Week 14

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.

Week 13

Fingerprints have formed on your baby's tiny fingertips, her veins and organs are clearly visible through her still-thin skin, and her body is starting to catch up with her head — which makes up just a third of her body size now. If you're having a girl, she now has more than 2 million eggs in her ovaries. Your baby is almost 3 inches long (the size of a medium shrimp) and weighs nearly an ounce.

Week 12

The most dramatic development this week: reflexes. Your baby's fingers will soon begin to open and close, his toes will curl, his eye muscles will clench, and his mouth will make sucking movements. In fact, if you prod your abdomen, your baby will squirm in response, although you won't be able to feel it. His intestines, which have grown so fast that they protrude into the umbilical cord, will start to move into his abdominal cavity about now, and his kidneys will begin excreting urine into his bladder.

Meanwhile, nerve cells are multiplying rapidly, and in your baby's brain, synapses are forming furiously. His face looks unquestionably human: His eyes have moved from the sides to the front of his head, and his ears are right where they should be. From crown to rump, your baby-to-be is just over 2 inches long (about the size of a lime) and weighs half an ounce.

Week 11

Your baby, just over 1 1/2 inches long and about the size of a fig, is now almost fully formed. Her hands will soon open and close into fists, tiny tooth buds are beginning to appear under her gums, and some of her bones are beginning to harden. She's already busy kicking and stretching, and her tiny movements are so effortless they look like water ballet. These movements will become more frequent as her body grows and becomes more developed and functional. You won't feel your baby's acrobatics for another month or two -- nor will you notice the hiccupping that may be happening now that her diaphragm is forming.