The prenatal development stages are a time of remarkable change that helps set the stage for futurepsychologicaldevelopment.
At a Glance
The three prenatal development stages involve the processes that occur from conception to birth.
Keep reading to learn more about the events that take place during each of these stages of prenatal development.
Illustration by Katie Kerpel. © Verywell, 2017.
The fertilized egg is called a zygote.
Important Events:
Cell Division
Cell division begins approximately 24 to 36 hours after conception.
The cells develop into what is known as a blastocyst.
The blastocyst is made up of three layers, each of which develops into different structures in the body.
Implantation takes place if the cells nestle into the uterine lining and rupture tiny blood vessels.
However, it is important to recognize that implantation is not always an automatic and sure-fire process.
Approximately four weeks after conception, the neural tube forms.
This tube will later develop into the central nervous system, including the spinal cord and brain.
The neural tube begins to form along with an area known as the neural plate.
Over the next few days, more ridges form and fold inward until a hollow tube is formed.
The blood vessel that will become the heart starts to pulse.
During the fifth week, buds that will form the arms and legs appear.
At this point, the embryo weighs just one gram and is about one inch long.
At this point, the basic structure of theperipheral nervous systemis also defined.
As neurons form, they migrate to different areas of the brain.
The fetal period of prenatal develop marks more important changes in the brain.
This period of development begins during the ninth week and lasts until birth.
This stage is marked by amazing change and growth.
Nervous System Develoment
The early body systems and structures established in the embryonic stage continue to develop.
The neural tube develops into the brain and spinal cord, and neurons continue to form.
Once these neurons have formed, they begin to migrate to their correct locations.
Synapses, or the connections between neurons, also begin to develop.
Between the ninth and twelfth week of gestation (at the earliest), reflexes begin to emerge.
The fetus begins to make reflexive motions with its arms and legs.
Differentiation of Sex Organs
During the third month of gestation, the sex organs begin to differentiate.
By the end of the month, all parts of the body will be formed.
At this point, the fetus weighs around three ounces.
The end of the third month also marks the end of the first trimester of pregnancy.
So, what’s going on inside the brain during this important period of prenatal development?
The brain andcentral nervous systemalso become more responsive during the second trimester.
The lungs begin to expand and contract, preparing the muscles for breathing.
While development usually follows this normal pattern, there are times whenproblems with prenatal developmentoccur.
Takeaways
Brain development does not end at birth.
A considerable amount of brain development takes place postnatally, including growing insize and volumewhile changing in structure.
The brain quadruples in size between birth and preschool.
Frequently Asked Questions
The first 13 weeks of pregnancy are considered the most critical in prenatal development.
It is during this period that the embryo forms organs.
It is also the period when most miscarriages occur.
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