Fetogenesis refers to the biological development of the fetus. Fetogenesis directly follows embryogenesis and begins around the ninth week of pregnancy. Fetogenesis ends with birth in the ninth month of pregnancy.
What is fetogenesis?
Fetogenesis is the term used to describe the biological development of the fetus. Fetogenesis directly follows embryogenesis and begins around the ninth week of pregnancy. Fetogenesis is a branch of embryology and includes the further development of the organs that are created during embryogenesis. A distinction is made between early (61st to 180th day) and later fetogenesis (181st day to the day of birth). Growth is faster during the period of fetogenesis than at embryogenesis. The risk of organ malformations, miscarriages and malformations decreases with the onset of fetogenesis. Disorders during this period are usually manifested by short stature or malformations of the extremities.
Function and task
Fetogenesis begins around the third month of pregnancy with changes in facial proportions. The eyes and ears migrate to their eventual position. In addition, arms and legs lengthen and the fetus is able to move its first muscles. However, these small muscle movements are usually not yet noticeable to the mother. Twelve weeks after fertilization, the sex of the unborn child is then apparent. In the third month of pregnancy, the child can even already taste. The fourth and fifth months of pregnancy are characterized by strong longitudinal growth. So-called woolly hairs form on the surface of the body. This type of hair is also called vellus hair. The vellus hairs cover many areas of the skin and are not replaced by stronger terminal hairs until the onset of puberty. In the fourth month, the sebaceous glands of the skin are also activated and the child’s first heart sounds become audible. Now the mother can usually also perceive her child’s movements. In the sixth month of fetogenesis, the focus is on skin growth. At this time, the fetus appears wrinkled and wrinkled because, although the skin is growing, the underlying layer of fat is not growing as quickly. In the sixth month, the unborn baby continues to grow steadily. The spiral twist of the fifty-centimeter-long umbilical cord allows the child a large range of motion. The sense of balance and the propriovestibular system also develop now. The fetus is now able to perceive its position in space and the position of individual body parts in relation to each other. In the seventh month of child development, the fetus’ lungs become functional. Other vital organs are also completed. For this reason, prematurely born children are usually viable from the 28th week of pregnancy. Since all vital organs are now created and usually also completed, the growth of the unborn child is now even more clearly in the foreground. In the eighth month, fat increasingly forms in the subcutaneous tissue. The previously wrinkled and wrinkled skin now tightens. In addition to normal fat, brown adipose tissue is also formed in the shoulder area. Brown fatty tissue has the property that it can be quickly converted into heat energy by the body. With the help of the brown fatty tissue, the newborn regulates its heat balance. In addition, in the eighth month, the child is no longer only able to taste, but can also smell thanks to the maturation of the sense of smell. The liver grows a lot at this time and starts storing iron. In the last month before birth, the fetus sinks deeper into the mother’s pelvis and remains there in the later birth position. Birth then occurs about forty weeks after the onset of the last menstrual period.
Diseases and ailments
During fetogenesis, growth disorders may occur in the unborn baby. These disorders may be genetic or acquired, for example, through infection. Genetic causes of growth disorders include chromosomal abnormalities and genetic defects. A well-known chromosomal abnormality is trisomy 21. A characteristic symptom of trisomy 21 is short stature combined with a short neck and a slightly smaller, round head, with a flattened occiput. Another chromosomal abnormality that leads to disorders in fetogenesis is Turner syndrome. This also results in short stature, among other things. Infections of the mother can pass to the child and negatively influence fetogenesis.Above all, an illness of the mother with rubella, toxoplasmosis, syphilis and cytomegaly poses a risk for child development. Not only infections or genetic defects can disrupt the development of the child in the womb. Alcohol consumption by the mother during pregnancy can cause lifelong impairments for the child. Symptoms associated with the mother’s alcohol consumption during pregnancy are grouped together under the term fetal alcohol syndrome. Alcohol acts as a cellular toxin in the fetus and results in numerous different cellular damages. Cells may enlarge, shrink or die. Children with fetal alcohol syndrome are smaller and lighter than children of the same age. In particular, the muscles and fatty tissue are poorly developed. Facial malformations, low-set ears and eye changes can also be observed. Cognitive and emotional disorders also occur. Furthermore, perception, speech and motor skills are impaired in affected children. Many mental and developmental deficits resulting from fetogenesis can be compensated for by the affected children as they grow up. This is not usually true for physical malformations.
