The first home of every person - the womb of the mother - is almost always hospitable and comfortable. Nevertheless, 38 weeks (about 266 days) between conception and birth pose a greater threat to life, especially for the first 8 weeks than any other throughout the rest of the life up to the ninth decade. But, despite the potential risk, most children are in this world completely healthy and timely.
Traditionally, doctors divide intrauterine development into three consecutive stages - the trimester:
- 1st lasts up to 12 weeks;
- 2nd - from 12 to 28 weeks;
- 3rd - from 28 weeks until the birth of the child.
Biologists and embryologists, in turn, prefer to divide intrauterine development into 3 unequal periods of time: embryonic, embryonic and fetal.
We all begin our journey as inanimate matter in the form of two merged cells containing 46 chromosomes, which, in turn, carry an unimaginably vast amount of information about this new emerging life. It is curious that in China it is customary to consider the day of conception as the birthday, and not the birth of a child. This tradition, it is worth noting, significantly affects the number of abortions.
Intrauterine development of the child by week :
0-2 weeks. The first division of a fertilized egg begins 24-36 hours after fertilization. During the first 40 hours after the first division, all cells are still the same. 3-4-day-old zygote consists of 12-16 cells and is called morula, its size is approximately equal to the pin head. After 4 days, the dividing cells begin to differentiate and are divided into two germ layers: the outer one forms the protective membrane around the embryo - the future placenta, and the embryo itself will form from the inner one. Further development occurs in the fallopian tube, resulting in the formation of a blastocyst. Then it approaches the uterus, enters its cavity and attaches to the endometrial wall of the uterus - this process is called implantation. It occurs within 10-14 days from the moment of conception. At this stage, the embryonic ends and embryonic intrauterine development begins. About 60% of blastocysts do not attach to the uterine wall and, therefore, do not survive to the embryonic period. Most of them have gross developmental disabilities. Thus, nature does not allow the birth of non-viable individuals.
3-8 weeks. The period of embryonic development begins. At this stage, the synthesis of various chemicals that inhibit the mother’s immunity takes place in order to prevent the rejection of the tissues of the unborn child as a foreign body in the uterus. In addition, the hormone chorionic gonadotropin is actively synthesized (on the basis of which pregnancy is diagnosed) - it stops the woman's menstrual cycle. The metabolic rate also increases (by 10-25%), respiration, and blood circulation. Starting from 3 weeks of development, the unborn child is in a very sensitive period of growth. The first trimester of development is the period of morphogenesis, when all human tissues and organs are laid. Scientists say that this period is the most perfect and debugged mechanism that you can imagine! Even the design and launch of space satellites involving thousands of people and electronic devices is not as complex a process as intrauterine development!
At this stage, there are many spontaneous abortions associated with the presence of gross chromosomal defects. Also, a high probability of miscarriage due to inappropriate conditions in the uterus of a woman. Only 1 out of 6 embryos survives up to 8 weeks. During this period, the embryo is most sensitive to harmful influences from the outside, so a woman should be very careful and avoid taking medications, drinking alcohol, and smoking.
At the end of this period, it is almost impossible to influence the morphology of the child.
At 3 weeks, the size of the embryo exceeds the original by 10 thousand times.
At the 3rd week of development, a neural tube is formed - a prototype of the brain and spinal cord, the umbilical cord and placenta develop.
Week 4 - a heart is laid. By the end of 4 weeks, it begins to beat separately from the mother. The eyes begin to form. The neural tube closes. The growth rate of the embryo is about 1 mm per day.
Week 5 - you can already see the arms and legs of the unborn child.
6 week - genitals begin to form. In case of failures at this stage, it is possible to form a person with signs of both sexes. At this time, the embryo is already visible on an ultrasound scan.
At week 7, the formation of facial defects such as cleft palate is possible . A skeleton is formed.
By the 8th week , the process of forming the main organs is completed. The rapid development of the brain begins.
Starting from week 9 , the beginning of the last fetal period of development is marked. From the 13th week, the obstetric second trimester of pregnancy begins. At this time, the child looks the same as the newborn, only smaller. Although the head is still disproportionately large. The body straightens and lengthens. The future mother notes a surge of energy. Despite the potential dangers, further development, as a rule, is successful. At this stage, the brain begins to function.
At later dates, fundamental changes no longer occur: the fetus grows in size, its organs improve, by the 16th week the mother already senses its movements, by the 20th week the hair begins to grow.
By the 7th month, the fetus can already breathe on its own, digest food, the excretory system is fully functioning . In the event of premature birth, the baby can already live on its own.
It is proved that in the last 3 months of its intrauterine development, the child can already react to the outside world. He actively moves, hiccups, cries. The main senses are developed: smell, touch, taste, eyesight, hearing. From the 16th week of development, the child reacts to sound (distinguishes voices), light.
As a result, by day 266, the child finally takes the position head down and is ready for the birth.
In only 5% of cases, spontaneous fading of the fetus in late periods (after 22 weeks) is noted.
The intrauterine development of the fetus by week is extremely important information: for the mother - to understand the processes in her own body and the risks associated with them, for doctors - to monitor the development of the fetus, and for the whole society as a whole to understand what is already from the moment Conception begins a rapid and incredibly complex process of forming a new life, rather than primitive biomass.