17 weeks

your baby is hitting the height chart at five and a half inches long (remember, that's crown to rump) and weighs about five ounces (the weight of that boneless chicken breast you're making for dinner). And now for the skill of the week (drum roll please…): The art of the yawn has been mastered by your baby (someone's sleepy!). In fact, you might catch a glimpse of that adorable yawn if you're getting an ultrasound this month. You'll also catch a glimpse of all the fetal movement your baby's doing — twists, rolls, kicks, and punches. And would you believe your baby is finally big enough for you to start feeling those movements now (or anytime in the next few weeks). So get ready!
Something you won't see on the ultrasound, but you'll know is in working order, is your baby's nervous system, which is maturing rapidly at this time. Nerves, now covered with a substance called myelin (which speeds messages from nerve cell to nerve cell), are forming more complex connections. And those in the brain are further specializing into the ones that serve the senses of touch, taste, smell, sight, and hearing. Talking about hearing, your baby's is growing more acute, making your little one more conscious of sounds that come from inside your body (which means you could both be listening to each other hiccup — a skill that your baby has by now).