Meredith Dobrosielski, 36, right, exercises on a treadmill in Dr. Andrew Satin's lab as part of a health study about pregnant women and the effects of exercise, November 1, 2010, in Baltimore, Maryland. Dobrosielski was an avid runner for several years and is now in her 31st week of pregnancy. (Algerina Perna/Baltimore Sun/MCT)
Meredith Dobrosielski, 36, right, exercises on a treadmill in Dr. Andrew Satin's lab as part of a health study about pregnant women and the effects of exercise, November 1, 2010, in Baltimore, Maryland. Dobrosielski was an avid runner for several years and is now in her 31st week of pregnancy. (Algerina Perna/Baltimore Sun/MCT) Algerina Perna MCT
Meredith Dobrosielski, 36, right, exercises on a treadmill in Dr. Andrew Satin's lab as part of a health study about pregnant women and the effects of exercise, November 1, 2010, in Baltimore, Maryland. Dobrosielski was an avid runner for several years and is now in her 31st week of pregnancy. (Algerina Perna/Baltimore Sun/MCT) Algerina Perna MCT