Does Stress And Exercise During Pregnancy Lead To Miscarriage?

a friend of mine was 5 months pregnant and just had a doctors appt and discovered the baby was dead. they found out a month ago that the baby s heart wasnt as developed as it should be. They had meet with a surgeon that assured them that he felt the baby would be fine. She was doing great until last Thursday she had been on her feet a lot, was under a lot of stress and had been in the heat a lot that day. Her feet were terribly swollen. Could this be why she lost the baby?