I've developed preeclamplsia in both pregnancies now and keeping the baby in means that I push my body to absolute breaking point and it just gives up and tries to dispel the baby early.
Or ur baby just might be ready my son was born four weeks early an was very healthy...
Sometimes, it's just your body not able to hold on to baby. Sometimes, there is something wrong with baby that has nothing to do with how mom took care of herself. There are behaviors that make it more likely for a baby to be born early, but there are also things that happen that also read out of our control.
I never smoked and I take great care of my body and I went into preterm labor My doctor said there isn't a reason for it sometimes. It just happens.