14 weeks

This week's big developments: Your baby can now squint, frown, grimace, pee, and possibly suck his thumb! Thanks to brain impulses, his facial muscles are getting a workout as his tiny features form one expression after another. His kidneys are producing urine, which he releases into the amniotic fluid around him — a process he'll keep up until birth. He can grasp, too, and if you're having an ultrasound now, you may even catch him sucking his thumb.

In other news: Your baby's stretching out. From head to bottom, he measures 3 1/2 inches — about the size of a lemon — and he weighs 1 1/2 ounces. His body's growing faster than his head, which now sits upon a more distinct neck. By the end of this week, his arms will have grown to a length that's in proportion to the rest of his body. (His legs still have some lengthening to do.) He's starting to develop an ultra-fine, downy covering of hair, called lanugo, all over his body. Your baby's liver starts making bile this week — a sign that it's doing its job right — and his spleen starts helping in the production of red blood cells. Though you can't feel his tiny punches and kicks yet, your little pugilist's hands and feet (which now measure about 1/2 inch long) are more flexible and active.