Weeks 21 - 24
Though your baby has no body fat at this point, it will gain more weight in the next few weeks, and by week 25, it will weigh almost twice as much. The motions, or "quickening," are increased leg and arm activity because of muscular development. Your baby's respiratory system is still immature and requires much more development. As your baby swallows amniotic fluid, its body will absorb the water from the fluid and the rest will go into its large bowel.
Your baby is approximately 10-11 inches from crown to rump and weighs 15 ounces. Though you are aware of your baby's movements, it may be a few weeks before someone else can feel these movements by putting a hand on your abdomen. Your baby is most active in the early mornings and after a nightly meal. The sugar content in some foods usually gets her moving! Your baby is growing steadily and will gain more than six ounces this week.
Blood vessels develop in his lungs, and her plugged nostrils begin to open. By this week, his hearing will be developed enough to respond to outside sounds and voices, and she may jump at sudden noises. Capillaries are starting to develop underneath her skin, giving her a more pinkish color. Her hiccups will become stronger and more frequent in the coming weeks. They do not bother him in any way or cause her discomfort.
Your baby is approximately 12-13 inches long and weighs 1.25-1.5 pounds. She still has no fat on her body yet, but her arm and leg muscles are well developed. Her eyelids are sealed, but she makes facial expressions: frowning, squinting, and pursing her lips. Her nostrils are opening and preparing to draw air into her lungs. The alveoli ("air sacs") in the lungs are forming, but not enough that she can breathe outside the womb.