All about the unicornuate uterus

Unicornuate uterus, bicornuate uterus, septate uterus... There are numerous uterine anomalies, each with its own specific characteristics and giving rise to different symptoms, such as recurrent miscarriage, difficulty in getting pregnant, or fertility problems.

What is a unicornuate uterus?

The uterus is the organ in which fertilization and embryo development take place. It is part of the female reproductive system. It contains the cervix.

A uterus is called a unicornuate uterus when it is connected to only one fallopian tube. However, women generally have two ovaries. In fact, a unicornuate uterus is characterized by the fact that it has only one uterine horn. It is smaller in size, with a curved, elongated shape reminiscent of a banana. 

There are several types of unicorn uterus:

• Unicorn uterus without rudimentary horn;
• The unicornuate uterus with a rudimentary horn and a communicating cavity on the developed side;
• The unicornuate uterus, with a non-communicating cavity on the developed side. This type of uterus can be responsible forendometriosis;
• The unicornuate uterus with a rudimentary horn and no cavity.

The unicornuate uterus is also known as uterine aplasia.

What are the origins of unicornuate uteri?

Why do we have a uniform uterus? To understand where and how a unicornuate uterus is formed, we need to go back to the development of the embryo.

Back to embryo development

Once the sperm and egg have fused, the embryo gradually migrates to the uterus. This is called nesting. The embryo then attaches itself to the uterine mucosa and begins to grow.

Between the second and third week of pregnancy, lhe embryo is made up of 3 layers that will develop different tissues and organs:

• Theectoblast, which creates the nervous system, mucous membranes, teeth and epidermis;
• Theendoblast, which creates the digestive and respiratory systems;
• The mesoblast, which creates the kidneys, circulatory system and somites. This layer is linked to the unicornuate uterus.

From the 8th week, it is possible to determine the baby's sex at l. Around the 7th week of embryonic development, two scenarios emerge:

• The Müller ducts expand to form the vaginal canal and fallopian tubes. Wollf's ducts will diminish. In this case, the future baby will be female.
• Under the effect of hormones, the Müllerian ducts atrophy and no uterus is formed.

From this stage of lembryo development onwards, abnormalities may appear, leading to uterine malformations.

Uterine malformation during differentiation morphology

As we have just seen, it is during the morphological differentiation of the genital tract that uterine malformations occur. When the Müllerian ducts do not evolve correctly lthe uterus takes on an abnormal shape.

The unicornuate uterus remains a rare congenital malformation. There are also other types of uterine malformation, such as :

• Thebicornuate uterus, which is the result of poor fusion of the Müllerian ducts; the horns are smaller for a bicornuate uterus.
• Theseptate uterus: during embryonic and uterine development, the septum separating the Müllerian ducts must normally disappear, otherwise the uterine cavity is divided in two. The septate uterus is responsible for infertility, and this malformation is more frequent than the unicornuate uterus;
• Thedidelphic uterus, when there are two uteruses and potentially a double vagina if the uterus is bicervical;
• lM ayer-Rokitansky-Küster Hauser (MRKH) syndrome, also known as mullerian agenesis-aplasia, refers to the condition of being born without a uterus or vagina, and is usually diagnosed in adolescence following amenorrhea (absence of periods). It is very difficult to become pregnant with this type of malformation.

What impact does a unicornuate uterus have on pregnancy?

A unicornuate uterus is asymptomatic and does not prevent pregnancy. However, as there is only one fallopian tube, the chances of pregnancy are reduced by 50%. The fallopian tubes are responsible for carrying sperm to the egg. A woman with a unicornuate uterus can become pregnant every other month, since the ovaries function alternately (although not always regularly).

If fertilization takes place and the fetus develops, complications may arise, such as growth retardation, ectopic pregnancy, premature delivery, miscarriage, etc...

But it's by no means impossible to get pregnant, and it is possible to carry a pregnancy to term with rest, medication to limit uterine contractions and follow-up by a specialized gynecologist. The important thing is to follow the advice of your health specialist to ensure that your pregnancy goes as smoothly as possible.

How is a unicornuate uterus diagnosed?

The diagnosis of a unicornuate uterus is often made during a fertility test, or after an ultrasound scan. More rarely, it is discovered during pregnancy. Several symptoms may point to a uterine malformation and potentially to a unicornuate uterus, such as :

• Difficulty getting pregnant;
• Fertility disorders;
• Repeated miscarriages.

If this is the case, talk to your doctor, who may prescribe medical tests to check the shape of your uterus.

Is there a treatment for unicornuate uterus?

There is no specific treatment for a unicornuate uterus. If you follow the recommendations of your health professionals, you can carry your pregnancy to term.

It's advisable to be monitored regularly by a specialized gynecologist, to get enough rest and, in some cases, to take medication to limit uterine contractions.