24 Weeks Pregnant

At 24 weeks, the fetus's own bone marrow begins to help the placenta make blood cells. Your baby's lungs are developing, too. They begin to make a substance called surfactant, coating the tiny air sacs in the lungs. After your baby's birth, surfactant will keep the sacs from sticking together and collapsing when your baby exhales.

As you know, your body is doing some remodeling to accommodate your growing baby. One result may be a sore, stiff, aching back. One source of back pain is strained muscles caused by the changes in your body and posture. The curve of your lower back has increased as the baby's weight presses down. Your center of gravity has slid forward, too.

Your ligaments and joints may also be feeling the strain. During pregnancy, a hormone called relaxin causes them to loosen and stretch.

Try these tips to soothe your sore back:

• Use a heating pad or hot water bottle.
• Alternate heat packs with ice packs.
• Get a professional prenatal massage.
• Stretch — on your hands and knees, slowly round and arch your lower back.
• Exercise to build strength, improve posture, and loosen muscles.