Embryology is the scientific discipline concerned with the development of the embryo and the fetus, that is to say the period of life between fertilization of the egg and birth.

Embryology deals with the development of organisms from conception to birth. This science seeks to describe the observed transformations, but also to explain all the processes – genetic, molecular, hormonal, etc. – who lead them. It aims to understand precisely how a small group of identical cells, all with the same DNA, manage to differentiate from each other, in the right places, to form all the organs and tissues that make up a living being.

We speak more broadly of developmental biology. Embryology specialists very rarely limit themselves to the embryonic period alone, even if it is this which really sees the organs being put in place and the future individual taking shape. This phase only lasts for the first eight weeks of pregnancy. However, many processes continue beyond, when we no longer speak of the embryo but of the fetus, or even after birth. Developmental biologists may even be interested in reproductive biology, that is, what happens before fertilization, in the gametes for example, if that has an impact on what happens afterwards.

As patients, we mainly use the histology-embryology departments of hospitals for:

• infertility problems, female or male: observing the gametes and then the fertilized eggs makes it possible to understand why, in some couples, there is no fertilization, why the eggs fail to implant in the uterus or why the embryos never develop beyond a certain stage. It also offers solutions to preserve fertility in the event of aggressive treatment (against cancer, for example) likely to threaten reproductive function;
• medically assisted procreation (MAP): embryologists prepare sperm for artificial inseminations, or perform all laboratory manipulations necessary for in vitro fertilization (IVF).

Embryologists are also found in preimplantation diagnosis centers, which are consulted by couples at risk of transmitting a serious genetic disease.

Outside of clinical practice, embryology is a growing research discipline. Indeed, we still know little about the cascades of molecular events that regulate the development of an embryo. By improving knowledge in this area, specialists hope to reduce the still too high failure rates of IVF. By improving ART techniques, they could thus limit the number of trials per patient, as well as the risk of twin pregnancy.

Embryology also helps to understand the mechanisms behind certain embryopathies (or congenital malformations). Sometimes the cause of the problem is identified, but not its role. Research is thus being carried out on the chain of disturbances caused by a genetic mutation, which is known to be responsible for a developmental anomaly. Others are trying to understand how the Zika virus causes a decrease in brain size in infected children in utero, or the link between the environment and certain malformations (babies without arms, hypospadias, Etc.).

Understanding the conditions which lead a stem cell to differentiate into a specialized cell (neuronal, cardiac, etc.) is also useful for the development of new cell therapies. Like bone grafting, these regenerative medicine techniques replace deficient tissues in a patient with functional cells.

Several routes are possible. Some are doctors, graduates in reproductive medicine. Others instead studied biology, physiology, biochemistry or genetics before specializing in embryology.