Over the next two weeks he will mature enough that his chances of survival if born early will be pretty good. About 30% of triplets and 10% of twins are born at this time, however most often it is best for babies to stay in the uterus as long as possible.
In addition to looking like a newborn, your baby is beginning to react like a newborn. All five of her senses are now functioning. Your baby can see differences of light and dark through your skin, can hear what happens around you and within you, tastes the amniotic fluid, and feels the closeness of your uterine wall. This is also a peak week of movement for your baby. Soon, her size will restrict her to shifting instead of all-out kicks.
Another exciting change in your baby’s brain is he now experiences REM (Rapid Eye Movement) sleep. This is the deep stage of sleep where dreaming occurs. He sleeps a lot too. You have probably begun to be familiar with his daily patterns of awake and sleep just by paying attention to his movements.
Her body is very mature, and her lungs are well-developed which gives her good chances of survival if she were born this week. The vernix (white substance protecting her skin) is thicker, while the lanugo hair is almost completely gone. Her finger nails have grown to the end of her fingers, and she urinates almost a pint of fluid a day.
There is a wide variation in the size of babies by this time. The average is around 5.5 pounds (2550 g) and about 20.25 inches (45 cm) long. You are entering the time of most rapid weight gain, where your baby will be gaining ½ to ¾ of a pound each week. Fat is being deposited all over her body, and the final touches are being made to all the organ systems.
You should be feeling Braxton Hicks contractions pretty regularly now. They are not a cause of concern, simply your uterus muscle exercising itself to get stronger.
Your baby may have dropped down into the pelvis, called lightening or engagement, in preparation for birth. This causes your pelvis to expand which may cause some pelvic pressure. The ever increasing size of your baby may also be pushing him up into your rib cage, which may be feeling sore.
Your estrogen levels are increasing, making your uterus more sensitive to oxytocin (the hormone your body uses to cause contractions). This also changes the ratio of estrogen to progesterone which stimulates the release of prostaglandins (which your body uses to soften the cervix).
You may begin thinking about the upcoming labor. If you have not already signed up for a childbirth class or contacted a doula, you need to now.