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Your baby’s development during your third trimester of pregnancy

Birthing Positions - Parents Canada


From the first signs and symptoms of pregnancy, your body has been undergoing important changes. At the same time, your baby has been developing at a rapid rate, with landmark achievements week after week. Learn about all of the important milestones at each stage during your third trimester of your pregnancy, including some advice on how you can contribute to your baby’s development.

Third Trimester Development by Gestational Age

Gestational AgeDevelopment

27-30 weeks
  • He is gaining his
    sense of smell
  • He may react to
    sounds, such as songs that you sing to him.
  • He will begin to
    put on baby fat.
  • He will weigh between 1-1/2 pounds and 5 pounds, and will measure 12-18
    inches in length.
31-35 weeks
  • His activity may decrease as he has less
    space in which to move.
  • He will develop a sleep pattern, which may or
    may not match yours.
  • He will receive antibodies from you to
    protect him from illness.
  • His brain is establishing billions of complex
  • He will weigh 4-5 pounds at week 32, and will gain up to 1/2 pound per
    week this month.

35 weeks
  • At 37 weeks, he is considered full-term.
  • His body and brain may be ready for life
    outside the womb.
  • He will move into fetal position and drop
    down into your pelvis.
  • He may be around 7 pounds, and between 18 and 21 inches long.

Did you know?

A baby’s brain growth advances dramatically during the 3rd trimester. In fact, the size of a baby’s brain increases approximately 10 times from the beginning of the 3rd trimester through the 1st year of life.

A baby’s brain contains Omega-3 fat and most of that fat is DHA, a key building block of the brain. That’s why it’s important to get DHA while you’re pregnant, especially during the last 3 months.

Learn more at: Whydha.com.

Seventh Month of Pregnancy (27-30 weeks)

Brain and Personality Development

Between weeks 27 to 30, your baby’s brain will take on the “folded” shape of a mature brain. He is producing the billions of neurons and synapses needed to make complex connections and may begin to form memories.  He may also begin to exhibit future personality traits via his behaviour in the womb, i.e. if he is very active or mostly calm. As his hearing and memory develop, you will feel him reacting to sounds like the songs you sing to him.

Sensory Development

Your baby’s olfactory neurons, or nerve cells that relate to smell, developed early on, however it is at this point that they can now detect odours. Smell is yet another way your baby can recognize and make sense of the world around him. During the third trimester, his sense of smell will greatly improve. Soon, he’ll be able to react to strong odours by grimacing or moving his head. And after birth, he’ll be comforted by the familiar smell of Mom. His sense of taste also becomes more refined at this time. Many of your baby’s taste preferences will be influenced by the flavours he is experiencing in your prenatal diet. If you choose to breastfeed, your baby will recognize and be comforted by those flavours in your breast milk.

Body Fat

Your baby is beginning to develop body fat layers that will regulate his body temperature and provide energy stores after birth.

Eighth Month of Pregnancy (31-35 weeks)

Brain Development

Your baby’s brain is advancing rapidly by producing tiny neurons and synapses, which will interconnect to provide him with the skills such as sucking, swallowing and breathing, enabling him to feed as soon as he is born.

Antibodies and Immunity

During the last weeks of pregnancy, you pass along antibodies to your baby in your blood. These will help protect him from many illnesses and infections he may face in the months after birth. This immunity lasts for a few months until he develops his own resistance. Breastfeeding can prolong the immunity by providing your baby with even more antibodies.

Preparation for Delivery

At this point, your baby will gain up to 1/2 pound a week. He is stocking up on calcium, fat, phosphorus and other essential nutrients he will need when he’s born. As your baby gets larger and stronger, his movements may feel more pronounced.

Ninth Month of Pregnancy (35 weeks – delivery)

Brain Development

During weeks 36 to 40, your baby continues to make the necessary connections that he will need to support his cognitive development (learning). His brain is now ready for life outside the womb. In order for your baby to reach all of these milestones, he must receive the proper nourishment. Contribute to his success by consuming a well-balanced diet of, wholesome foods that provide valuable nutrients such as DHA, a type Omega-3 fat and an important building block of a baby’s rapidly developing brain.

Week by Week Development through Pregnancy

Watch this episode of Amazing Milestones, designed to provide you with expert advice and pertinent information for everything “baby”.

This episode will discuss what to expect during pregnancy. With the help of our guest, Dr. Benoit, we will go step-by-step through each trimester to discuss what you might be experiencing, how to cope and what to expect in the months to come.

 Brought to you by Enfamil Canada.
Sign up for Enfamil Family Beginnings and get over $160 in coupons, samples and special offers!

a man carrying two children

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