Your growing baby

The third trimester is a time of steady growth as your baby matures and gets ready for birth. As your baby gains weight, fat is stored under the skin. This smooths your baby's skin and makes your baby look plumper.

During the beginning of this trimester, you may feel plenty of kicks, squirms, flips, hiccups and other movements in between quiet periods. Your baby starts having regular sleep and wake cycles, and you will notice the difference in activity. You may also notice your baby responding to bright light as well as sound.

By the 28th week your baby has eyelashes,and his hair is growing. His fingernails have grown to the end of his fingertips. The lanugo, the downy hair, is beginning to disappear. This is also the start of dramatic brain growth that will continue for your baby's first two years.

Your baby's lungs are beginning to reach maturity, meaning your baby would have a good chance of surviving if born now. Your baby is about two pounds and is about 13 inches from crown to rump.

At 32 weeks your baby has grown so much that there is much less room to move around. You can feel the difference in your baby's movements, which are more like wriggling and twisting.

Your baby may settle into a favorite position. That can make it easier to identify his feet, elbows and hands when these push against the wall of your uterus. The vernix coating on your baby's skin is beginning to be absorbed.

Starting in week 36, your baby gains about half a pound and grows half an inch a week. Many babies turn head-down and stay in that position for birth.

First babies are likely to settle into the mother's pelvis at about week 38. This act of the head engaging in the pelvis is called lightening. It makes your breathing easier but creates pelvic pressure. If this is not your first baby, your baby's head may not engage until you go into labor.

After week 37, your baby is considered "term," which means fully-grown. Term babies often weigh 7 to 8 pounds and are 18 to 21 inches long, measuring from crown to rump.

Baby's development: Weeks 27 to 40

Week 27

Your baby's hair is longer. His or her eyelashes and eyebrows are very noticeable now.

Week 28

Your baby is also opening and closing his or her eyes and reacting to light. He or she Your baby is about 2 pounds and is about 13 inches from crown to rump.

Week 29

Your baby will gain about 7 ounces each week. He or she can kick, stretch and make grasping movements

Week 30

All of baby's senses are developed. Your baby starts having regular sleep and wake cycles, and you will notice the difference in activity.

Week 31

Vernix (a white coating on the skin) and lanugo (the fine hair that covers the baby's body) begin to disappear. Baby's head is more in proportion to the body.

Week 32

Your baby's skin is less wrinkled. He or she is about 18 inches long and weighs about 5 pounds.

Week 33

Most babies have moved to a “head down” or cephalic position in the uterus by this time, and most will stay in that position until delivery.

Week 34

Your baby's skin is becoming pinker and he or she is blinking.

Week 35

Your baby's fingernails and toenails have grown to the end of his or her fingers and toes.

Week 36

Most of your baby's organs are now mature and the lungs continue to mature. Your baby's skin is red but smooth. He or she is about 19 inches long and weighs about 6 pounds.

Week 37

As your baby gains weight, fat is stored under the skin. This smooths your baby’s skin and makes your baby look plumper.

Week 38

Your baby gains about 1 ounce each day. He or she may move down into your pelvic area.

Week 39

Your baby is fully developed. He or she is about 20 inches long and weighs 7 to 8 pounds. Fine hair remains only on arms and shoulders. Fingernails are now beyond the ends of fingertips.

Week 40

It's your due date! Your due date is only an estimate for when your baby is likely to be born. Most babies are born between 37 and 42 weeks.

Source: Allina Health's Patient Education Department, Beginnings: Pregnancy, Birth and Beyond, seventh edition, ob-ah-90026
First Published: 10/04/2002
Last Reviewed: 12/02/2015

Did you know?

Although many people consider pregnancy to last nine months, it is actually 280 days, measured from the first day of the last menstrual period, or 40 weeks.

The "due date" is day 280 or the end of the 40th week.