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 9th 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.
Terms to Know
Ossification: The hardening of fibrous tissue into bone.
Important Information About Your Pregnancy
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Images courtesy of the American Institute of Ultrasound in Medicine (AIUM.org).