The fertilized egg divides many times to form a cell mass, which gradually grows and begins to differentiate. One part becomes the fetus, and the other part becomes the accessory organ that supplies nutrition and protects the fetus. This is the first week of life.
In the second week, the little life grows very fast and the spine is formed. Brain tissue, spinal cord, nervous system and eyes all have certain prototypes. At the other end of the spine is a small tail. Blood vessels are beginning to form at this point, and the heart is not yet formed, but where the heart is formed there is a heartbeat.
The heart appears in the fourth week, and the limbs appear in the next week. Eyes and ears follow, and lungs and liver begin to take shape. The weight of the human brain increases rapidly, significantly faster than that of other animals.
In the seventh week of the embryo, fingers and toes begin to appear on the hands and feet, and the eyes are clearly visible. The embryo begins to straighten and move in the amniotic fluid. The overall appearance is similar to that of a child, and the tail disappears. By the end of the eighth week, the embryo has grown nearly 3 centimeters and all its organs have begun to take shape. The coming months will only see incremental improvements.
When a baby enters its third month (8 to 11 weeks), it is called a fetus. By the 8th week, the newborn head accounts for 1/2 of the total length of the fetus. After that, the growth accelerates, and the weight doubles by the end of the 12th week. The visceral system comes into play, allowing amniotic fluid to be swallowed and excreted as urine. In the ninth week, the vulva of male and female fetuses are roughly similar. By the end of the twelfth week, the male and female vulvas of mature fetuses have appeared.
In the fourth month (12-15 weeks), the fetus has reached 16 centimeters in length, weighs about 120 grams, and is growing rapidly. The proportion gap between the fetus\’ head and body is small, the legs are relatively elongated, and the bones are ossifying rapidly. Under the action of the liver, stomach, and intestines, green meconium is formed, which can only be excreted after birth. Lanugo appears on the skin. The heart rate is twice that of an adult.
In the fifth month (16-19 weeks), pregnant women will feel the fetus in the abdomen kicking themselves to indicate its presence. This is fetal movement. Another piece of information about the fetus is that the fetal heartbeat can be heard in the abdomen, which is usually 120-160 beats per minute. The fetus already has hearing and can hear sounds, so prenatal education can begin. At this time, the fetus is about 25 cm long and weighs 500 grams.
In the sixth month (20-23 weeks), the fetus is about 30 cm long and weighs 660 grams. Bend your arms in front of your chest and lift your knees to your abdomen. Those born at this time often only survive a few hours because their respiratory systems are not fully developed.
In the seventh month (2427 weeks), the fetus is about 35 centimeters long and weighs about 1,000 grams. Looks like a little old man. Although the baby at this time can have superficial breathing and crying, it is still difficult to survive.
In the eighth month (28-31 weeks), the fetus is about 40 centimeters long and weighs about 1,700 grams. The fetus moves freely in the womb, its movements are coordinated, and its position is basically fixed, usually head down. The nervous system is further improved, and the lungs and other internal organsBasic development. Premature babies born at this time can survive if they are carefully cared for in an incubator.
In the ninth month (weekend 32-35), the fetus is about 45 centimeters in length and can gain 1,000 grams in weight within 4 weeks, and its development is basically completed. If premature babies born at this time receive careful care, their survival rate can reach over 90%.
In the tenth month (36-40 weeks), the fetus is fully developed, with a length of about 50 cm and a weight of about 3,000 grams. The skin is white with a hint of pink, and there is a layer of white fat on the body surface. The breasts are well developed, the breasts are protruding, and the baby can burp and suck his thumb. The male testicles are usually located within the scrotum.
Although childbirth takes several hours to a day or even longer, the fetus has to endure a huge test. A well-developed fetus can withstand tests such as hypoxia and squeezing and deliver smoothly. Children born normally have a longer delivery time than children born by cesarean section, but their ability to adapt to the outside world is stronger than children born by cesarean section.