We have already told in detail how the baby is growing in the womb, and now we want to focus on the factors that influence fetal growth, that is, those that determine the greater or lesser growth of the baby before birth.
Fetal growth is a complex process in which molecular and cellular modifications are combined and integrated to allow the development of the entire organism. If there is any adverse influence on this process, there may be negative consequences on development.
The delay or alteration in growth It will depend on the nature, timing, duration and intensity of the disturbance. Restricted intrauterine growth is the expression used to define a baby that is smaller than normal during pregnancy due to a problem: babies do not grow inside the uterus at the speed they should and usually have more weight Low at birth
Schematically, fetal growth is controlled by placental, fetal and maternal factors; It is inseparable from placental growth and requires a continuous supply of nutrients and adapted to each period of pregnancy. More broadly, adequate fetal growth It depends on an optimal interaction between the following factors:
Fetal growth factors
Fetal factors: is the ability of the fetus to use the nutrients it receives. There are two factors related to the development of the fetus: hormones of fetal origin and, more importantly, genetic factors or the genetic provision of the fetus.
Within the hormones, the most important is insulin, responsible for growth after the 26th week of gestation. Insulin stimulates cellular uptake of amino acids, protein synthesis and fat and glycogen deposits in the liver, heart, muscle tissue and subcutaneous tissue. Fetal insulin levels are related to maternal and fetal glucose levels. Insulin and insulin-like growth factors play an important role in this phase of growth. Type 2 insulin growth factor, IGF-2 is a single-chain peptide hormone similar in structure to insulin, with an important role in fetal growth.
Genetic factors of the fetus are responsible for about 15% of variations in birth weight, being significantly less important than maternal factors. Child growth and adult size are genetically determined by parents. In fetal growth, maternal genes become more important than paternal ones. There are some chromosomal pathologies associated with delayed uterine growth (trisomies 21, 18 and 13) and abnormalities of sex chromosomes (Turner syndrome).
Placental factors
The most common cause is a problem in the functioning of the placenta, which is the tissue that carries food and oxygen to the baby. the placenta will be the modulator of the factors that will determine the degree of fetal development: it provides nutrients and oxygen, regulates the diffusion in the maternal circulation of fetal metabolism products, acts as an endocrine organ producing hormones (placental lactogen), growth factors, neuropeptides and cytokines.
Its smooth operation, focused on the placental flow, is related to the factors that we explain below. For example, placental flow is reduced in pathologies that produce vasoconstriction of the uteroplacental, such as hypertensive syndromes.
Changes in the area of the hairy surface are also influenced, partially related to maternal nutritional status. The processes that affect the uterus-placental and placental-fetal circulation reduce the amount of nutrients available to the fetus.
Maternal Fetal Growth Factors
Logically, the mother is the natural center and source of the immediate principles and oxygen essential for proper fetal growth. The mother's nutritional status influences, but although maternal nutritional factors are one of the main determinants of fetal growth in undernourished populations, women in good nutritional status have a minor effect.
Non-nutritional factors of the mother seem to explain 20% to 50% of the variation in birth weight. Maternal somatomedin (insulin growth factor type I or IGF-I), if it is producing abnormal amounts of growth hormone, would be associated with birth weight.
Maternal vascular involvement, conditioning a decrease in uterine-placental flow can cause up to 25-30% of cases of intrauterine growth retardation. Remember that smoking during pregnancy It affects the growth of the baby, since the blood supply to the placenta decreases for 15 minutes, increasing the heart rate. Inhaled carbon monoxide causes the fetus to receive 40% less oxygen.
Environmental factors
These factors are related to the previous ones: the environmental factors that can influence the mother (nephropathy, hypertension, heart disease, cholestasia, drug use, excess alcohol, urinary infections ...), in the fetus (causing genetic, chromosomal abnormalities, infections) or placental (aging, heart attacks and placental insufficiency).
Other fetal growth factors
There are other factors that may explain a delay in uterine growth, such as a congenital infection (responsible for 5% of delays) or a multiple pregnancy, although in this case the higher risk is conditioned by the higher incidence of pregnancy-induced hypertension, higher incidence of congenital malformations, feto-fetal transfusion syndrome, and by the maternal inability to meet the nutritional requirements generated by multiple gestation. .
Although genetic alterations, malformations, infections of the mother during pregnancy, consumption of tobacco or drugs and high blood pressure before or during pregnancy can also affect the growth of the baby, the most frequent factor of uterine growth retardation is complications in the placenta
If the genetic information is adequate and the environment conducive would be the optimal conditions to obtain growth and development according to the family genetic potential.
But as we see there are also factors that influence fetal growth on which we can influence, and lead a healthy lifestyle before and during pregnancy will help the baby to develop properly.
Photos | .: elNico :. and QuinnDombrowski on Flickr In Babies and more | What is pregnancy? The size of the gut does not depend on the size of the baby, delayed intrauterine growth, how much will you grow when you grow up? How tall is the fetus?
