Your baby’s brain starts developing early in pregnancy, just three weeks after fertilization, and continues throughout your pregnancy. The third trimester is the time when major developments occur and your baby’s brain triples in weight. Taking folic acid and eating a balanced diet that includes omega-3-rich fish can help support during and after pregnancy.
It’s probably not surprising that your baby’s brain is one of the first major organs to begin to develop. But you may not know that your child will continue to grow until they are in their early 20s!
The brain and spinal cord together make up the central nervous system. The brain is contained within the skull, and the spinal cord is contained within a flexible spinal cord made up of 33 separate bones (vertebrae). A network of nerves leaves the spinal cord, and these nerves send signals to and receive information from various organs.
Early fetal brain development
The first portion develops as an oval-shaped disc of tissue called the neural plate, just three weeks after fertilization. This early (5 weeks pregnant), your baby is an embryo that looks like a small tadpole, and the nerve plate runs down the middle from head to tail.
During this week, the edges of the plate rise and fold towards each other, forming the neural tube that will become your baby’s spine and brain. At this point, the ends of the tube remain open and the brain begins to form at the top of the tube. Near the bottom is the structure that will eventually become the tailbone.
When you are 6 weeks pregnant, the two ends of the neural tube are completely closed, and at the top of the tube the brain consists of three areas:
- The forebrain turns into the cerebrum, which controls certain brain functions such as thinking and problem solving.
- The midbrain is involved in processing visual and auditory information.
- The hindbrain transforms into the medulla, which is the control center of the body’s automatic activities such as blood pressure and heart rate, as well as the cerebellum, which manages balance and coordination.
How does the baby’s nervous system develop?
It is the neural crest located along the edges of the developing neural tube. This apex forms the brain and spinal cord, along with millions of nerves that spread throughout the body.
From 8 weeks of pregnancy, these nerves connect not only with each other, but also with muscles and other tissues, as well as organs such as eyes and ears. At 12 weeks, the nerves begin to send simple signals that cause reflex behavior. For example, your baby’s fingers may open and close and his toes may curl. Your baby may also contract his eye muscles and make sucking motions with his mouth.
By about 28 weeks, nerves connect with their designated organs so your baby’s senses of hearing, smell and taste can start working. Some nerve cells develop a sheath of insulating material called myelin that speeds up signals between nerves. Myelin begins to form in the third trimester and continues after birth and into adulthood.
Although it happens throughout brain development, it really kicks into high gear during the last trimester as brain weight triples. During these last weeks, the brain also develops deep grooves in the skull that provide extra surface area without taking up more space. This wrinkled outer layer is known as the cerebral cortex.
How well does your baby’s brain work at birth?
Your newborn comes equipped with all sorts of fascinating abilities that reflect incredible growth, from the tiny neural plate to the full-fledged nervous system:
- They will have a wide variety of reflexes that you can test yourself. For example, if you stroke your baby’s cheek, he will turn his head towards you (rooting reflex). Put your finger in their mouth and they will automatically start sucking (sucking reflex). When you hold your baby upright with his feet touching the ground, he will make small stepping movements (stepping reflex).
- Your baby can recognize your voice! From the third trimester, your little one can listen to your conversations and when they are born, they will clearly prefer your voice over others. Your little one will even turn their head when they hear you.
- You might think your baby would be just as interested in looking at a toy or the TV, but research shows that babies are particularly adapted to human faces and prefer them to random designs.
And remember, because your baby’s brain continues to grow after birth, new neural connections are formed every day between different parts of the brain, adding to your child’s growing store of knowledge, memory, and experience. Find out how you can help raise a smart baby.
What you can do to support fetal brain development
- Take a supplement during (and even before) pregnancy. Folic acid is a B vitamin that is very important for the development of the brain and spinal cord. Getting enough folic acid reduces the risk of neural tube defects such as spina bifida and anencephaly. The neural tube develops very early (many women don’t even know they’re pregnant), so experts recommend taking 400 micrograms of folic acid a day for at least a month before trying to get pregnant. You can take it from some prenatal vitamins or take it as a separate supplement.
- Eat cooked fish 2 to 3 times a week. Fish—especially oily fish like salmon—contains fatty acids, which studies show support your baby’s brain development during pregnancy and childhood. Check out our topic.
Fetal brain development week by week
|pregnancy week||Turning point|
|5 weeks||Neural plaque is formed.|
|6 weeks||The neural tube forms and closes. The brain now consists of three regions (forebrain, midbrain, and hindbrain) and ventricles have formed.|
|8 weeks||A neural network begins to spread throughout the body.|
|12 weeks||Fetal reflexes are present.|
|28 weeks||The senses of hearing, smell and touch are developed and functional.|
|28 to 39 weeks||Brain weight triples and deep grooves develop in the brain to provide more surface area for brain neurons. Myelin begins to develop along certain nerve pathways.|