Your baby is growing stronger by the day. You can feel that for yourself as those first timid flutters become more pronounced pokes from her busy little feet and hands. She can touch her own face, and she may be looking for her thumb to suck.
Your baby is now about five inches long—that's not quite as long as a ballpoint pen—and her body systems are in good working order. Her circulatory system and urinary tract are functioning, and she is inhaling and exhaling amniotic fluid as she learns to breathe.
Pink nipples are forming on her chest, and your baby has mammary glands even if she's a he. If your baby is a girl, her ovaries are busy developing tiny follicles. She will have six million eggs or so at this point in your pregnancy, but that number will fall to about one million by the time she is born.
In the coming weeks your baby-to-be will be going through a new kind of growth spurt. Up until this week, her developmental milestones have centered on various organs and body systems beginning to function and then maturing. Now her body will start filling out by adding fat tissue. Fat is important for a variety of reasons. First, fat tissue helps your unborn baby insulate her body and regulate her body temperature. In her cozy home in utero, your baby's temperature is being controlled for her, but once she's born her body will need to perform that job on its own. Her fat tissue will help regulate her temperature and also store energy she'll need now and once she's born. In fact, a newborn weighing about eight pounds at birth will have more than five pounds of fat on her body.
Another side effect of adding bulk is that your unborn baby will look more and more like a newborn in each ultrasound image. Her cheeks will lose their wrinkled appearance and develop characteristic baby chubbiness.
Her face is looking more babylike for other reasons, too. Her eyes are almost in their final position and they begin to move under her eyelids. On either side of her face, her ears are beginning to function and can detect sound. Her ability to hear will continue to improve as she grows.
While you won't be able to see your baby-to-be's face except during an ultrasound, this week you might be able to feel another development—your baby kicking. Each week, she's adding fat and muscle and become stronger, so her kicks will become stronger. Keep in mind, she still only weights 3-1/2 ounces so her kicks might only feel like a flutter to you. Even though this doesn't seem like much weight, if you put it in perspective, your baby has been doing plenty of growing. For example, she's more than doubled her weight in the last two weeks, and by the end of this trimester she'll more than quadruple her weight by week 28 she'll weigh in at two pounds.
Adipose tissue: Another term for fat tissue.
Images courtesy of the American Institute of Ultrasound in Medicine (AIUM.org).