The prenatal and fetal development of a child

The conception and subsequent prenatal development of a child is an incredibly exciting and at the same time extremely complex process. While most people still know that due to exciting activities it comes afterwards to a fertilization of the egg cell, it becomes already more difficult with the following development steps. Mainly, of course, you deal with the development of the child from the beginning of birth.

Nevertheless, in this article I would like to talk about prenatal, that is, about the prenatal development of a child.

Zygote stage

The zygote stage is the first developmental step in a child’s life and begins immediately after the sperm and egg combine, where the father’s 23 chromosomes combine with the mother’s 23 chromosomes. This gives the 46 chromosomes that every human has. One of the main reasons for infertility as well as the occurrence of miscarriages is due to the fact that about 10-20% of embryos have a defective chromosome number and are therefore not viable. Therefore, the zygote stage is already the first critical developmental stage of an embryo.

During this stage, the fertilized egg (zygote) migrates into the uterine wall. This process takes place in the first 2 weeks.

Embryonic stage

After the zygote stage has been completed, the so-called embryonic stage now occurs in the 3-8 week of development. Developmental mechanisms such as cell division, specialization, migration and cell death already begin here. These are used to differentiate the organ system. This is because, on the one hand, the rapid division of cells implements an expansion of what has existed up to now. During cell migration, the previously unspecific cells migrate to their later destination. There, in turn, cell specialization sets in, which remodels the embryonic stem cells to produce cells with characteristic properties and functions. Targeted cell death is used to remove troublesome cells or cells that are no longer necessary, for example, to shape the toes of the foot.

These cell development mechanisms form a symbiosis without which the complex organism of a human being could not be constructed.

Likewise, the placenta develops to supply oxygen to the child. This has a semipermeable membrane (semipermeable) and thus establishes the exchange of oxygen between two blood circuits, namely those of the mother and the child. There is no direct contact between the two blood circuits. On the one hand, this membrane allows oxygen and nutrients to pass through. On the other hand, it holds back some hazards such as possible pathogens or toxic substances, but not all.

In turn, a connection between the placenta and the embryo occurs through the umbilical cord, which provides a blood supply/oxygen supply. The amniotic sac, filled with amniotic fluid, protects the embryo from excessive shocks, movements and fluctuations in temperature. By the way, the amniotic fluid is produced by the innermost egg membrane of the amniotic sac and is a clear liquid.

All these systems (umbilical cord, amniotic sac, placenta) are called support system.

Fetal stage

From the 9th week of pregnancy until birth, the fetal stage takes place. During this time, the organism develops to such an extent that viability after birth is given. During this stage, the senses also continue to develop so that the fetus can absorb information.

Month of lifeSize of the fetusBehavior of the fetus
3.2 cmFirst reflexes, brain takes over impulse control, grasping, swallowing, sucking
4.9 cmTurning the head, movement of the extremities, opening and closing the mouth, blinking, frowning, sucking the thumb, individual behavior
5.16 cmStronger movements, which can be felt by the mother
6.25 cmPremature babies are survivors, special sleep and wake phases, individual sleep positions, reaction to sounds and changes in movement and pulse rate
7.30 cmIrregular breathing movements, hiccups, movement of the eyes, triggerable grasping reflex.
8.35 cmIndependent survival after birth possible under higher risk of infection and more difficult temperature regulation, habituation
9.45 cmHigh activity in the womb, independent survival possible after birth
Fetal developmental stages

Factors influencing prenatal development

Nowadays it is undisputed that there are harmful factors influencing the development of an unborn human being. In technical terminology, these are called teratogens. These include, in particular, alcohol, smoking, medications, environmental toxins, radiation damage, and infectious diseases. Smoking also increases the risk of sudden infant death syndrome, for example.

During the embryonic period, mainly structural changes (malformations) occur. However, with the onset of the fetal period, functional or psychological changes in the organism come to the fore.

As you can see, prenatal development is a very exciting and important field. The next article then follows with the birth as well as the postnatal development within the first twelve months.


Suggested Citation

Götz, S. (2021). Prenatal and fetal child development. Development step by step. ISSN: 2748-2979. Accessed 12.06.2021. Available at:

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