Your developing baby – week 31

by Kaiser Permanente |
Fetus at week 31, illustration

Your baby weighs a little more than 3 pounds, is about 16 inches long, and is around the size of a coconut.

This week, you might notice that your baby has longer quiet times when sleeping. Most babies have regular patterns of waking and sleeping by week 31. 

It’s not too early to read to your baby. How about a favorite from when you were a child? 

In addition, your baby’s:

  • Nerve cells are connecting.
  • Five senses (touch, taste, smell, sight, and hearing) are working. However, your baby cannot smell anything yet because they're covered in amniotic fluid. These five senses are the foundation for bonding and attachment between you and your baby which begin during pregnancy, continue infancy and throughout life.
  • Brain grows and develops quickly and can now help control your baby’s body temperature.

Each day, your baby swallows amniotic fluid and also passes a few cups of urine into the amniotic fluid. The amniotic fluid now completely replaces itself several times each day.

Your baby has finished most of their major development. Weight gain will be the major change now.

This article has been created by a national group of Kaiser Permanente ob-gyns, certified nurse-midwives, pediatricians, lactation consultants and other specialists who came together to provide you with the best pregnancy, birth, postpartum, and newborn information.

Some of the content is used and adapted with permission of The Permanente Medical Group.