Doctors at Johns Hopkins are studying how much exercise is OK for pregnant moms and their developing babies, according to an article written by my colleague Meredith Cohn.

Cohn writes that data from the study could help doctors customize workout schedules for pregnant women in various states of fitness.

Not too long ago doctors used to tell all women not to exercise when they became pregnant, but that advice has changed, said [professor and vice chairman of the department of gynecology and obstetrics for the Hopkins School of Medicine Anthony] Satin and Dr. Linda Szymanski, a fellow in maternal fetal medicine helping conduct the research. But there still is little data about what's too much for the elite athlete verses the couch potato and those in between. Satin said much is based on "opinion and common sense."

Doctors generally advise pregnant moms get 30 minutes of exercise a day.

But the advice is based on recommendations from government and groups such as the American College of Sports Medicine that non-pregnant people get such exercise. And it's filled with notes of caution for those who are just starting and those with certain conditions. The college suggests seeing a doctor first, starting slow and stopping when there's pain or bleeding — advice Satin doesn't dispute.

What kind of exercise did you get while pregnant? (I mostly practiced prenatal yoga.)