Check out what happened with your baby's development last week.

Brow know-how. As if concentrating on a tricky math problem, your clever baby can furrow his brow. And now he's actually getting eyebrows to do it with! These fine hairs, like the hair on his scalp, don't contain any pigment yet—they're pure white. His eyelids are completely developed too, though they're fused shut until about 28 weeks.

Womb workout. "Waving my arms and legs is fun!" Jumping jacks may be your baby's favorite activity these days. Now that his arms and legs have reached their final proportions (but not their final size), he's exercising them vigorously—kicking, flexing, and clasping his hands. Speaking of his hands, fingernails now completely cover his fingertips, just as yours do. And they keep growing. In fact, you may need to trim your baby's nails right after he's born so he doesn't scratch himself.

Prepare for padding. Even though your baby measures more than 9.5 inches now, he still doesn't weigh much—about 13 ounces. At this point, he has only 1 percent body fat. But from here on out, he'll be adding layers of fat, which will help him to produce and retain body heat. Your little one's fat is a lot like the kind you're putting on during pregnancy. It's called brown fat and is readily turned into energy to keep both of you on an even keel.

Welcome respite. Despite the occasional aches and pains, this stage of pregnancy is fun! Your belly has grown enough for you to really "feel" pregnant, and the rest of the world knows it too. But you're not so big yet that you have trouble getting out of a chair or tying your shoes. Your morning sickness has probably ended, and your appetite's back, perhaps with a vengeance. Enjoy this time.

Under the weather. You may be feeling great in general, but we all occasionally get sick. If you do come down with a cold or the flu, the first thing you should do is let your health care provider know. Don't take any over-the-counter medications unless your doctor or midwife gives you the go-ahead. To encourage a speedy recovery, be sure to drink extra fluids, and try to eat regularly. We've all heard (from doctors and grandmothers alike) about the restorative powers of chicken soup. It's hot, liquid, and nutritious—everything you need when you're sick. It won't harm your baby if you don't eat well for a few days, but you'll recover more quickly if you can get some nourishment.

From the experts. You might be feeling some pelvic pain as your pregnancy progresses. "Pelvic pain that involves the pubic symphysis—the joint in the center of your pubic bone—is not uncommon during pregnancy," explains Elaine Zwelling, R.N., Ph.D. "Pregnancy hormones loosen your joints so your pelvic bones can spread during childbirth. This increases your flexibility, but it can also cause some pain." Learn about easing the discomfort from Dr. Zwelling.