I was reading about how the abortion drug works & can remember reading that if you take the X amount of the pill (the normal contraceptive one) it will have the same effect that the morning after pill does. I guess it would carry some risk if taking it while pg & not realising but I don't think its a yes you will m/c if you take the pill while pg. There are plenty of people who fall pg whileon the pill & carry a baby to term. My sister for one.

As for it being less effective when your sick I guess it could be less effective when you have Diahorrea but the reason it would be less effective when vomiting would be because of the risk of throwing it up before your body had absorbed it.