From the moment of conception, a new being goes through two important stages: the embryonic period and the fetal period. Is considered embryo from the union of the ovum and the sperm until the eighth week of gestation and fetus from the ninth week to the time of birth.
The embryo that begins with the union of two cells begins a replication phase to create the primordial structures that provide the final form of the living being and that are specific to each species, these by the end of the embryonic period already begin to have specific functions .
In the case of humans, at the end of the eighth week of gestation this process has already been concluded and it is from the ninth week when the embryo is called a fetus, at this time all the structures that must develop have already been formed and grow up to the moment of birth.
Fetal development
Third month. The fetus measures on average about 7.5 cm; In this phase, the ossification processes of the bones and the development of the teeth as well as some cartilage such as the nails begin, at the end of this period the genitals begin to develop. The liver makes the baby's red blood cells.
Fourth month. The formation of the arms and legs ends, the fetus begins to have mobility, the liver and pancreas also develop, beginning to produce secretions such as bile. At this stage it is already possible to know the sex of the baby.
Fifth month. It measures about 25 cm, the hairs begin to develop; in this phase the mother can already begin to feel the baby's movements.
Sixth month. The eyebrows and eyelashes are identified, the sense organs have already developed, the process of lung development begins.
Seventh month. The structures of the nervous system develop to begin to control the various functions of the body.
Eighth month. The development of fat deposits and subcutaneous tissue begins, the fetus begins to have respiratory movements but even its lungs are not fully formed.
Ninth month. It reaches 50 cm and is fully formed, in addition it already has defined sleep patterns, in this last month the fetus gains weight and the maturation of the lungs culminates, between weeks 38 and 40 it is ready to be born.
Estimation of fetal age
The use of ultrasound has made it possible to better monitor the evolution of the fetus, as well as to better specify the exact time of pregnancy, which is estimated based on well-established parameters such as the length of the femur, length of the head to the coccyx, head circumference, and fetal weight.
Factors influencing fetal development
The most critical phase of gestation is embryonic development since at that time is when more damage can be caused by the effect of external factors.
During the fetal stage it is also possible that alterations are presented if there is exposure to factors such as poor diet of the mother, nutrient deficiency, chronic diseases such as diabetes or high blood pressure, infections during pregnancy, exposure to toxic agents, use of illicit drugs, alcohol consumption, habits such as cigarette smoking and the use of medications.
All these factors are capable of altering the development of the fetus and giving rise to malformations or congenital anomalies, many of them capable of producing permanent disability or incapacity. Adequate prenatal control is capable of preventing these conditions and applying corrective measures when they have already occurred.
