Müllerian anomalies are a group of disorders present at birth that affect the female reproductive organs, including the uterus, cervix, fallopian tubes, and upper vagina. These differences can be mild, such as a small indentation in the uterus, or severe, such as missing the uterus and upper vagina. Common signs include not having periods, pain in the pelvis, painful or difficult periods, losing pregnancies, trouble getting pregnant, and sometimes problems with vaginal intercourse.

About 0.1% to 10% of people have müllerian anomalies. They are found in about 8% of people with trouble getting pregnant (infertility) and 13% of those who have lost a pregnancy. The rate is highest—almost 25%—in people who have both infertility and pregnancy loss. The real number may be higher, as many cases are missed because some people do not have symptoms.

Müllerian anomalies can affect a person’s life and health, but effective medical or surgical treatments are available. With the right care, many people with müllerian anomalies can have healthy sex lives and, in many cases, successful pregnancies.

“Improvement in clinical and imaging techniques led to early detection of müllerian anomalies, thus enabling proper treatment and guidance,” says Alla Vash-Margita, MD, a Yale Medicine specialist in pediatric and adolescent gynecology. “These complex patients receive best care in centers of excellence, where specialists with necessary expertise are present as part of one comprehensive team.”

While a baby is developing before birth, the uterus, cervix, fallopian tubes, and upper vagina form from two tubes called müllerian ducts. Usually, these tubes join together to make one uterus, two fallopian tubes, a cervix, and the upper vagina. Sometimes, the müllerian ducts do not form the right way, leading to differences in the uterus, cervix, fallopian tubes, or upper vagina. These differences are called müllerian anomalies.

Types of müllerian anomalies include:

• Müllerian agenesis (Mayer-Rokitansky-Küster-Hauser or MRKH syndrome): The müllerian ducts are not fully developed, so the uterus and/or upper vagina are missing or very small.
• Unicornuate uterus: Only one müllerian duct develops fully, so only one side of the uterus forms. Sometimes, a small piece of uterus called a rudimentary horn is also present, which may or may not connect to the main uterus.
• Uterus didelphys: The two müllerian ducts do not join together, so two separate uteruses form, each with its own cervix. There is often a wall dividing the vagina into two parts.
• Bicornuate uterus: The uterus is not fully joined at the top, so it has two upper sections (horns) instead of one smooth space. There is one cervix and one vagina.
• Septate uterus: A band of tissue (called a septum) divides the inside of the uterus into two parts.
• Arcuate uterus: The top of the uterus has a small dip or indentation. This is considered a normal and typically does not cause problems.
• Longitudinal vaginal septum: A wall of tissue runs lengthwise down the vagina, dividing it into two parts. This often happens with other uterine differences.

Müllerian anomalies can affect periods, sex, and pregnancy. Sometimes, they are found with other organ differences, especially in the kidneys and, less often, the spine.

Müllerian anomalies are often not noticed until puberty, when signs like no periods, pelvic pain, or problems with periods or sex may show up. Sometimes, the difference is found when checking for infertility, lost pregnancies, or pregnancy problems. Some people never have symptoms and only find out about the anomaly during tests or surgery for other reasons.

Doctors do not know exactly why müllerian anomalies happen. They start before birth when the müllerian ducts do not form the right way. Most cases happen by chance and are not passed down in families, but genes may play a part. Some studies show that changes in certain genes may be linked to these anomalies, but no single gene causes all cases. Environmental factors, such as some medicines taken during pregnancy (for example, diethylstilbestrol or DES), can also cause certain types of müllerian anomalies, such as the T-shaped uterus. (DES is a man-made form of estrogen that was given to pregnant women between 1940 and 1971 to try to prevent miscarriage.) In many cases, doctors do not know why the müllerian ducts did not form normally.

Risk factors for müllerian anomalies include:

• Family history of müllerian anomalies
• Changes in genes that affect how the reproductive organs form (such as HOXA10, HOXA13, and WNT4)
• Exposure to certain medicines during pregnancy (such as DES)
• Other congenital anomalies, especially in the kidneys and urinary tract
• Certain syndromes, such as MRKH syndrome, MURCS association (müllerian duct aplasia, renal aplasia, cervicothoracic somite dysplasia), and VACTERL (vertebral, anal, cardiac, tracheoesophageal, renal, and limb abnormalities) syndrome.

Symptoms of müllerian anomalies may include:

• No periods
• Irregular or painful periods
• Pelvic pain, which can come and go
• Painful vaginal sex
• Difficulty with tampon insertion
• Repeated pregnancy loss or miscarriages
• Infertility or difficulty getting pregnant
• Premature birth or early labor
• Unusual position of the fetus during pregnancy
• Difficulty with vaginal intercourse due to vaginal differences
• Unusual vaginal discharge or long periods
• Pelvic mass as a result of trapped menstrual blood collecting in the uterus and/or vagina
• Urinary symptoms if there are also kidney problems

Some people have no symptoms and only find out about the anomaly when being checked for other reproductive or gynecologic issues.

To diagnose müllerian anomalies, your doctor will review your medical history, conduct a physical exam, and order one or more tests.

Your doctor may ask about your periods, symptoms such as pelvic pain, problems with periods, or pain during sex, and may also ask if you have had miscarriages or difficulty getting pregnant, and if anyone in your family has had the reproductive tract differences. During the physical exam, your doctor will look for differences in the genitals, check for a vaginal opening, or feel for lumps in the lower belly. Sometimes, the doctor will also check for kidney or bone problems.

Other tests may include:

• 2D or 3D ultrasound: These scans are often the first step and show the shape of the uterus, cervix, and vagina. Three-dimensional (3D) ultrasound is especially good for visualizing the shape of the uterus and identifying specific anomalies.
• Magnetic resonance imaging (MRI): MRI is usually the best test for diagnosing müllerian anomalies. It provides detailed images of the reproductive organs and can help tell different types apart, as well as identify kidney or pelvic problems.
• Hysterosalpingography (HSG): This test uses X-rays and dye to show the shape of the uterus and if the fallopian tubes are open. It is often used for infertility but does not show the outside shape of the uterus.
• Hysteroscopy: In this procedure, a thin camera is inserted through the cervix to directly view the inside of the uterus and cervix.
• Laparoscopy: This surgery uses a small camera inserted through a tiny cut in the abdomen to look at the outside of the uterus and other pelvic organs. It is used if other tests are unclear or if other problems, like endometriosis, are suspected.
• Kidney ultrasound or other kidney scans: Because kidney problems can happen with müllerian anomalies, kidney scans may be done to check for abnormalities.

There is no single treatment for müllerian anomalies, but many can be managed with treatments tailored to the specific type and severity of the anomaly, as well as the individual’s symptoms and reproductive goals. Treatment may not be needed for people who do not have symptoms or reproductive concerns. When treatment is needed, options may include:

• Vaginal dilation: For missing or short vagina, slowly using dilators (tools that gently stretch tissue) can help make or lengthen the vaginal canal, allowing for comfortable sexual activity. This is often the first treatment and helps most people.
• Surgery: Surgery may be needed to fix differences, remove blockages, or help someone get pregnant. Examples include:
  • Vaginoplasty: Making a new vagina for those who do not have one or have a closed vagina.
  • Septum resection: Removing a wall of tissue that divides the vagina or uterus to allow normal periods or help with fertility.
  • Taking out a small, underdeveloped part of the uterus that does not connect to the main uterus and causes pain or problems.
• Medical management: Medicines may be used to stop menstrual periods and help with pain, especially if surgery is delayed or not possible right away.
• Assisted reproductive technologies: For people who cannot carry a pregnancy because the uterus is missing or very abnormal, options such as in vitro fertilization (IVF) with a gestational carrier (another woman carries and gives birth to the baby) or, sometimes, uterus transplant may be considered.
• Psychological support and counseling: Support is important for people dealing with the emotional effects of müllerian anomalies, including issues with sex, fertility, and self-esteem.

People with müllerian anomalies may have a higher risk for certain problems, including:

• Infertility or difficulty getting pregnant
• Repeated pregnancy loss or miscarriages, especially in the first or second trimester
• Premature birth or early labor
• Unusual position of the baby during pregnancy, such as breech (feet first)
• Obstructed menstrual flow, which can cause pain and blood to build up in the vagina or uterus
• Endometriosis, when tissue like the lining of the uterus grows outside the uterus
• Pelvic masses caused by trapped menstrual blood
• Higher chance of needing a C-section
• Placental problems, such as placental abruption (when the placenta detaches from the uterus wall before delivery) or placenta accreta (when the placenta attaches deeply into the uterus wall and is hard to remove after childbirth)
• Kidney or urinary tract problems, which may occur together with müllerian anomalies
• Emotional effects, such as anxiety, depression, or low self-esteem related to reproductive or sexual health

The outlook for people with müllerian anomalies depends on the type and severity of the anomaly. It also depends on symptoms and whether there are other problems such as kidney or skeletal anomalies. Some people never have symptoms or problems. Others may have trouble with periods, sex, or getting pregnant. People with müllerian anomalies may have a higher risk of infertility, lost pregnancies, or pregnancy problems, but many can have healthy pregnancies with the right care and treatment.

Early diagnosis and a personalized approach to care can help with symptoms, improve quality of life, and support reproductive goals. Emotional support is also important, because living with a birth difference in the reproductive organs can affect self-esteem and well-being. Regular check-ups with a health care team are recommended to watch for problems and provide ongoing support.

“Yale Center for Müllerian anomalies includes specialists in reproductive endocrinology and infertility, pediatric and adolescent gynecology, urogynecology, urology, nephrology, psychology, and child’s life,” says Dr. Vash-Margita. “This team provides comprehensive and holistic clinical care to patients with müllerian anomalies throughout the lifespan. Along with groundbreaking clinical care, we conduct cutting-edge research on genetic causes of müllerian anomalies.”