15 weeks

Continuing the march towards normal proportions, baby's legs now out measure the arms. And, finally, all four limbs have functional joints. Your fetus is squirming and wiggling like crazy down in the womb, though you probably still can't feel the movements.

Your growing baby now measures about 4 inches long, crown to rump, and weighs in at about 2 1/2 ounces . They're busy moving amniotic fluid through her nose and upper respiratory tract, which helps the primitive air sacs in their lungs begin to develop. Their legs are growing longer than their arms now, and they can move all of their joints and limbs. Although their eyelids are still fused shut, they can sense light. If you shine a flashlight at your tummy, for instance, they're likely to move away from the beam.

There's not much for your baby to taste at this point, but they are 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.")

Information from BabyCentre and The Bump.