The prenatal development is the period of the fastest and most complex growth of a fetus. In only 40 weeks, about 280 days, only one egg cell develops into an organism with all morphological and physiological human features. In medical literature, prenatal development has three stages: germinal, embryonic and fetal stage.
The germinal stage of prenatal development
This first stage begins with the binding of the male and female sex cells, i.e. forming an egg cell, called zygote. The zygote will divide into two cells, then this two will divide into four, and so on. So, this stage is actually the period of the zygote reproduction. It will divide into hundreds of cells. From these cells will be created a baby, placenta and amniotic fluid.
The germinal stage lasts for about two weeks until the zygote binds to the uterine wall breaking through the fallopian tube. The period of that journey is crucial for continuing pregnancy. If the zygote arrives before or later in the uterus, the uterus will not have the conditions provided for its development and will be ejected from the body.
The embryonic stage of prenatal development
When the zygote binds to the uterine wall, the next stage begins. The embryonic stage lasts from 2 to 8 weeks of pregnancy, i.e. about 6 weeks. During this period, amniotic fluid, placenta and all basic organs of the future child must be formed.
Amniotic fluid protects the embryo’s weak muscles and soft bones from rough surfaces and strokes during the mother’s movement. The amniotic fluid provides an environment in which the embryo can float and change its position safely.
The mother’s and embryo’s tissue create placenta together. The umbilical cord connects the embryo and placenta. Placenta prevents direct contact between the blood of the mother and the embryo. It allows the nutritional elements and oxidases from mother’s blood to come to the embryo. Also, placenta allows absorption of the embryonic body toxins into the mother’s blood, from where will be ejected through the urinary and digestive system.
Development of an embryo
In this period, the embryo’s cells are clearly divided into three layers: exoderm, endoderm and mesoderm. The ectoderm develops into a nervous system, sensory system, exterior parts of the skin, hair and teeth. Muscle, skeleton, vascular system, heart, excretory system and internal parts of the skin develop from the mesoderm. Endoderm develops into a system for digestion, breathing and all other vital organs.
Embryonic organs develop at incredible speed. The development goes from the head to the bottom and from the middle to the periphery of the embryo. For example, first hands develop, then the legs or spinal cord develop in front of the arm, and so on.
Certainly, after the formation of basic organs, the embryo becomes capable of responses to the environment. Studies on embryos taken from women after abortion show that the embryo turns the head and neck and opens mouth on touch in the area of its lips. However, mothers can’t feel embryos in the uterus yet, because it’s still extremely small.
The fetal stage of prenatal development
This stage lasts from 9 weeks pregnancy to childbirth. During this stage, the fetus becomes 10 times larger and its organs become more complex and functional.
Prenatal development from 9 weeks to 6 months of pregnancy
Already in the 10th week, a fetus reacts by squeezing its fingers on the subtle stimulation of its palm. Over the next week, fetal movements are becoming more and more complex. Now, it can slowly bend the body.
By the end of the fourth month, when the fetus becomes bigger, mothers begin to feel its movements. Also, the fetus is beginning to look like human beings. The body begins to grow in relation to its head. Eyes get their final shape. Hair begins to grow. Also, the doctors can affirm a sex of a fetus from the beginning of the third month of pregnancy.
At the end of the 4th month, the blood is created in the marrowbone and most bones and joints have already been developed. There is also a visible division between the right and left hemispheres of the brain.
Fetal movements become weaker at 16 and 17 weeks of pregnancy, but after 6 months, the fetus becomes movable again. It starts moving extremities, changing position, sucking a thumb, …
At the end of the 5th month, fatty tissue is formed which should provide heat to the newborn.
Prenatal development from the 6th month of pregnancy to the childbirth
At the end of the 6th month, the lungs of a fetus began to create a chemical substance which prevents its collapse. Clinical practice confirms that a fetus can already survive outside the mother’s womb, even if its weight is below 700 grammes. But, in such case, its further development is uncertain.
At the end of the 7th month, the lungs become capable of breathing and the nervous system become able to manage the rhythmic breathing movements. In the same month, the fetus’ eyes begin to open and react to the light.
In the 8th month, the more fat tissue is forming making a skin smoother. At the end of the 8th month, the skin of the fetus is completely smooth, and the legs and arms become bumpy.
In the 9th month, the fetus becomes all chubby, gaining 50% of its weight. However, in the last month, growth is slowing down. The brain becomes much more developed and the fetus becomes completely physically and mentally prepared to live out of the womb.
After all, we can conclude that prenatal development follows a particular pattern. Many scientists consider that genes determine prenatal development. On the other side, religion believes that God determines this pattern. Certainly, there isn’t any proof of what determines the prenatal development. Regardless of how many scientific data we have, the prenatal development is a great mystery. It is the mystery of life, a mystery of creation, birth and survival.