Baby Bolin: 15 weeks

At around 4 inches long, crown to rump, your baby now weighs about 2 1/2 ounces. He's busy inhaling and exhaling amniotic fluid, which will help develop the air sacs in his lungs. His legs are growing longer than his arms now, and he can move all his joints and limbs. That means his hands are more functional, too. Sweat glands are appearing.

Although his eyelids are fused shut, he can sense light. If you shine a flashlight at your tummy, he's likely to move away from the beam.

There's not much for your baby to taste at this point, but his taste buds are beginning to form.

And if you have an ultrasound, you may be able to find out whether your baby's a boy or girl! (Don't be disappointed if it remains a mystery, though. Nailing down the gender depends somewhat on how clear the picture is and the position of your baby during the ultrasound; he may be curled or turned in such a way as to keep you in suspense.)