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Your baby’s brain is developing rapidly
Pregnancy

Your baby’s brain is developing rapidly

2 min readWeek 30
Key takeaways
2 min
  • Monitor your baby's rapid brain development as nerve cells form and brain surface area expands through new convolutions between weeks 28-33.
  • Expect increased fetal activity including stretching, kicking, and grasping movements as your baby grows more active during this trimester.
  • Include boron-rich foods like nuts in your diet to support healthy brain development and neural growth.
  • Prepare for gender-specific developments like testicular descent in boys and ovarian development in girls during weeks 28-33.
  • Schedule regular ultrasounds to monitor facial feature development and overall fetal growth progression.

A baby's brain develops rapidly during weeks 28-33 of pregnancy, with nerve cells forming and brain surface area expanding through new convolutions. The brain increases by one-third in size during this critical period before birth.

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Your baby’s brain is developing rapidly

Your baby is growing quickly and their internal organs are continuing to develop. They are also looking plumper, as subcutaneous fat continues to accumulate.

Your baby’s brain is developing rapidly - Your baby’s brain is developing rapidlyThe baby's skin is covered with a lubricant that protects it, as well as a light lanugo fluff that helps keep them warm. Gradually, these layers will begin to disappear [1].

The baby is now more active, they can stretch, kick and make grasping movements [2]. The brain is developing rapidly, nerve cells have formed, and the brain’s surface area is growing thanks to new convolutions (which are surface area folds), and boron, an element found in foods such as nuts [3]. Between this stage of pregnancy and the time of birth, the brain will increase in size by a third.

Between 28 and 33 weeks of age, boys’ testes will descend [4]. In girls, the ovaries and vagina have developed, and it is visible because the lower labia are still small and do not cover. This will happen closer to childbirth [5].

If you are expecting twins

If your babies have a common fetal sac, then your doctors will probably want to monitor you very closely because there is a greater risk of entanglement of the umbilical cords. You may even be admitted to the hospital early so they can readily perform ultrasounds and monitor the babies’ heartbeats.

What can be seen on ultrasound

The picture shows a close-up of the baby's face. They are lying on their right side. Facial features, including eyes and eyelashes, are visible, and their eyes are closed. The baby’s hand is also visible and extended forward.

Your baby’s brain is developing rapidly - Your baby’s brain is developing rapidly
Frequently asked questions

A baby's brain develops most rapidly during the third trimester, particularly between weeks 28-33. During this period, the brain will increase in size by about one-third before birth.

Boron, found in nuts and other foods, supports brain development by helping create new convolutions that increase brain surface area. A balanced diet with essential nutrients is crucial for optimal neural development.

Babies become more active during this stage and can stretch, kick, and make grasping movements. These movements indicate healthy muscle and nervous system development.

While there's no medical requirement, many parents choose baby names during the second or third trimester. Having names ready helps with hospital paperwork and bonding with your baby.

Ultrasounds can clearly show facial features including eyes, eyelashes, and hands. The baby's face becomes more defined and you may see them with eyes closed in their typical resting position.

Medical Disclaimer

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or qualified health provider with any questions you may have regarding a medical condition.

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Medically reviewed content

Reviewed by healthcare professionals · Updated June 5, 2025

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