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The Third Trimester: Your Baby’s Growth and Development

Third-Trimester A close up image of a growing baby bump!
Your baby (and bump) will grow rapidly in the third trimester!

Welcome to the home stretch, Mama! The third trimester!

You are SO CLOSE to meeting your precious little one.

While you’re working hard to nourish your baby and continue to provide the ideal environment in which they can thrive, this can start to take more of a physical toll on you in the third trimester. While the second trimester likely brought relief from a lot of the bothersome symptoms of the first trimester (such as nausea and fatigue), some of these things do return in the third trimester.

For some women, this can mean nausea creeps back in, or the start to experience headaches as well as other aches and pains. Heartburn is also common, as is fatigue, insomnia and stretch marks. This is also the time when Braxton Hicks might start to make an appearance – these are false contractions that shouldn’t be painful, but may stop you in your tracks!

While there’s certainly a lot going on that you can see externally – there’s also some incredibly exciting things happening in-utero! Let’s explore your baby’s third trimester development together.

Your baby’s growth in the third trimester:

  • Your baby can see and hear and their brain continues to mature.
  • The kidneys and lungs continue to mature in anticipation of life on the outside.
  • Your baby cries in-utero and may suck its thumb.
  • Your baby’s skill bones remain soft so that when it comes time to be born, it is easier for them to move through the birth canal.
  • In the final few weeks, your baby’s head will likely engage into your pelvis. This is called “lightening” and it may cause you to feel increased pressure.
  • Baby’s skin is still covered in vernix caseosa – a thick, white and cheesy substance that protects their skin. For many babies, this will still be present at birth.
  • By the last couple of weeks, the fine hair that covered baby’s skin since the second trimester (lanugo) has mostly disappeared.
  • Baby’s movements are becoming more intense – this is such a special and exciting time to start bonding with your little one.
  • Your little one is growing rapidly and increasing their fat stores – this trimester is when they gain the most weight! They are storing
  • By week 38-40 your baby’s lungs are usually fully matured and ready to breathe earth-side!
  • Remember your due date is just an estimation – only 5% of babies are born on this exact date! Most births occur between 39-41 weeks.

Pregnant Mamas make sure you check out our FREE Prenatal class that 8 out of 10 new mothers say they wish they took before birth to ease their stress and worries. You can even watch it at your own pace from the comforts of your own home! Sign up here

It’s important to note that pregnancy should be discussed with a healthcare provider to ensure safety and suitability for individual circumstances. This blog is general education only. For any personal based advice regarding you or your baby please seek advice from your own healthcare professional.

  1. Department of Health & Human Services. (02-2012). Pregnancy - week by week. Better Health Channel.
  2. Fetal development: The 3rd trimester. (2022, June 3). Mayo Clinic.
  3. How your fetus grows during pregnancy. (December, 2021). ACOG.
  4. Professional, C. C. M. (March 3, 2023). Fetal development. Cleveland Clinic.
  5. Stages of pregnancy | Office on Women’s Health. (February 22, 2021).
  6. Third trimester. (2022). Raising Children Network.