Your Baby’s Progress
Great changes take place in the nervous system this month. The brain grows larger (to fit inside the skull, it has to fold over and wrinkle up until it looks like a walnut), and the brain cells and nerve circuits are all fully linked and active. In addition, a protective fatty sheath begins to form around the nerve fibers, just as a similar sheath formed earlier around the spinal cord, and this fatty myelin will continue to develop until early adulthood. As a result, nerve impulses can travel faster and your baby becomes capable of increasingly complex learning and movement. Your baby starts preparing himself for birth. (If he were to be born at this stage, he would have an excellent chance of survival.
Even though such a baby may have some breathing problems and difficulty in keeping himself warm, modern special-care facilities should help him thrive.) Some fat is beginning to appear underneath his skin, which smoothes out, loses its wrinkles, and becomes more rounded. His coat of hairy lanugo may diminish to a patch on his back and shoulders. The membranes that sealed and protected his eyes during their growth will, by the beginning of this month, have fulfilled their function, as his eyes are now fully formed and allowed his eyes to open. He will also continue to develop his swallowing and sucking skills.
He has now fully developed his mature breathing rhythm, and the air sacs in his lungs start to prepare for the first breath he will take in the world outside the uterus. They line themselves with a coating of special cells and a fluid (surfactant) the will prevent them from collapsing.
Over the course of this month, he will find he has less room to move around and will gradually give up moving so much. He will wriggle uncomfortably if you are in a position that doesn’t suit him.
During his weeks of “gymnastics practice,” he has done more than increase his muscle tone- he has developed the ability to orient himself in space. He will probably continue to lie in your uterus with his head upward during this month. However, if he is maturing very fast, he may turn upside down and settle into place for delivery, or engage, somewhat earlier than usual.
This is more common in first-born babies.