Get ready for a growth spurt. In the next few weeks, your baby will double his weight and add inches to his length. Right now, he's about the size of an avocado: 4 1/2 inches long (head to rump) and 3 1/2 ounces. His legs are much more developed, his head is more erect than it has been, and his eyes have moved closer to the front of his head. His ears are close to their final position, too. The patterning of his scalp has begun, though his locks aren't recognizable yet. He's even started growing toenails. And there's a lot happening inside as well. For example, his heart is now pumping about 25 quarts of blood each day, and this amount will continue to increase as your baby continues to develop.
Your growing baby now measures about 4 inches long, crown to rump, and weighs in at about 2 1/2 ounces (about the size of an apple). She's busy moving amniotic fluid through her nose and upper respiratory tract, which helps the primitive air sacs in her lungs begin to develop. Her legs are growing longer than her arms now, and she can move all of her joints and limbs. Although her eyelids are still fused shut, she can sense light. If you shine a flashlight at your tummy, for instance, she's likely to move away from the beam. There's not much for your baby to taste at this point, but she is forming taste buds. Finally, if you have an ultrasound this week, you may be able to find out whether your baby's a boy or a girl! (Don't be too disappointed if it remains a mystery, though. Nailing down your baby's sex depends on the clarity of the picture and on your baby's position. He or she may be modestly curled up or turned in such a way as to "hide the goods.")
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.
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.
