Let's start the story about the development of the fetus week by week from the very beginning - from the moment of fertilization. A fetus under 8 weeks of age is called an embryo; this occurs before the formation of all organ systems.
Embryo development: 1st week.
The egg is fertilized and begins to actively fragment. The egg travels to the uterus, freeing itself from the membrane along the way.
On days 6–8, the egg is implanted—introduced into the uterus. The egg settles on the surface of the uterine mucosa and, using chorionic villi, attaches to the uterine mucosa.
Embryo development: 2–3 weeks.
The embryo is actively developing, beginning to separate from the membranes. At this stage, the rudiments of the muscular, skeletal and nervous systems are formed. Therefore, this period of pregnancy is considered important.
Embryo development: 4–7 weeks.
The embryo develops a heart, head, arms, legs and tail :) . The gill slit is identified. The length of the embryo in the fifth week reaches 6 mm.
At the 7th week, the rudiments of the eyes, stomach and chest are determined, and fingers appear on the arms. The baby has already developed a sense organ - the vestibular apparatus. The length of the embryo is up to 12 mm.
Fetal development: 8th week.
The face of the fetus is determined; a mouth, nose, and ears can be distinguished. The head of the embryo is large and its length correlates with the length of the body; the fetal body is formed. All the significant, but not yet fully formed, elements of the baby’s body already exist. The nervous system, muscles, and skeleton continue to improve.
The fetus developed skin sensitivity in the area of the mouth (preparing for the sucking reflex), and later in the area of the face and palms.
At this stage of pregnancy, the genitals are already visible. The gill slits die off. The fruit reaches 20 mm in length.
Fetal development: 9–10 weeks.
Fingers and toes already have marigolds. The fetus begins to move in the pregnant woman's belly, but the mother does not feel it yet. A special stethoscope can be used to hear the baby's heartbeat. The muscles continue to develop.
The entire surface of the fetal body is sensitive and the baby enjoys developing tactile sensations by touching his own body, the walls of the amniotic sac and the umbilical cord. This is very interesting to observe on ultrasound. By the way, the baby first moves away from the ultrasound sensor (of course, it’s cold and unusual!), and then puts his hands and heels to try to touch the sensor.
It’s amazing when the mother puts her hand to her stomach, the baby tries to master the world and tries to touch with his hand “from the other side.”