Her Asics laced up and her water bottle at her side, Meredith Dobrosielski stepped onto the treadmill for a robust half-hour walk.
For the Towson runner, this wasn't just any trip to the gym. The session took place in a lab at Johns Hopkins Bayview Medical Center in Baltimore. And each step offered information on the impact of exercise on her fetus. Dobrosielski is about 8 months pregnant.
Doctors expect the information collected to fill in some gaps in the data on how much pounding is OK for a developing baby. Eventually, they hope to be able to develop personalized workout schedules for women in different states of fitness.
"We do know that not only can exercise be done, it should be done," said Dr. Andrew J. Satin, professor and vice chairman of the department of gynecology and obstetrics for the Hopkins School of Medicine. "But the level of fitness should impact the individual's prescription."
Not too long ago doctors used to tell all women not to exercise when they became pregnant, but that advice has changed, said 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."
They believe research is limited because doctors fear testing pregnant women. But nine months into the study, there have been no adverse reactions. As a precaution, the hospital's labor and delivery area is close by.
About 60 women in their third trimester of pregnancy take turns on the treadmill. Some are regular runners and others are sedentary. Everyone takes a moderate walk, and the regular runners also run until they hit their peak capacity but don't linger there. Several measurements are taken over the sessions from fetal heart rate and blood flow to the womb to fetal movement and amniotic fluid levels. The fetuses are examined by ultrasound before and after treadmill work.
Over time, the doctors plan to measure the impact on fetuses; partner with biomedical engineers to develop new ways to monitor the fetus, perhaps wirelessly during exercise; and collect long-term data on the pregnancy outcomes. The treadmill tests are the first step and some solid data should be available in a couple of months.
Doctors and groups such as the American College of Obstetricians and Gynecologists and the American Pregnancy Association now give blanket advice to pregnant women to get 30 minutes of exercise a day.
Potential benefits include improvement in general health and a decreased chance of gestational diabetes and hypertension, among others. Also, these groups say, that labor, delivery and recovery can be easier.
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.
He added that doctors do know driving up a heart rate and maintaining it there for too long can cut off blood flow to the fetus. Getting overheated and dehydrated are also problems. Joints also can become lax and balance may be off, so some exercises should be avoided, such as street biking late in pregnancy. Contact sports, horseback riding and downhill skiing also may cause injury from blows or falls.
But he and others say not everyone has gotten the message that exercise is beneficial.
It was a big change in 2008 when physical guidelines were published for Americans, including pregnant women, said James Pivarnik, who works with the sports medicine college and is professor kinesiology and epidemiology and director of the Center for Physical Activity and Health at Michigan State University.
He said the guidelines do indicate "that the elite runner can continue doing what she is doing for a bit, provided her health care provider is in the loop, and that she has no warning signs or other issues." But he said "boutique" recommendations are hard with so many possible circumstances.
"Pretty much the aerobic recs are the same as for anyone," he said.
Pivarnik agreed more research is needed, such as Satin's. He's now looking at how much weight lifting is good for pregnant women.
Szymanski said the incomplete data has only confused the message. "[Pregnant] women express frustration because a number of doctors give different advice. Some still tell them not to exercise, especially if they haven't been exercising."
Outdated information and myths perpetuated by the Internet still mean many women who had been exercising — up to a quarter by some accounts — stop because they fear they will harm their babies, the doctors said.
Satin said it's actually a really good time to suggest starting an exercise program. Women are more apt to take care of themselves when they are pregnant. They'll quit smoking, eat better and exercise for the sake of the developing baby and then carry over the good habits, he said.
As long as jogging is comfortable, runners can keep at it. Stationary bikes and running in a pool also are good exercises, Satin said. And walking is safe for nearly everyone. The fetuses are not "flipping and flopping," he said. In fact, the entire uterus is moving with the exercise motion, buoying the fetus.
Satin said his interest in pregnant athletes grew out of his work with women in the military who wanted to stay physically fit. He was formerly a professor and chair of the Uniformed Services University F. Edward Hebert School of Medicine in the obstetrics and gynecology department. Szymanski also is an exercise physiologist and collegiate athlete.
Dobrosielski, who is about to have her second child, said she decided to participate in the study because she wanted to help other women. She's been running "forever" and played field hockey in high school and college. An ankle injury stopped her from running after 4 months, but everyday she runs in a pool, or does yoga, lifts weights or rides a stationary bike.
She knows she won't lose as much of her fitness and will be able to return to running, even racing, quickly. Others should be able to find out what's good for them, she said.
"It's a special population and there's so little time for study," she said of pregnant women. "I felt comfortable exercising and I knew when I needed to stop. I think it's important for all women to exercise and maybe this research will convince them to do that."
Exercising while pregnant
Several medical organizations recommend 30 minutes of exercising a day for pregnant women.
•If you're just beginning or have a condition, consult your doctor. Start slow and stop if you have pain or bleeding.
•Don't get overheated, stay hydrated and take breaks.
•Your joints may be lax and your balance off, particularly in later months, so avoid unstable ground or consider a stationary bike or running in a pool.
•No contact sports, but some weight training is OK. Avoid lying on your back after the first trimester.