Jackson now weighs about 2 1/2 pounds (like a butternut squash) and is a tad over 15 inches long from head to heel. His muscles and lungs are continuing to mature, and his head is growing bigger to make room for his developing brain. To meet his increasing nutritional demands, I'll need plenty of protein, vitamins C, folic acid, and iron. And because his bones are soaking up lots of calcium, I need to be sure to drink milk (or find another good source of calcium, such as cheese, yogurt, or enriched orange juice). This trimester, about 250 milligrams of calcium are deposited in his hardening skeleton each day.