The intrauterine development of a child begins immediately after conception, for literally a few seconds after that, there is a living human in the woman’s body. It may not be very similar to an adult yet, but it has exactly the same set of chromosomes as a newborn baby. I, as a pediatrician, know this for sure!
So, from the moment of conception, the very first period of intrauterine development begins – blastogenesis. This period lasts only fifteen days.
Thirty hours after fertilization, the first cell division occurs, followed by one division per day. On the fourth day, the baby reaches the uterus. The cells begin to divide very intensively, and on the seventh day the embryo penetrates the uterine wall. It lasts about forty hours.
Mom at this point usually begins to show the first signs of pregnancy. I have never had any first signs of pregnancy.
Two weeks after conception, I went to the ultrasound, and they confirmed that I was pregnant, and even made the first photo!
By the end of the second week, the formation of internal organs begins. Now the future baby is most susceptible to various actions of the external and internal environment.
From the sixteenth day to the thirteenth week begins the second period of development – the embryonic. Almost immediately there is a laying of the heart and nervous system. In the fourth week, the kidneys, intestines, bones, muscles, ears, eyes, thyroid, liver and throat are laid. Alcohol, drugs and smoking are very dangerous on these days of pregnancy.
From the thirteenth week begins the final period of internal development – fetal or fetal. At this time, the fetus is already moving, but the woman still does not notice these movements. Usually, the mother begins to feel the movement of the child from the sixteenth to the twentieth week. True, during both pregnancies, I felt the movements of my daughters at exactly fifteen weeks.
At seventeen weeks the fetus appears initial sucking movements, the baby opens and closes the mouth.
By the fifth week of pregnancy, the doctor begins to hear the heartbeat of the baby.
At the end of the twenty-fourth week of pregnancy, the baby is already so formed that during premature birth it can survive in special conditions.
In the future, it is not the development, but the maturation of the child. After the birth, the doctors told me about the eldest daughter that she was born full-term but immature. Maturation after birth is slow: each week of prematurity turns over years.