Uterine anomalies: bicornuate, septate, didelphys, Müllerian agenesis !

Malformation

The uterus forms when two tubes join; if they never join, join halfway or never form, the uterus ends up double, divided or absent.

Updated 2026-11-01

See it in 3D: Body of uterus · Fundus of uterus · Cervix · Vagina · Uterine tubes · Ovaries · Kidneys

What it is

Müllerian anomalies are errors in the formation, fusion or septal resorption of the paramesonephric ducts. They range from the septate uterus, the commonest, to complete agenesis of the uterus and upper vagina (Mayer-Rokitansky-Küster-Hauser syndrome). They usually show up as amenorrhoea, infertility, pregnancy loss or preterm birth, and often come with kidney anomalies.

Embryological cause

Weeks 6–8: the Müllerian ducts form beside the Wolffian ducts; if one fails to form or elongate, a unicornuate uterus results.
Weeks 9–12: the caudal ends fuse in the midline; absent fusion gives uterus didelphys and partial fusion a bicornuate uterus.
After fusion, the septum between them must resorb from below upward; if it persists, the uterus is septate or arcuate.
MRKH: the Müllerian ducts fail to develop; the ovary, of separate origin, is normal. The genes involved are not fully known; WNT4 explains one form with hyperandrogenism.
Closeness to the Wolffian duct explains the link with renal agenesis or ectopia.

Markers

HOXA10
HOXA13
WNT4

How it presents

MRKH: a teenager with normal breasts and hair and primary amenorrhoea; short or absent vagina.
Septate uterus: recurrent miscarriage, especially in the second trimester.
Bicornuate or didelphys uterus: preterm birth, malpresentation; sometimes a double vagina.
Obstructed hemivagina: cyclic pain and a pelvic mass after menarche.
Many mild anomalies cause no symptoms and are found during fertility work-up.

Diagnosis

3D ultrasound: shows the outer contour of the uterine fundus and the cavity.
MRI: the standard for classifying and planning; separates septate (smooth outer fundus) from bicornuate (external cleft).
Hysterosalpingography and hysteroscopy: cavity and septa.
Renal ultrasound in every Müllerian anomaly; karyotype in primary amenorrhoea without a uterus to separate MRKH from androgen insensitivity.

Test yourself

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

Which embryological failure produces a septate uterus?

Failure to resorb the septum left between the Müllerian ducts after they fuse.

How is a septate uterus told apart from a bicornuate uterus on imaging?

The septate uterus has a smooth or nearly smooth outer fundal contour; the bicornuate uterus shows an external fundal cleft.

What separates MRKH from complete androgen insensitivity when both have primary amenorrhoea without a uterus?

In MRKH the karyotype is 46,XX with normal ovaries and pubic hair; in complete insensitivity it is 46,XY, with testes and sparse hair.

Why is a renal ultrasound requested for a Müllerian anomaly?

Because the Müllerian ducts depend on the Wolffian duct, which gives rise to the ureteric bud, and renal agenesis or ectopia often coexists.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of embryology

Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.

Sources: Mayer-Rokitansky-Küster-Hauser syndrome: MedlinePlus Genetics (MedlinePlus, U.S. National Library of Medicine, 2024); Embryology, Sexual Development - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.