Extreme stress might cause early labor ... maybe. It will not just reach out and stop the fetus' heartbeat at that late stage.
It can cause miscarriages in early pregnancies, its something to do with when we're stressed we release enzymes into the blood stream,
i was very stressed last year and 5 months pregnant but my baby was fine, it could end up in premature labour if badly stressed though
It really depends on the stress and how it's affecting her physically.
I am 35 weeks pregnant today, I've been under a LOT of stress the last couple of months...having issues with my teenage daughter and more recently finding out that my mother has cancer and only a few months at most to live. Additionally dealing with 4 cihldren, I have been under a lot of stress, but my baby is doing just fine.
If you are under more than moderately elevated stress, you can always talk to you doctor about your options for stress relief.