Week 17

Your Baby's Development
At about 4.7 inches (12 centimeters) and 3.5 ounces (100 grams), your baby is still very tiny. But this week brings the development of brown fat, which will help keep your baby warm after birth. During the last trimester your baby will add more layers of fat to her body for warmth and protection.

The placenta, which nourishes the fetus with nutrients and oxygen and removes wastes, is growing to accommodate your baby. More than an inch thick, it now contains thousands of blood vessels that exchange nutrients and oxygen from your body to your baby's developing body.

Your Body
You may notice that your breasts have changed considerably since your pregnancy began. More blood is flowing to the breasts, which increases their size (many women increase one to two cup sizes) and causes veins to become visible. Buy supportive bras in a variety of sizes to accommodate your breast growth during pregnancy.