstruation, a mass in the abdomen or abdominal pain. In women of childbearing age, it can cause infertility, repeated miscarriage or premature birth. It is rarely found incidentally in women who have undergone surgery or investigations for other reasons.
Having a wall in the uterus or a forward curved uterus rarely cause problems with fertility. Unicornuate uterus can cause problems in conception. Because there is only one ovarian duct. In general, uterine anomalies cause problems in the continuation of pregnancy rather than conception. Miscarriage is more common in women with anomalies than in women with a normal uterus. But the rates vary according to the type of anomaly. For example, women with a wall in the uterus have a higher risk of miscarriage than women with other abnormalities.
When the structure of the uterus is abnormal, the position of the baby in the uterus is different from normal. Instead of head position, breech position is more common. In such an inverted position, cesarean delivery is preferred because normal delivery is risky. Especially women with unicornuate uterus are more likely to have problems during pregnancy and delivery. Women with unicornuate or bicornuate uterus are at risk of premature birth. This is because there is not enough room for the baby to grow and the growing baby overstretches the walls of the uterus, triggering labor. The cervix is also not strong enough to keep the baby inside. It opens much earlier than it should, allowing the baby to be born. This is also called a weak cervix.
What are the Problems During Pregnancy?
Uterine anomalies are not very common. However, when they are the cause of infertility, they are usually treatable. They can also cause recurrent miscarriages, growth retardation in the womb, improper positioning of the baby in the abdomen, premature birth and uterine twinning. If you have an anomaly in your uterus and you have become pregnant, you may be concerned about your condition. Especially if you have had a previous pregnancy that ended in miscarriage. It is therefore important that you attend your check-ups properly and frequently. In the meantime, try to relax and find something to keep you busy. Ask your doctor carefully about the signs of preterm labor. This way, if your baby decides to be born prematurely, you will know what is happening and can get to the hospital as soon as possible. Do not hesitate to call your doctor if you feel unwell or uncomfortable.
How is the diagnosis made?
If you are having trouble conceiving a child, you will first be asked some questions and examined. Then some tests are necessary. Ultrasound can detect most abnormalities in the uterus. It is done through the abdomen or vagina. Sometimes a radiopaque substance called hysterosalpingography (HSG) is injected into the uterus and X-rays are used to visualize the uterus and ovarian ducts. Magnetic resonance imaging (MRI) is also an important test to evaluate the uterus and other internal organs. It can also be used to check for other abnormalities (such as kidneys). Sometimes laparoscopy is necessary. In this test, an endoscope is inserted into the abdomen and the uterus and ovarian ducts are directly visualized.
How is the treatment done?
Some abnormalities are easily treatable, others are risky. For example, if there is a wall in the uterus, your uterus may be damaged during the procedure to remove it and you may have problems conceiving. However, if this procedure is done with hysteroscopy, the uterus is less damaged and your chances of pregnancy are not greatly reduced.