Your Baby’s Development: The Third Trimester

You’re two-thirds of the way to meeting your little one! A lot of exciting things will happen during this trimester, so keep reading for an in-depth look, week by week. 

Week Twenty-Eight

Your baby can partially open their eyes, and their eyelashes have formed. Their central nervous system can direct rhythmic breathing movements, as well as control body temperature. 

At this point, your baby is nearly 10 inches from the crown of their head to their bottom! 

Week Twenty-Nine

At this point, your baby is fully capable of kicking, stretching, and making grasping movements with their little hands. 

Week Thirty

Your baby’s eyes can open all the way now! They also might have a good head of hair by this point. Red blood cells are forming in your baby’s bone marrow. Your baby might be more than 10 ½ inches long now. 

Week Thirty-One

Thirty-one weeks into your pregnancy, 29 weeks after conception, your baby has completed most of their major development. At this point, your baby is going to start gaining weight very quickly. 

Week Thirty-Two

Your baby’s toenails are visible, and the layer of soft, downy hair that’s been covering your baby’s skin for a few months will start to fall off this week. Your baby is also beginning to practice breathing!

Week Thirty-Three

Your baby’s pupils can now change size in response to varying amounts of light. Their bones continue to harden, although their skull will stay soft and flexible for a while longer. 

Week Thirty-Four

Your baby’s fingernails have now reached their fingertips. They’re continuing to gain weight, and might be more than 4 ½ pounds at this point. 

Week Thirty-Five

Thanks to this rapid weight gain, your baby’s skin is now smooth, and their limbs are taking on a chubby appearance. 

Week Thirty-Seven

Thirty-seven weeks into your pregnancy, or 35 weeks after conception, your baby now has a firm grasp! To prepare for birth, they might start descending or “dropping” into your pelvis. If your baby isn’t head down, your healthcare provider will tell you some ways you can deal with that. 

Week Thirty-Eight

At this point, the circumference of your baby’s head and their abdomen are about the same. Your baby’s toenails are fully grown, and they’ve lost all of their lanugo. Your baby is probably around 6 ½ pounds at this point. 

Week Thirty-Nine

Your baby’s chest is still becoming more prominent. For baby boys, their testes continue to descend into the scrotum. Fat is still being developed all over your baby’s body, to help keep them warm after birth. 

Week Forty

Your due date is here! If you haven’t delivered already, your baby is most likely 14 inches long and around 7 ½ pounds. Always remember, though, that healthy babies come in a variety of different sizes. 

If your due date comes and goes with no signs of labor, don’t worry! Your due date is simply an estimate of when your pregnancy will be 40 weeks long—not an estimate of when your baby will arrive. It’s completely normal to give birth before or after your due date. 
Read our blog about common signs of labor, here!