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Pregnancy Week 39

Fetal Development at week 39

Contrary to popular understanding, human gestation actually requires nine and a half lunar months, not nine. These last two weeks are part of that additional period.

Your Baby

From about this point on, your baby will gain about 1⁄2 ounce (14 g) of fat each day it stays in your uterus. Over the next few days your baby’s lungs will begin to increase their production of a surfactant, which will keep the air sacs in the lungs open. The lanugo (downy hair that once covered your baby’s body) is disappearing. If any of the lanugo remains by birth, it will be found on the baby’s shoulders, forehead, and neck.

Your newborn may have no functioning tear ducts for a couple of weeks. The first cries are almost always tearless ones.

The color of your baby’s skin is beginning to change from reddish or pinkish to white or bluish pink (even in babies with dark pigmentation). Changes in your baby’s skin color are due to the growing thickness of the fatty layer under the skin’s surface. Earlier in development, the skin was so transparent and the body contained so little subcutaneous fat that if you could have seen your baby, you would have seen its organs through its skin. Now, the growing layer of fat gives your baby’s skin an opaque quality and masks the color of the muscles and circulating blood cells.


There are many reasons why you might have more difficulty sleeping from now on. The baby may be much more active, you may be experiencing periodic contractions, and you’re probably anxious and anticipating the birth. All of this is very predictable and common. When the baby settles deep into your pelvis, you may feel clumsy and off-balance. That’s because your center of gravity has shifted as the baby changed its position. You may notice more of a change in your gait since your balance is being thrown off by your enlarged uterus and the shifting position of the baby.