Müllerian Ducts

The Müllerian ducts are a pair of tubes that develop into the female reproductive organs. This happens while a fetus grows during pregnancy (fetal development).

All fetuses have Müllerian ducts at first. But during sexual differentiation (development of female or male sex organs), that changes. If a hormone called anti-Müllerian hormone (AMH) is present, it prevents the ducts from developing into female sex organs, and male sex organs then develop. If AMH is absent, female sex organs develop.

The Müllerian ducts are also called the paramesonephric ducts.

What is their purpose?

The function of the Müllerian ducts is to develop into the female reproductive system organs, including the:

• Upper section of the vagina
• Cervix (lower portion of the uterus)
• Uterus (organ that menstruates and houses a developing fetus)
• Fallopian tubes (ducts that carry eggs from the ovaries to the uterus)

Where are the Müllerian ducts located?

The Müllerian ducts start developing on top of an embryo’s kidneys (mesonephric kidneys) about three to four weeks into gestation. These early kidneys are temporary. They’re eventually replaced with fully functioning kidneys around 32 weeks into gestation.

While the Müllerian ducts gradually grow on the mesonephric kidneys, cells develop. These cells will form the different layers of the ducts. The layers thicken and grow downward into a long, finger-like projection. Between eight and 12 weeks into gestation, the tips of the Müllerian ducts fuse with the Wolffian ducts. Then, they start to form the beginning of sex organs.

What are they made of?

Müllerian ducts contain epithelial and mesenchymal cells. Epithelial cells line a lot of organs. They help protect organs and absorb and release important substances. Mesenchymal cells are stem cells. They can grow into different types of cells.

What are the common conditions that affect Müllerian ducts?

Most Müllerian duct anomalies (differences) happen because the ducts don’t develop as expected. As a result, Müllerian duct problems are usually present at birth (congenital). But they might not get diagnosed until puberty or adulthood.

Some Müllerian duct anomalies include:

• Müllerian agenesis: The uterus and/or vagina are missing or underdeveloped. Less often, the fallopian tubes are missing or underdeveloped. The most common form of this is Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome.
• Uterine differences: Issues with Müllerian duct development can cause an atypical uterus. Examples include uterus didelphys, septate uterus and bicornate uterus.
• Vaginal septum: If the ducts don’t fuse correctly, a band of tissue can split the vagina into two parts.
• Persistent Müllerian duct syndrome (PMDS): Some males have a genetic disorder that prevents the release of anti-Müllerian hormone. They have typical male reproductive organs. But they also develop a uterus and fallopian tubes.

Müllerian duct anomalies are rare. They’re present in only 0.1% to 3.0% of live births. There’s nothing you can do to prevent them.

Signs that something isn’t working right

Signs of Müllerian duct issues may include:

• Menstruation issues, like painful or prolonged periods or no periods
• Pain with sex or inserting a tampon
• Female infertility
• Kidney problems

Males with PMDS may have undescended testicles or inguinal hernias.

What questions should I ask my doctor?

If you or your child has a Müllerian duct defect, consider asking your healthcare provider the following questions:

• Will puberty and menstruation be normal?
• Does it affect hormones?
• Can it affect fertility?
• What treatments are available?

What’s the difference between the Müllerian ducts and the Wolffian ducts?

The Wolffian ducts (mesonephric ducts) eventually develop into the male reproductive organs, including the:

• Seminal vesicles: Glands that produce semen
• Vas deferens: Tubes that carry sperm
• Epididymides: Tubes that stores sperm

Females have Wolffian ducts, too, but they typically shrink or disappear.