Development Week 17
Your baby is now 5.12 inches (13cm) and 4.97 ounces (140 grams), and is weighing more than the placenta. He is starting to develop brown fat deposits under the skin, but no other new structures have formed. During the last trimester your baby will add more layers of fat to his body for warmth and protection. The baby may start to respond to loud noises outside the body.
A Whole System
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.
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.
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