Intrauterine growth is a fundamental stage of life since many factors at this time can condition all future growth. The growth of the baby in the womb It comprises two periods: embryogenic and fetal growth.
The growth and development of the future baby are characterized by an increase in size, increasing structural complexity and maturation of functions. How can we know if it is growing properly in the uterus?
We know that through ultrasound during pregnancy the approximate weight of the baby is estimated based on the measurements of three parameters: the abdominal circumference, the perimeter of the head and the length of the femur.
In addition, based on averages, there are calendars to know weight and measures during pregnancy and formulas to calculate fetal weight according to the week of gestation.
Thanks to these estimates and measurements through ultrasound we can know if the fetus develops according to its gestational age, or if it will be more or less large, that is, to know more about the baby growth in the womb, in its different stages, about what we tell you in detail below.
Embryo development
Recall that embryogenesis is the complex generative process that leads to the formation of a multicellular, plant or animal organism, from the zygote.
Human embryogenesis It is defined as the process that begins after the fertilization of gametes to give rise to the embryo, in the early stages of development of multicellular living beings. In humans, this process lasts about eight weeks, at which point the product of conception ends its first stage of development and becomes known as a fetus.
As of the fourth week, the embryo begins to develop the vestiges of future organs and devices, and at this stage it is very sensitive. A phase of frantic growth begins that lasts another month, during which all the organs, systems and devices of the future adult organism are outlined.
During the embryonic development period the different organs of the future fetus are formed and is characterized by an increase in the number of cells (it grows almost exclusively by hyperplasia, that is, the increase in size of an organ or tissue because its cells have increased in number) .
The growth of the fetus
In the period of fetal growth there is an intermediate phase of hyperplasia and hypertrophy, with increased cell size and decreased mitotic index or cell division. Hypertrophy is the increase in the size of an organ when it is due to the correlative increase in the size of the cells that form it (the organ has major cells, and not new). It is distinguished from hyperplasia, in which case an organ grows by increasing the number of cells, not by a larger size of them.
The growth curve is characterized by a progressive increase in the speed of growth in length, which reaches its maximum at approximately week 18, while the maximum increase in weight takes place towards the final weeks of pregnancy.
In the final stretch of pregnancy the baby grows at an accelerated pace, gaining weight between 200 and 300 grams per week. In the last stage of pregnancy there are already organs and tissues formed, and there is an accumulation of fat under the delicate skin, which will help you better regulate your body temperature when you are born.
At the beginning of the week 35 weighs about 2,400 kilos and measures 47 cm, although at this height there can be a large difference in size between different babies. In week 38 the estimated measurements of the baby are 50 centimeters and 3,200 kilos. In week 40 the baby measures 52 centimeters from the head to the feet and weighs about 3'400 kilos.
Of course, these are approximate average measurements, and it won't be until it is born when we know how much the baby is. Even the latest ultrasounds that estimate the fetus's measurements can be wrong.
What fetal growth depends on
Fetal growth is a very organized process in which, as we have seen, complex changes are coordinated and modifications at the molecular and cellular levels are integrated to allow the development of the entire organism. Any adverse influence on this process can have negative consequences. The delay or alteration in growth will depend on the nature, timing, duration and intensity of the disturbance.
Adequate fetal growth It depends on an optimal interaction between different factors:
- Fetal factors: the ability of the fetus to use the nutrients it receives. The most important is the genetic provision of the fetus. Insulin and insulin-like growth factors play an important role in this phase of growth. 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.
- Placental: 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.
- Maternal factors: logically the mother is the natural center and source of the immediate principles and oxygen essential for the correct fetal growth. The nutritional status of the mother influences. 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, related to the above: environmental factors that may depend on the mother (kidney disease, hypertension, heart disease, cholestasia, drug use, excess alcohol, urinary infections ...), the fetus (genetic, chromosomal abnormalities, infections) or placental (aging, heart attacks and placental insufficiency).
The current devices allow to measure the embryo, head, bones, limbs, blood vessels, kidneys ... of the fetus and estimate its weight, seeing if baby growth in the womb It's appropriate. But the baby's length cannot be measured because the fetus is shrunken in the womb and will only be fully stretched when it is born.
Photos | molly_darling, seamusiv and WomEOS 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?
