A spontaneous abortion (also known more commonly as a miscarriage) is when a pregnancy can no longer be maintained and the fetus dies. By definition, a miscarriage must occur before 20 weeks of gestation for it to be called a miscarriage. Unfortunately, some pregnancies have complications even in the 3rd trimesters. When these complications result in fetal death, it is called a stillbirth. The good news is that the further you get along, the less likely that you will have one of these catastrophic events. Thus, statistically, you are much more likely to have an uncomplicated birth today than 5 months ago.
Since you used the term incomplete abortions, I will comment again on the miscarriage definitions, which can be quite confusing.
1. Spontaneous abortion - loss of the baby before 20 weeks (cervix dilated and fetus expelled
2. Threatened abortion - bleeding
from the uterus when the fetus is still viable and cervix closed, this does not always result in loss of the baby
3. Inevitable abortion - bleeding from the uterus, cervix is dilated fetus still in uterus
4. Incomplete abortion - bleeding from the uterus, cervix dilated, part, but not all of the products of conception still present.
The best thing for you to do is to keep your scheduled appointments with your OBGYN as your due date approaches. This way you can be sure to do everything you can to have a healthy delivery. Good luck.