Your baby’s beginning to develop fat this week, and you might be developing some new aches, pains, and general itchiness! It’s all here in three things to expect during pregnancy week 17.

1. Fat Forming

Measured from crown to rump, your baby's about 5 inches long this week and weighing in at about 4 to 5 ounces. And your little one is committed to plumping up: this week she or he is beginning to form body fat known as adipose, essential for keeping warm and regulating metabolism. By the time you deliver, it's this fat that will make up 2/3rds of your baby's body weight.

2. Development News

Your baby's now the proud owner of a pair of fully formed ears, and will continue to sharpen his or her hearing in the coming weeks. With baby's heart now regulated by the brain, it's running at a consistent (and rapid) 140-150 beats per minute. Tiny fingerprints are beginning to form on tiny fingers. To support all this development, the umbilical cord is getting thicker, stronger, and longer. Go, baby!

3. And Now to You, Mama

Are you feeling any twinges of pain in your legs, mama? As your baby and uterus grow, they're putting pressure on your sciatic nerve, the largest nerve in your body which runs from your uterus to your legs. You might also be noticing that your breasts and belly are increasingly itchy, as your skin is stretched over your growing shape—which, unfortunately, can result in stretch marks. If you're concerned about these harmless but unsightly marks, aim to keep your skin well moisturized and nourished with product designed to ease stretch marks. We're not sure there's a moisturizer that can really live up to its promises, but better to feel like you're doing something about it, right? Plus the moisturizing can help with the itchiness.