Uterine Anatomy and Abnormalities

Uterine anatomy and abnormalities at a glance

  • When a woman’s uterine anatomy is abnormal, infertility can result or she may also have problems carrying a pregnancy.
  • Most uterine abnormalities occur before a woman is born, which is called a congenital defect.
  • Infertile women have a greater incidence of uterine abnormalities than do fertile women.
  • The more common congenital uterine abnormalities are disorders of fusion that occur when the two müllerian ducts don’t connect together as a normal uterus with a cavity and two fallopian tubes.
  • Surgery can often correct uterine anatomy disorders and restore or improve fertility. 

What are abnormalities of the uterine anatomy?

A woman’s reproductive organs, including the uterus and fallopian tubes, form at the fetal stage of development before birth. When the structure of the uterus is not properly formed, it’s known as a congenital (present from birth) uterine abnormality. This can result in infertility and difficulty in carrying a healthy pregnancy to term.

Women with uterine abnormalities often experience no symptoms, and the condition is only discovered when doctors evaluate them for infertility or the cause of recurring miscarriages. Some abnormalities can obstruct menstrual blood flow and cause pain as it builds up. Young women usually seek treatment for this pain when their menstruation begins.

Types of uterine anatomy issues

The anatomy of a normal uterus is similar in shape to a “V” or an inverted triangle. The vagina and cervix lead up to the bottom of the V, and the uterine wall surrounds the triangular uterine cavity, which has openings on both sides of the top of this triangle to the fallopian tubes.

Before birth when the uterus forms, problems can arise when the uterus and fallopian tubes do not properly develop from the two müllerian ducts. Such congenital abnormalities are called müllerian abnormalities, and fall into two categories.

Müllerian agenesis is the failure of the uterus and fallopian tubes to form. This is rare, occurring in 1 out of 4,000-10,000 women, according to the American College of Obstetricians and Gynecologists. This is usually detected before puberty. Women with müllerian agenesis can still have sexual activity with proper treatment and counseling, and can conceive a child via in vitro fertilization (IVF) and pregnancy and birth by a gestational carrier.

More common uterine abnormalities are called disorders of fusion that occur when the müllerian ducts don’t join correctly. This can result in a variety of fusion disorders that fall into two categories: two uterine structures and one structure with internal division. These disorders include:

  • Complete duplication (uterus didelphys), is when two uterine systems develop entirely separately. Sometimes there are two separate vaginal canals.
  • Bicornuate uterus is two uteri that share the cervix and vagina.
  • Unicornuate uterus occurs when one müllerian duct does not develop. Although there is only one smaller uterus with a fallopian tube on one side, there are two ovaries.
  • Septate uterus is when there is residual fibrous tissue in the top center of the uterine cavity.
  • Arcuate uterus is an indentation on the top of the uterus, usually not affecting a woman’s fertility.

The most common abnormalities by far are bicornuate and septate. Women with bicornuate disorders and unicornuate uterus often conceive normally but can be at higher risk of preterm birth and, less often, miscarriages. Septate disorders can cause infertility, repeated miscarriages or preterm birth.

Diagnosis of uterine abnormalities

Investigation into the cause of a woman’s infertility is a primary way uterine abnormalities are discovered. Additionally, seeking a cause of pain from obstructive abnormalities can also cause a woman to be evaluated.

An ultrasound imaging test, particularly a sonohysterogram involving a fluid-contrast image, may reveal a cause for suspicion of a uterine abnormality. A hysterosalpingogram (HSG) is an X-ray procedure using a fluid contrast that fills the uterine cavity, giving a silhouette of the cavity. HSG can show uterine abnormalities and is often the best imaging test to describe the uterine anatomy and structure. MRI is another imaging technique that is used to help define the uterine anatomy when the ultrasound or HSG are not definitive.

The reproductive surgeon carefully evaluates each patient’s sonohysterogram HSG and/or MRI results, along with her clinical history. The surgeon will have an in-depth discussion with the patient about treatment options.

Treatment of uterine anatomy problems

Treatment of the bicornuate uterine abnormalities can range from ongoing observation to abdominal surgery that unifies the two uteri into one. A septate uterus can be surgically corrected by removing the septum with hysteroscopy (the dividing band of obstruction). These uterine surgical corrections are called metroplasty.

Before performing a metroplasty, if the reproductive surgeon is not completely sure whether the abnormality indicated on diagnostic tests is bicornuate or septate, she will first conduct laparoscopy to make that definitive determination. Laparoscopy involves a small incision and the insertion of a camera into the uterus to provide the surgeon with a full view.

If the abnormality is a septate uterus, the surgeon can remove the septum by hysteroscopy, a type of surgery where a camera is placed through the cervix inside the uterine cavity. The septum is excised with either scissors or a needle-point cautery. If it is a very large septum, sometimes a balloon catheter is placed inside the uterine cavity for a week, then removed, to prevent the fibrous tissue from scarring together. Sometimes oral antibiotics and estrogen are given to promote uterine healing. A woman can attempt to get pregnant soon after this procedure and success rates of live birth are very good.

If the abnormality is a bicornuate uterus, the reproductive surgeon may perform an open abdominal surgery (laparotomy or laparoscopy) to unite the duplicate uterine cavities. Surgery is rarely necessary for this condition. Women should wait at least three months after this surgery before trying to conceive, and birth should be by cesarean section.

Risks and considerations of surgical treatment

Risks from surgeries to correct uterine abnormalities are the same as for other surgeries. These include risk of infection, blood loss, pain, scarring and reaction to anesthesia.

Whether to undergo the surgery is an important decision that involves particulars about the individual’s medical history, personal health, need for intervention and potential outcome. These issues will be thoroughly discussed by the reproductive surgeon and the patient.