Roughly one-third of the women running in the New York City Marathon this Sunday in the professional field also have children, according to the New York Times. Unknown, however, is how many are currently pregnant. But running — around the block or in a marathon — with a bun in the oven is possible.“I’ve run through three pregnancies up until the day I had my kids,” elite runner Clara Horowitz Peterson told the Times. Running even has an important part in her family history: she went into labor with her second child while on a run. This up-to-the-minute planning is more common than you’d think, as elite female athletes often consider corporate sponsors and Olympic timing when weighing the timing of a pregnancy.Peterson qualified for the 2012 United States Olympic marathon trials only four months after the birth of her second child. While running during pregnancy is perfectly healthy, Peterson notesedfellow trailmates can’t help but share their opinions — be they negative or positive.Alas, maternal health expert Dr. Sheeva Talebian told Women’s Running Magazine that running while pregnant is simply a matter of listening to your body. Like any exercise, make sure you can talk while running and keep from overheating.