Your baby is almost fully formed now. Although she weighs just under two ounces, that will change rapidly in the weeks ahead. She'll soon be much longer than her current three or four inches. She now has a recognizable neck, and her head sits up a bit from her chest. Because her head has grown, her eyes are closer together over the bridge of her nose.
As her arms and legs continue to lengthen, she'll put them to good use. Your baby might move hundreds of times a day in her secure, thick-walled bedroom. A fine, downy hair called lanugo is growing over her body to protect her skin; it will stay there until it starts to disappear a few weeks before her birth. Your baby is also developing hair on her head, as well as eyelashes and the first hint of eyebrows. Her eyes are still firmly shut, however, and won't open until approximately 23 weeks.
The big news this week? Your baby-to-be's gender is no longer a mystery. Differentiation of male and female sex characteristics, which begins at the ninth week, is complete by week 14. Still, you might have to wait a few weeks to find out whether you're having a boy or a girl. Even if you do have an ultrasound, the sonographer might not be able to determine the baby's sex during an exam at this age, but in a few more weeks, you might be able to find out baby's gender.
One development you'll have no problem seeing during an ultrasound at this time is happening deep inside your baby-to-be's skeleton. All along his frame, connective tissue is turning into bone. This complex bone formation process, called ossification, begins in utero and doesn't really finalize until well into your child's life and even into adulthood. Bones need to be somewhat malleable in order for your baby-to-be to continue to grow now, and after he's born. Several layers of both inorganic and organic substances have to come together to help make bones form, grow and harden. You'll be able to see these developing bones grow brighter (whiter) on the ultrasound as they become larger and harder.
Advancements in his brain are also making for changes you might see on an ultrasound. He's now able to move his facial muscles to make grimaces, grins, frowns, or even a squint. Although his face might look like he's responding to emotions, he's simply trying out his facial muscles.
One reassurance to moms this week: Now that your first trimester is over and you're a week into your second trimester, your chances for a miscarriage have gone down dramatically. The concern for a miscarriage is greatest during the first few weeks of development. Now that your baby-to-be is fully formed, the chances of miscarriage decrease.
Ossification: The hardening of fibrous tissue into bone.
Images courtesy of the American Institute of Ultrasound in Medicine (AIUM.org).