Page created on June 5, 2021. Last updated on January 11, 2022 at 17:47
Congenital abnormalities of the uterus
The uterus is the female genital organ most commonly affected by congenital abnormalities. In general, these abnormalities increase the risk for:
- Mid-trimester abortion
- Preterm birth
- Prolonged labour
- Obstructed labour
- Retained placenta and postpartum haemorrhage
However, many people with these abnormalities have normal pregnancies as well. For this reason, surgical correction is not warranted unless the patient has had problems with pregnancy which are believed to be due to the abnormality.
People with recurrent pregnancy loss should be evaluated for congenital abnormalities of the uterus.
Diagnosis and evaluation
Ultrasound is the first choice to look for these abnormalities, even though US can’t detect or distinguish all the types. Sonohysterography, hysterosalpingography, and hysteroscopy (topic B28) are second choices. MRi or CT is the third choice.
In sonohysterography, fluid is instilled into the uterine cavity and followed up by ultrasound. In hysterosalpingography, contrast is instilled into the uterine cavity and followed up by fluoroscopy.
Because both the female genital tract and the kidney develop from the Müllerian ducts, uterine abnormalities are associated with renal abnormalities, like renal agenesis, horseshoe kidney, etc. The kidneys should be screened for abnormalities.
Arcuate uterus is characterised by a heart-shaped uterus due to an indentation of the endometrium at the uterine fundus. It’s the most common congenital abnormality of the uterus, but it also considered a normal variant (4% of the population) because it is very rarely associated with reproductive failure.
It does not require surgical correction.
Septate uterus is characterised by a uterus with a longitudinal septum which separates the uterine cavity into two. The separation may be partial or complete. It occurs due to incomplete fusion of the two Müllerian ducts. It is the most common congenital abnormality of the uterus after arcuate uterus, and also the one with highest risk for poor pregnancy outcomes and therefore the one which is most frequently met in clinical practice. It notably increases the risk for transverse lie or breech position.
Septate uterus can’t be diagnosed with ultrasound, as in the resting, non-dilated position the uterine cavity is too small to distinguish the septum. With a sonohysterography or hysterosalpingography, fluid is instilled into the uterine cavity, which dilates it, allowing visualisation of the septum.
Uterus didelphys, or double uterus, is characterised by having two uteruses with separate cavities, each with its own cervix and vagina. It occurs due to complete lack of fusion of the two Müllerian ducts. It is uncommon, affecting 1/350 women.
Bicornuate uterus is characterised by a double uterus and either a single cervix (uterus bicornis unicollis) or a double cervix (uterus bicornis bicollis). It occurs due to incomplete fusion of the two Müllerian ducts.
Due to the increased surface area of the endometrium, bicornuate uterus may cause hypermenorrhoea.
Unicornuate uterus is characterised by the failure of one of the Müllerian ducts, causing the uterus to be formed by only one duct rather than the fusion of two. The failed duct may not develop at all, or it may develop as a rudimentary horn with or without endometrium and with or without communication with the normal part of the uterus.
Congenital abnormalities of the vagina
Transverse vaginal septum
If the Müllerian duct fails to recanalize, a transverse vaginal septum can remain in the upper, middle, or lower third of the vagina. This can cause primary amenorrhoea and dyspareunia.
When menarche begins, blood may accumulate behind the septum, causing cryptomenorrhoea and haematocolpos.
It can be diagnosed by transvaginal ultrasound. Treatment is by nonsurgical dilation over 6 – 12 months, or vaginoplasty.
Sometimes the hymen does not perforate. This may lead to similar symptoms as transverse vaginal septum, including primary amenorrhoea and dyspareunia.
It can be diagnosed on physical examination, where a bulging hymen can be seen. Treatment is by excision (hymenectomy).
Congenital abnormalities of fallopian tubes
These are very rare, but the fallopian tubes can be elongated or one of them can be absent. These may lower the fertility or favour ectopic pregnancy.