Müllerian anomalies (MRKH, septate uterus, imperforate hymen) !

Birth differences in how the uterus, cervix and vagina form. Some cause missing periods or painful blood build-up; others cause miscarriage.

Updated 2026-11-01

Structures involved

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Why it happens

Sex determination and differentiation

What it is

Congenital malformations of the female reproductive tract caused by failed formation, fusion or resorption of the paired Müllerian (paramesonephric) ducts, together with related outflow defects such as imperforate hymen and transverse vaginal septum.

Who gets it

Müllerian anomalies are found in a few percent of women overall and more often in women with recurrent miscarriage or infertility. MRKH syndrome affects about 1 in 4,500 female newborns and is the second most common cause of primary amenorrhoea after gonadal dysgenesis. Septate uterus is the most common structural uterine anomaly.

Causes

Agenesis or hypoplasia of the Müllerian ducts (MRKH syndrome: absent uterus and upper vagina)
Failed fusion of the two ducts (unicornuate, didelphys and bicornuate uterus)
Failed resorption of the midline septum after fusion (septate uterus)
Failed canalisation of the vaginal plate or hymen (imperforate hymen, transverse vaginal septum)
Mostly sporadic; occasional familial cases and intrauterine diethylstilbestrol exposure (T-shaped uterus)

Risk factors

Family history of reproductive tract anomalies (rare)
Associated renal anomalies (unilateral renal agenesis, pelvic kidney)
Skeletal anomalies of the spine (MRKH type 2)
In utero exposure to diethylstilbestrol (historical)

Pathophysiology

The uterus, cervix and upper vagina develop from the paired Müllerian ducts, which elongate, fuse in the midline and then lose the dividing septum; the lower vagina comes from the urogenital sinus. Because ovaries form separately from the gonadal ridge, ovarian function and secondary sexual characteristics are normal. When the ducts fail to form, the uterus and upper vagina are absent (MRKH); when they fail to fuse or to resorb the septum, the uterine cavity is doubled or divided, which impairs implantation and placental growth. When the outflow tract stays closed, menstrual blood collects behind the obstruction (haematocolpos). Close embryological links with the mesonephric duct explain the frequent kidney anomalies.

Classification

Agenesis/hypoplasia: MRKH syndrome (typical with normal ovaries, 46,XX karyotype)
Fusion defects: unicornuate, didelphys and bicornuate uterus
Resorption defects: septate and arcuate uterus
Outflow obstruction: imperforate hymen and transverse vaginal septum

Symptoms and signs

Primary amenorrhoea with normal breasts and pubic hair (MRKH or outflow obstruction)
Cyclic monthly pelvic pain without bleeding (obstructed outflow)
Bulging bluish membrane at the introitus (imperforate hymen with haematocolpos)
Pelvic or abdominal mass, urinary retention or constipation from a distended vagina
Recurrent miscarriage, preterm birth or malpresentation (septate or bicornuate uterus)
Inability to have penetrative intercourse (vaginal agenesis)

Diagnosis

Clinical: Examination of the external genitalia (bulging hymen, blind or short vagina) in a girl with primary amenorrhoea and normal puberty; normal pubic and axillary hair helps separate MRKH from androgen insensitivity.
Tests: Pregnancy test, FSH, LH, oestradiol and prolactin to exclude hormonal causes of amenorrhoea; karyotype (46,XX in MRKH) and testosterone when androgen insensitivity is possible. Renal function and urinalysis when kidneys are involved.
Imaging: Pelvic ultrasound (including 3D) and MRI define the uterus, vagina and obstruction; MRI or 3D ultrasound separates septate from bicornuate uterus by the outer fundal contour. Renal ultrasound in every case. Hysteroscopy and laparoscopy for selected cases.

Differential diagnosis

Complete androgen insensitivity syndrome (46,XY, scant pubic hair, blind vagina)
Turner syndrome and other gonadal dysgenesis (raised FSH, absent puberty)
Functional hypothalamic amenorrhoea
Labial adhesions or Bartholin cyst
Ovarian tumour or other pelvic mass

Goal of treatment

Relieve obstruction promptly, create a functional vagina when absent, improve pregnancy outcomes where the cavity is abnormal, look for associated renal anomalies, and support the patient psychologically.

Treatment

Surgical: Imperforate hymen: hymenotomy or hymenectomy to drain the retained blood; transverse vaginal septum: surgical excision with reconstruction.
Conservative: MRKH: graduated self-dilation of the vaginal dimple is the first-line way to create a functional vagina.
Surgical: MRKH when dilation fails: surgical vaginoplasty; septate uterus with poor pregnancy outcomes: hysteroscopic resection of the septum.
Follow-up: Renal and skeletal assessment, obstetric surveillance in pregnancies with a uterine anomaly (preterm birth, malpresentation, cervical insufficiency), and fertility counselling (gestational surrogacy or uterus transplantation for MRKH).
Lifestyle: Psychological support and peer counselling for the patient and family, especially at diagnosis of MRKH.

Complications

Haematocolpos and haematometra with retrograde menstruation and endometriosis
Urinary retention and hydronephrosis from a distended vagina
Recurrent miscarriage, preterm birth and malpresentation
Infertility and absolute uterine factor infertility (MRKH)
Psychological distress and impaired sexual function

Prognosis

Outflow obstructions are cured by surgery, ideally before endometriosis develops. Women with MRKH can achieve satisfactory sexual function with dilation or surgery, and genetic parenthood is possible through gestational surrogacy because the ovaries work normally. Resection of a septum improves live-birth rates in women with poor obstetric history.

Prevention

Not preventable
Early recognition of imperforate hymen at newborn or prepubertal examination avoids obstruction later

Test yourself

Think of the answer, then tap the question to see it.

A 16-year-old with normal breasts and pubic hair has never menstruated and has a blind vaginal pouch. Karyotype 46,XX. What is the likely diagnosis?

Mayer-Rokitansky-Küster-Hauser syndrome (Müllerian agenesis); ovaries and hormones are normal.

Which organ system must always be imaged in a patient with a Müllerian anomaly?

The kidneys, because renal agenesis or ectopy often coexists.

A 13-year-old has monthly pelvic pain, no menses and a bulging bluish membrane at the introitus. What is the treatment?

Imperforate hymen with haematocolpos: hymenotomy to drain the blood.

Which uterine anomaly is most common and most associated with recurrent pregnancy loss, and how is it treated?

Septate uterus; hysteroscopic resection of the septum.

How is MRKH distinguished from complete androgen insensitivity?

MRKH is 46,XX with normal pubic hair and normal testosterone; androgen insensitivity is 46,XY with scant pubic hair and male-range testosterone.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Mayer-Rokitansky-Küster-Hauser syndrome: MedlinePlus Genetics (MedlinePlus (U.S. National Library of Medicine), 2024); Absent menstrual periods - primary: MedlinePlus Medical Encyclopedia (MedlinePlus (U.S. National Library of Medicine), 2024).

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Representative model, for educational purposes only.

Body of uterus highlighted on the Durgical 3D model