From Giggle Glow:
Your baby is growing quickly now, and will be gaining around half a pound a week for the next couple of months. Remember that downy soft hair called "lanugo" we mentioned a while back? It's starting to disappear now because your baby is getting better at regulating body temperature. Your baby's brain is seeing some big changes in appearance, too. The surface is starting to develop those grooves and indentations that allow for more brain tissue to develop.
From The Bump:
Baby's now the size of a squash!
As baby's skin smoothes out, her brain just keeps getting more wrinkled. All those grooves and indentations increase surface area, meaning more room for that oh-so-essential brain tissue. She's also adding some brawn -- her grip is now strong enough to grasp a finger.
From What to Expect:
Your baby's height and weight haven't changed much in the past week, but the big news is your baby's brain gain. Until now, the surface of your baby's brain was smooth. Now, your fetus's brain is taking on those characteristic grooves and indentations. The reason for this change in appearance? Those wrinkles allow for an increased amount of brain tissue — a necessary change as your developing baby prepares for life outside your womb, and the street smarts he or she will need.
Another big change at 30 weeks pregnant: Your baby's bone marrow has taken over production of red blood cells (before, tissue groups and then the spleen took care of producing the blood cells). This is an important step for your baby, because it means he or she is better able to thrive on his or her own once born (with a little TLC from you, of course).
So it's in with the new (brain cells, red blood cells) and out with the old (lanugo). Much of the lanugo — the soft, downy hair covering your baby's body — is beginning to disappear now because both fat and the brain are regulating your baby's body temperature (so no need for that furry coat anymore). But you may see a few leftover strands of fur on your newborn's back and shoulders.