How your baby's growing: Head to bottom, your baby's 3 1/2 inches long — about the length of a lemon — and weighs about 1 1/2 ounces. Her body's growing faster than her head, which now sits upon a more well-defined neck. By the end of this week, her arms will have lengthened and will be in proportion to the rest of her body. (Her legs still have some growing to do, though.) She's starting to develop an ultra-fine, downy covering of hair all over her body (called lanugo). Her liver starts secreting bile this week, a sign that it's already functioning properly, and her spleen starts contributing to the production of red blood cells. She's also producing and discharging urine into the amniotic fluid, a normal process that she'll keep up until birth. You still can't feel your baby's movements, but her hands and feet (which are now half an inch long) are more flexible and active. Thanks to brain impulses, her little facial muscles are getting a workout as she squints, frowns, and grimaces. She can grasp now, too, and she may be able to suck her thumb.