The Hormone Relaxin: How Does It Affect Pregnancy?

The preparation of a woman’s body for the process of childbirth occurs even in the early stages of pregnancy. Did you know that a large number of substances are involved in this process? The hormone relaxin is even one of them.

This hormone allows the ‘relaxation’ or softening of ligamentous structures or even the cervix. This facilitates both the growth of the uterus and the delivery itself. Interesting, isn’t it? If you want to know a little more about relaxine, we invite you to read on.

What is relaxin?

Relaxin is a hormone that consists of the union of several amino acids. Before pregnancy, a structure called the corpus luteum — which forms on the surface of the ovary after ovulation — is responsible for its production. After that, the placenta takes over the production of this important substance.

An interesting fact is that this hormone is not exclusive to women. In men, the prostate produces it and it is possible to find it in semen. It will likely facilitate the development of spermatozoa and the fertilization process as such.

The hormone relaxin and its functions during pregnancy

Most of the functions of relaxin have to do with facilitating labor once the time comes. For this reason, its concentrations are usually higher during much of the pregnancy. Below we briefly discuss some of the main effects of this substance.

1. Inhibiting Uterine Contractions

The uterine muscle (the myometrium, which forms the interlayer of this organ) grows enormously during each week of pregnancy. It is also prone to contraction in response to various stimuli, including the presence of oxytocin, which occurs during labour.

However, to avoid contractions that could hinder the proper development of the baby, the release of relaxin coincides with a decrease in myometrial activity. It is of course not the only substance involved, because progesterone also has a similar function.

2. Decreases Collagen Production

Did you know that collagen is one of the most abundant proteins in the human body? It is part of the connective tissue, which is found in various organs and systems. It mainly provides support to many structures, as a kind of ‘base’ on which organs can develop or support themselves.

It makes sense, then, that collagen is an integral part of ligaments. This allows these structures to be ‘softened’ to a certain extent and their flexibility can be increased. The main consequence is that it facilitates childbirth, especially if the babies are large at birth.

3. Relaxin and softening of the cervix

This feature is closely related to the previous one as both make it easier to have vaginal or natural deliveries in the best possible way.

The cervix is ​​the lower part of the uterus that actually extends slightly along the upper part of the vagina. This structure must gradually widen to allow the baby to come out. Can you imagine how difficult childbirth would be without the cervix being flexible enough? Relaxine, in combination with other substances, helps the process to run as smoothly as possible.

Is the administration of the relaxin hormone effective?

Although the effects on the human body have been demonstrated, the administration of synthetic relaxin as a method of facilitating childbirth has not yet been proven.

In this regard, a study conducted by the Cochrane team showed that so far there is not enough evidence to confirm that it helps induce labor or prepare the body for it.

This does not mean that the information we have discussed is not valid. The fact that the administration of relaxin as a drug does not show significant effects does not mean that relaxin produced in the placenta or the corpus luteum does not have its natural effects.

Relaxin, an important hormone

Obviously, pregnancy is a very complex and beautiful process involving many substances so that everything can go as it should.

The relaxin hormone is only a small but important part of this stage in women’s lives, and while it’s not essential that you know it thoroughly, it’s interesting to know what’s going on in the body during these special months.