The Baby's Exact Size
Your baby begins week 17 measuring 5.12 inches from crown to rump, and, by the end of the week, she'll grow another half-inch. She's also gaining weight very rapidly-- she'll grow from 5 ounces to 6.7 ounces during this week. Remember that, at this age, a baby's length is measured from the top of her head to her butt, so she's actually a couple of inches longer than the standard measurement.
A 17-Week-Old Fetus is the Size of...
It's not easy to envision your baby based on numbers alone, but comparison can help you to visualize her. Your baby is not about as long as your hand (including your longest finger) and weighs about the same as a turnip or a large onion. Due to her rapidly increasing size, she is inching closer to viability as each day passes.
What the Baby Looks Like
At 17 weeks, your baby definitely looks like a baby. Her eyes and ears are now in their proper positions, she can move her joints, and she has functioning taste buds and sweat glands. If you could peek inside right now, you'd see her fluttering about, kicking, jumping, twirling and even sucking her thumb. By this point in your pregnancy, you're likely feeling all of these movements.