All about the unicornuate uterus

Unicornuate uterus, bicornuate uterus, septate uterus... There are many uterine anomalies, each one having its own specificities and causing different symptoms, such as recurrent miscarriages, difficulties to get pregnant, or fertility disorders.

What is a unicornuate uterus?

The uterus is the organ in which fertilization and development of the embryo takes place. It belongs to 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 usually have two ovaries. A unicornuate uterus is characterized by the fact that it has only one uterine horn. It is smaller in size and has a curved, elongated shape reminiscent of a banana.

There are several types of unicorn uterus:

• The unicorn uterus without rudimentary horn;
• The unicorn uterus with a rudimentary horn and a cavity communicating with the developed side;
• The unicornuate uterus but with a non-communicating cavity on the developed side. This type of uterus can be responsible forendometriosis;
• The unicornuate uterus with a rudimentary horn without cavity.

The unicornuate uterus is also called uterine aplasia.

What are the origins of unicornuate uterus?

Why do we have a unicornuate uterus? To understand where a one-horned uterus comes from and how it is formed, we must go back to the development of the embryo.

Back to the development of the embryo

It is after the spermatozoa and the ovum have fused that the embryo will gradually migrate towards the uterus. This is called nesting. The embryo will then attach itself to the uterine lining to begin its growth.

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

• Theectoblast which will create the nervous system, the mucous membranes, the teeth and the epidermis;
• Theendoblast which will create the digestive and respiratory system;
• The mesoblast which will create the kidneys, the circulatory system and the somites. It is this layer which is in connection with the unicorn uterus.

From the 8th week, it is possible to determine the sex of the baby by ultrasound. Around the 7th week of embryonic development, two scenarios emerge:

• The Müllerian ducts will develop and form the vaginal canal and the uterine tubes. The ducts of Wollf will decrease. In this case, the future baby will be female.
• Under the effect of hormones, the Müller's ducts atrophy and there will be no uterus formation.

From this stage of development of the embryo, abnormalities can appear which can create uterine malformations.

Uterine malformation during morphological differentiation

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 the uterus will take an abnormal shape.

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

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

What is the impact of a unicornuate uterus on pregnancy?

A unicornuate uterus is asymptomatic and does not prevent pregnancy. However, the chances of pregnancy are reduced by 50% since there is only one fallopian tube. Remember that it is the fallopian tubes that are supposed to carry the sperm to the egg. A woman with a single uterus can get pregnant every other month because the ovaries work in an alternating fashion (note that this is not always regular).

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

However, it is absolutely not impossible to get pregnant, it is possible to carry a pregnancy to term with rest, medication to limit uterine contractions and follow-up and care by a specialized gynecologist. The important thing is to follow the advice of your health specialist to ensure that the pregnancy goes as smoothly as possible.

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How is a unicornuate uterus diagnosed?

Often, the diagnosis of a unicornuate uterus is made during a fertility workup, or after an ultrasound. It is more rarely discovered during a pregnancy. Several symptoms may suggest a uterine malformation and potentially a unicornuate uterus, such as:

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

If this is the case for you, talk to your doctor who can order medical tests to check the shape of your uterus.

Is there a treatment for a unicornuate uterus?

There is no specific treatment for a unicornuate uterus. By following the recommendations of health professionals, it is possible to carry a pregnancy to term.

It is advised to be followed on a regular basis by a specialized gynecologist, to get enough rest and in some cases medication can be prescribed to limit the contractions of the uterus.