Meredith Dobrosielski, 36, exercises on a treadmill in the lab of Dr. Andrew Satin (pictured) as part of a health study about pregnant women and the effects of exercise. She has been an avid runner for several years and is now in her 31st week of pregnancy. Before she begins the workout, she's hooked up to a fetal monitor which also takes the mother's heart rate. Today's exercise is of moderate intensity: a 30-minute brisk walk.
Baltimore Sun photo by Algerina Perna