Fetal Development Weeks 31 Through 35
Will it be baby blues or a brown-eye girl? Your baby's iris color begins to appear around the thirty-first week. Most babies are born with dark blueish-brown or bluish-gray eyes, but this shade almost always changes after birth. True eye color won't be apparent for six to nine months -- final formation of eye pigmentation happens in response to exposure to the strong light of the outside world.
In the meantime, the fetus's eyes are being readied for life after birth. Pupils begin to dilate in response to the soft, pinkish-red light that filters into the uterus. Eyes are usually open during alert times and closed during sleep.
Take a deep breath -- that's what your baby is doing now, at least some of the time. Fetal breathing movements in the last third of pregnancy are intermittent -- after all, baby is getting her oxygen from the placenta, so breathing isn't really necessary. Plus, her lungs are taking in amniotic fluid, not air. But these "breathing lessons" help the lungs to grow strong. Recent studies have shown that this gentle work-out for the lungs also encourage its cells to produce more surfactant, the protein that is essential for the lungs' healthy development.
Strange but true: In human fetuses, breathing movements spike in the hours of darkness. Why? Scientists don't yet know.
Your baby doesn't have much elbow room these days -- and, happily, that's probably going to mean fewer elbow jabs to the ribs for you. Because space in the uterus is running out, the baby becomes less active at this point in the pregnancy. You may also notice that her movements are affected by your daily routine -- how much and when you eat, what position you are in, and sounds from the world outside can all affect your baby's activity level.
While fetal movements slow down, they're still going on. Take a little time each day to relax out and check the action. Your doctor will be able to give you guidelines on how much movement you should feel- for example, more than ten movements in two hours.
As of this week, your baby is no longer adrift in his private pond of amniotic fluid. He's gotten so big that he's no longer floating -- he's resting on your uterus instead. At this point, your baby is probably already in the position he'll be in at birth -- usually in what's called the "vertex" position, with head down, rear end up. Three to four percent of all babies will be facing the other way, with their bottoms or legs toward the cervix, in the "breech presentation."
Since a fetus rarely rotates on its own this late in the game, a doctor or midwife will sometimes try to coax it out of the breech position with a procedure called "external version." It involves manipulating the lower abdomen manually, and should be done in a hospital for proper monitoring of mom and baby.
Imagine you are holding a five-pound bag of sugar. That's what holding your baby might feel like right about now. In week 35, the average baby weighs in at around five to six pounds and measures about 16 to 19 inches in length. Still not considered "full term" (that'll happen at the end of the thirty-seventh week), her breathing and digestive systems are almost ready to roll, and she's beginning to develop her own immune system.
The tiny details of the fetus are complete at this point, too. Toenails are fully formed and fingernails reach over the ends of miniscule fingertips. Can a fetus feel an itch? We don't know that, but we do know that they often scratch themselves before birth.
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