Expectant mothers are always excited and curious to know about the growth of their little one inside their womb. Besides the physical growth, metal growth is imperative. A specific timeline for the brain development of the fetus is necessary for the mother to act accordingly to ensure the healthy growth of the fetus.
How a brain works, and what makes it tick has always intrigued and mesmerized researchers. All progress and regression in our life can be easily attributed to the way our brain works, thinks, deduces, reasons, concludes, etc. Life starts at with the fertilization of the egg, until the eighth week it is called as an embryo. From the eighth week until the moment of birth, it is known as fetus. Brain development involves the formation of the brain, nervous system and spinal cord, it all begins at the embryonic stage itself.
Did You Know ?
Genes contributes to about 60% of brain development, environment in uterus to about 30% and maternal nutrition to about 10%! Although genes provide the basic blueprint for fetal brain development, its sound development depends upon certain external factors such as nutrition and well being of mother, avoidance of exposure to toxins etc.
Brain Development Timeline
Fetal Brain Development Week 1-2 (First Trimester)
The egg gets implanted into the uterine wall, and conception is considered as two weeks old.
Fetal Brain Development Week 3
The egg is now a ball of cells called as the blastocyst. The eggs has a unique DNA that carriers the necessary information. Of the two strands, one comes from the father and the other from the mother. There are two types of cells, the inner cells which will later form the embryo and the outer cells which will form the membrane.
Fetal Brain Development Week 4
The blastocyst can now be called an embryo as it has now reached the uterus and buried itself in the wall. The uterus wall has become thick enough to support the baby. The embryo will now receive all the nourishment from the mother. In this phase, the embryo further develops the three brain sections; forebrain, middle brain and hind brain, along with the optical stalk.
Fetal Brain Development Week 5
The first sign of the cerebral hemisphere is visible at this stage. As the brain continues to develop, other organs like the circulatory system begins to function with all four chambers of the heart present. We can see upper and lower limb buds. The heart too starts to beat with twice the rate of the mother.
Fetal Brain Development Week 6
This week sees the formation of the brain hemispheres and also some wave activity. The neural tube that connects the brain and spinal cord also closes in this duration. The formation of the Pituitary, Thymus and Parathyroid begins too.
Fetal Brain Development Week 7
By this week, the brain is growing at a rapid rate. The eyelids and ears have started to form and also the genital area.
Fetal Brain Development Week 8
In this week, the head is quite large, as compared to the rest of the body. The development of the hind brain, responsible for regulating heartbeat, breathing and all concerned muscle movements also begins now.
Fetal Brain Development Week 9
The nervous system, by now, is quite developed for proper functioning. The genital region for both the sexes look alike.
Fetal Brain Development Week 10
The genitals begin to develop at this stage, determining the sex of the fetus. Brain development is also very rapid as the brain is forming 250,000 neurons per minute. The eyelids and ears are developed and the embryo is now a Fetus.
Fetal Brain Development Week 11-14 (Second Trimester)
The spinal cord is clearly defined and the spinal nerves start to stretch out from the spinal cord.This week sees the completion of the first trimester. The sex of the baby can be determined in this period. The heart, liver, spleen and many other organs are already functioning. By this stage, the baby is taking plenty of nourishment through the placenta. The fetus also begins its practice of breathing, inhaling, and exhaling. The eyelids will close and not open until the 28th week.
Fetal Brain Development Week 15
The baby’s torso is now growing rapidly and it is completely covered with lanugo; fine hair that protects the skin. The sense of hearing also sharpens at this stage. The pituitary gland is well developed.
Fetal Brain Development Week 16
The baby makes its presence known by pulling and tugging on the umbilical cord. The cerebrum is in a further stage of development.
Fetal Brain Development Week 17
At this stage, the uterus begins to expand, to give more room to the baby. As the bones are growing and becoming hard, it needs protection. The spinal cord is protected by a barrier made of a substance called ‘myelin’.
Fetal Brain Development Week 18
The baby develops sensitivity to light and at the same time, the brain is growing rapidly. The Operculum starts developing at this stage.
Fetal Brain Development Week 19
The brain becomes capable of forming millions of motor neurons, enabling the baby to develop and make muscle movements voluntarily. The forebrain further develop into left and right cerebral hemispheres of the brain. The nerve cells required for the processing of all the senses are also developing rapidly. This is the stage where your baby can hear you.
Fetal Brain Development Week 20
Nerve cells at this stage make complex connections and sensory perception with the brain and the entire body. This development carries on until the age of 5 or 6.
Fetal Brain Development Week 21
Rapid growth and development of the fetus slows down in this week. The organs, especially the heart is getting stronger, and fat is getting accumulated in the baby’s muscles.
Fetal Brain Development Week 22
As the brain is understanding complex sensory perceptions, the fetus becomes capable of distinguishing between different sounds.
Fetal Brain Development Week 23
All the nerve cells that so far had formed and developed independently, begin to join to form a complete nervous system.This is the age where the fetus can respond to aversive stimuli.
Fetal Brain Development Week 24
At this stage, the brain starts to regulate all body functions, and activates the auditory and visual systems, which heightens the baby’s overall senses.
Fetal Brain Development Week 25
The spinal cord begins to harden and straighten out. Nervous system is more developed and capable of controlling voluntary breathing. The optic nerve is highly heightened in perceiving light from any direction. This stage marks the development of the lateral sulcus.
Fetal Brain Development Week 26
So far the brain was smooth in its form, but at this stage its tissues begin to develop creased, wave-like formations. The brain waves also get stronger at this stage enhancing auditory and visual sensors.
Fetal Brain Development Week 27
As the brain is actively processing many senses, it is quite possible that your unborn will begin to dream. Brain tissues are also developing fast.
Fetal Brain Development Week 28 – 40 (Third Trimester)
The brain completely monitors the breathing and regulates the body temperature. This being the beginning of the third trimester, the brain continues to grow and increase rapidly in size, all the while establishing connections between the nerve cells. The brain along with the lung is the last organ to develop, and the process is completed, close to the end of the third trimester. A newborn’s brain is only about one-quarter the size of an adult’s.
Brain Development Issues
The environmental, physical and emotional being of the mother, all have a profound effect on fetal brain development. The result of this is mental and cognitive disabilities. Throughout pregnancy, the fetus’s brain is vulnerable to disruptions that may cause death, or mental disabilities and other physical developmental delays.
Alcohol and Drugs
Alcohol, smoking and drug abuse have been linked to disabilities, impairments and ADHD. Fetal alcohol syndrome is a disorder that occurs when a pregnant woman ingests alcohol during pregnancy. Alcohol can stunt fetal growth, weight and overall development. Studies have shown that women who smoke have smaller babies that have mental as well as physical retardation. Drugs like marijuana contain the active ingredient tetrahydrocannabinol (THC), that suppresses normal growth of the nerve cells.
Did You Know ?
Alcohol, drug intake and smoking have been strongly condemned by the US Surgeon General, the UK Department of Health and almost all medical departments of the world.
Genetics and Hereditary
Genetics and hereditary, too, play a part in causing damage to a fetus’ brain. As the fetus grows, it can inherit a brain dysfunction or an impaired cell leading to mental disorders. Toxins in the environment like cadmium, lead, etc., can get absorbed in the soil, then into our water and food, or even in the air, exposing the fetus to neurological damage. Even exposure to radiation can cause fetal brain damage.
Mental, Physical or Sexual Abuse
Any kind of abuse – mental, physical and sexual – can cause harm to the fetus. Fear and mental trauma can fluctuate blood pressure. The fetus receives all its nourishment from the placenta, which gets disrupted as a result of high or low blood pressure. The placenta sends oxygen to the fetus, which is essential for brain development. Excess or reduced oxygen damages the brain. A woman falling on her belly or back, will increase the chances of the fetus’ soft skull getting damaged.
Did You Know ?
There are instances where the child has developed mental impairment during the childbirth process.
Brain development in a fetus and its associated problems are still being researched. Hence, there are no specific answers to the how’s and why’s of brain development. However, what does not change is the wonder of a cell, an embryo that develops into a fetus, then a child and finally, an adult going through the passage of time, and physical, mental and cognitive development.
Disclaimer: This article is for informative purposes only, and should not be used as a replacement for expert medical advice.