Every pregnant woman wants to know what is happening in her body, how her baby grows and develops, whether there are any dangers on his way. This is provided by a monthly prenatal visits to the doctor and various fetal development diagnostic studies. Ultrasonography is the most informative method of investigation that sought to identify abnormal fetal growth.
Fetus and its relationship with the mother’s body
Fetus is a growing organism, beginning with the ninth week of fetal development until birth. Before the ninth week this organism is called a fetus or embryo. A normal pregnancy lasts 40 weeks plus or minus two weeks. Gynecologists divide these 40 weeks into three terms: I trimester – up to 12 weeks, II – 12-24 weeks, III – from 24 weeks before birth.
Fetus is inextricably linked to the mother’s body, throughout pregnancy there is a system of mother – placenta – fetus operating. Mother’s body provides optimal conditions for fetal development. Mother and fetus collaboration involves nervous, endocrine, immune and other mechanisms. Mother’s body and fetus begin interacting most fully after placenta development, which allows fetus adapting to changing conditions in maternal organism.
Fetal development in the first trimester of pregnancy (up to 12 weeks)
In the end of the fourth week of pregnancy an embryo is implanted in uterus mucous membrane, where primordia of organs and membranes is formed. In the end of the eighth week of pregnancy length of an embryo reaches approximately 3 cm, it is already possible to distinguish head, torso (it is equal to the length of head), rudiments of limbs, eyes, nose, mouth. Microscopic structure of sex glands allows determining sex of the fetus.
In the end of the 12th week fetus reaches a length of 9 cm, weight – 40 g. Limbs are clearly defined, formation of external genitalia begins, x-rays allow seeing the points of ossification in a cartilage skeleton.
Fetal development in the second trimester (12-24 weeks)
During 16th week, the length of fetus reaches about 16 cm, weight – approximately 120 g, sex is clearly visible, skin is thin, smooth, reddish, without subcutaneous fat, face is almost formed, ossification of skull begins. In connection with formation of muscular system, activity of limb movement is growing, there are weak respiratory movements.
In the end of the 20th week fetus reaches a length of 25 cm, weight – 300 g. Movement is so active that mother feels them, and fetal heartbeat can be heard. Skin of fetus, starting with head and face is covered with prenatal hairs and entire body – eldest lubricant, consisting of a mixture of fat-like secretion of sebaceous glands with scales of skin surface layer. The first cal – meconium is formed in the gut. Subcutaneous tissue is formed in the lower abdomen.
In the end of 24th week the length of fetus is 30 cm, weight – 700 g. The internal organs are so mature that sometimes, under appropriate conditions, fetus may be viable for premature birth.
Fetal development in the third trimester of pregnancy (from 24 weeks until birth)
By the 30th week, the length of fetus is about 35 cm, weight – about 1 kg. Fetus looks like an «old man» because of poor development of subcutaneous fat, whole body is covered with prenatal hairs, ears are very soft, nails do not reach fingertips. In girls, large labia do not close small, boys’ testicles are not descended into the scrotum, navel is located closer to the pubis. Fetus is premature and unripe, that is unsustainable, as functions of its internal organs and systems are not perfect. After birth, survival of such fetus is small and is possible only under especially favorable conditions.
On the 34th week fetus has a length of about 40 cm, weight – about 1,6 kg. Fetus is viable, but requires special care conditions.
On 38-40th weeks fetus acquires the characteristics of maturity: its length is 45 cm, weight – about 2,5 kg. «An old man» look is lost due developed subcutaneous tissue, skin becomes pink, navel is located in the usual place. Fetus becomes fully viable.
Fetal development. Signs of fetus maturity
Full-term fetus under adverse conditions of intrauterine development may have signs of immaturity and vice versa, aborted fetus may be born mature, so the concept of preterm and maturity do not always coincide.
Fetal length is an important sign of maturity: not less than 47 cm; and weight should be not less than 2,5 kg. Signs of maturity also include navel position: it should be positioned midway between the sternum and the pubis. Other important factors: state of skin (pink), lack of «senile» atrophy, development of subcutaneous fat, presence of prenatal hairs only on shoulders and upper back, hair condition of hair, nails and other symptoms.
With a weight of 4 to 5 kg fetus is consirered large, more than 5 kg – giant. Weight increase may be associated with features of mother’s nutrition, hereditary factors, number of births, mother’s illness (for example, diabetes often causes a large fetus), etc. A newborn, which has great weight must be carefully examined to avoid possible diseases.
Balanced diet, locomotor activity, continuous monitoring of fetal condition by a women’s clinic doctor are a guarantee of a full-term healthy baby birth.
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