Baby Growth During the 3rd Trimester: Week-by-Week Guide

Finally, you’ve reached the final phase of pregnancy. The wait is going to end soon.

But curiosity is still there, and you get eager to know what goes inside the womb and how your little one develops during these last few months. Buckle up as we will unveil the baby’s growth during the third trimester.

These are the critical phases in which your baby will experience some of the largest developments that prepare them to live outside the womb. Your little one is getting ready for weight gain to vital organs and reflexes for the big debut into the great world.

So, without further ado, let’s find out what happened during the 3rd trimester of pregnancy.

Baby Growth During the 3rd Trimester: From Week 28 to Week 40

The first two phases, i.e., the 1st and 2nd trimesters of pregnancy, lay the foundation for your baby’s development, with the 1st trimester focusing on the early formation of organs and systems and the 2nd trimester marked by rapid growth and the development of sensory abilities. However, the third trimester is exciting as your little one getting ready to make their grand entrance into the world. Let’s take a look at what’s happening week by week.

Week 28: Your baby’s eyes can partially open 

Can you believe it? Your little one’s beautiful eyes are starting to open up, giving them a glimpse of the world they’ll soon be a part of. Their eyelashes have also formed, adding to their adorable features. At this stage, their central nervous system is capable of directing rhythmic breathing movements and regulating body temperature. How amazing is that?

Key highlights:

• Baby’s eyes partially open
• Eyelashes have formed
• Can regulate breathing and body temperature

Week 29: Time to kick and stretch 

Your little acrobat can now kick, stretch, and make grasping movements. It’s like they’re practicing their moves for their big debut! You might even feel some of those wiggles and kicks from the inside.

Key highlights:

• Baby can kick, stretch, and grasp
• Getting ready for their grand entrance

Week 30: A head full of hair 

As we approach the 30-week mark, your baby’s eyes can now open wide, and they might even have a full head of hair! Isn’t that just the cutest thing? And here’s another exciting development – their bone marrow is starting to produce red blood cells.

Key highlights:

• Eyes can open wide
• Baby might have a head of hair
• Red blood cell production begins

Week 31: Rapid weight gain time 

Your little one has completed most of its major development milestones, and now it’s time to pack some pounds! From this point on, your baby will rapidly gain weight and get ready to be a healthy, chunky bundle of joy.

Key highlights:

• Major development milestones are complete
• Rapid weight gain phase begins

Week 32: Breathing practice 

Your baby’s toenails are now visible, and the soft, downy hair (lanugo) that has been covering their skin starts to fall off. But the real highlight of this week is that your little one is practicing their breathing skills!

Key highlights:

• Toenails are visible
• Lanugo starts to fall off
• Baby practices breathing

Week 33: Light detection 

Your baby’s pupils can now change size in response to light! Their bones are also hardening, although their skull remains soft and flexible for now. It’s like they’re getting ready to take in the world around them.

Key highlights:

• Pupils react to light
• Bones are hardening
• Skull remains soft and flexible

Week 34: Fingernails reach the tips 

As your baby grows, their fingernails have now reached their fingertips. It’s like they’re getting their little hands ready to explore and grab onto everything in sight!

Key highlights:

• Fingernails reach the fingertips
• Baby is growing rapidly

Week 35: Smooth skin and chubby limbs 

Your little one’s skin is becoming smooth, and their limbs are taking on a deliciously chubby appearance. It’s like they’re getting all ready to be cuddled and snuggled by their adoring parents!

Key highlights:

• Smooth skin
• Chubby limbs
• Getting ready for cuddles

Week 36: Running out of room 

As your baby takes up most of the amniotic sac, the crowded conditions might make it harder for them to give you those powerful kicks and punches. But don’t worry, you’ll still feel plenty of stretches, rolls, and wiggles as they try to get comfortable in their cozy little home.

Key highlights:

• Baby takes up most of the amniotic sac
• Less room for kicks and punches
• Still lots of wiggles and rolls

Week 37: Head down position

Your baby’s firm little grasp is getting stronger, and it might start descending into your pelvis, getting into the head-down position for birth. If they’re not in this position yet, don’t worry – your healthcare provider will discuss ways to encourage them to get into the optimal position.

Key highlights:

• Baby has a firm grasp
• Might start descending into the pelvis
• Healthcare provider will advise on positioning

Week 38: Toenails and shedding lanugo 

Little by little, your baby is getting all dolled up for their big debut! Those tiny toenails that were barely visible a few weeks ago have now grown to the tips of those adorable little toes. And that fuzzy coating of lanugo – that soft, downy hair keeping your babe all cozy in the womb – well, most of it has been shed off, giving you a sneak peek at their velvety newborn skin. 

Key highlights:

• Toenails reach the tips
• Most lanugo has been shed
• Baby is growing bigger and bigger

Week 39: Prominent chest and descending testes 

Your baby’s chest is becoming more prominent, and for any little boys out there, their testes continue to descend into the scrotum. Your little one is also getting extra padding all over their body to keep them nice and warm after birth.

Key highlights:

• Prominent chest
• Testes descend for baby boys
• Added fat for warmth after birth

Week 40: Your due date arrives! 

Congratulations, mama! You’ve made it to the 40-week mark, which means your little one might be around 14 inches long and weigh around 7 1/2 pounds. Of course, every baby is different; some might arrive a little earlier or later than their due date. Remember, your due date is simply an estimate, and your baby will appear when they’re good and ready!

Key highlights:

• Baby might be around 14 inches and 7 1/2 pounds
• Every baby is different in size
• Due date is just an estimate

There you have it, mamas – a week-by-week glimpse into the final stretch of your incredible journey. Enjoy these last few weeks of pregnancy and get ready to meet your little one face-to-face! If you want to what things you should keep in mind during the 3rd trimester, then read our this blog.

Final Thoughts 

Alright, we’ve covered all the important details about your baby’s growth during the third and final trimester. This home stretch can feel like a marathon, but you’ve got this! Just keep taking great care of yourself like you did earlier on.

One simple but powerful thing you can do is read books out loud. Your little one is listening and getting familiar with your voice. Pretty cool, right? Reading helps nurture that budding bond.

I know the idea of delivery can be daunting, but try to stay positive. Millions of mamas before you have been through it. You are strong and capable of facing this challenge head-on when the time comes.

If any other questions or worries pop up, don’t hesitate to drop them in the comments below. This community is here to support you every step of the way. You’ve got this, mama!

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