natural abortion?

Disclaimer: I do NOT mean taking herbs or some other at home means of giving yourself an abortion. I only use the term natural abortion because I'm not sure if there is an actual name for what I'm wondering. I am wondering if it is possible for your own body to decide to abort a pregnancy. I know that if you are sick or stressed, your body may decide it is a bad time to have a baby, and you may not ovulate, or have delayed ovulation. I also know that quite a lot of early pregnancies are made s carried due to the embryo not being viable for some reason or fails to implant correctly. What I want to know is, is it possible for any reason (stress or illness for example) for your body to devide it's a bad time for a baby, and it chooses to abort an early pregnancy of a perfectly healthy and correctly implanted embryo? I'm ttc, so I really hope it's not possible, but I'm not sure.