Intrauterine development of the fetus: the main stages

Intrauterine development of a person is the period from the moment of the formation of a zygote (a fertilized egg) to the birth of a fully formed fetus that is viable outside the womb of the woman.

This period is called antenatal. It lasts for 280 days. The following stages of fetal development are distinguished:

• initial period - characterized by crushing of a fertilized egg, the formation of a blastula and its implantation into the uterine mucosa. Fertilization occurs when the sex cells of a woman and a man merge, in which a zygote with a diploid genetic apparatus is formed. In this case, the sex of the child is determined by the chromosomes of the spermatozoon, which fertilized the egg. So, if he contained an X chromosome, then a girl will be born if Y is a boy. The initial stages of crushing take place in the fallopian tube. The process of implantation is completed by fixing a fertilized egg in the thickness of the mucous layer of the uterus, where further development takes place;

• embryonic period - the formation of the embryo and the laying of its internal organs. Intrauterine development of the fetus at this stage is a process of gastrulation, in which three embryonic leaves are formed. In addition, it is in this period that histo- and organogenesis passes (tissues and organs are laid). The eight-week embryo already weighs about 4 grams. His features are outlined, legs and pens are formed;

• The fetal period is accompanied by the further growth and development of the fetus, which from the third month of pregnancy is already called the fetus. In this period, the nuclei of ossification form in the bones, the skin becomes covered with fuzz, the heartbeat of the fetus begins to be listened to , the woman feels his movements. Intrauterine development of the fetus at this time is characterized by intensive growth processes and tissue differentiation.

The final stage is childbirth. Their onset is provoked by the release of the hormone oxytocin, which is synthesized by the pituitary gland. This hormone provokes contraction of the uterine muscles, which leads to pushing the baby into the small pelvis and the birth canal.

It should be said that intrauterine development of the fetus is characterized by separate critical periods in which there is an increased sensitivity of the embryo to unfavorable external factors. The first three months of pregnancy, as well as childbirth, require increased attention to the condition of the pregnant woman. With the influence of negative environmental factors at this time, the risk of various anomalies and deformities, as well as complications during labor or after birth, increases.

It should also be noted that intrauterine development of the fetus is accompanied by the formation of a unique organ - the placenta, which allows to carry babies in the womb. It is an important way to adapt to environmental conditions. Its main functions are participation in the gas exchange of the fetus, its supply with nutrients and oxygen, and the secretion of hormones that ensure the normal course of the entire period of pregnancy.