What factors would risk me out of a home birth?

Any complications. Home delivery is a pretty hot topic. If you have any medical complications, we would recommend you deliver at the hospital. If the baby is in an unusual position, you may be better off at the hospital. Also remember that you can work with your doctor to make your hospital experience less "hospital like" as well.
Depends on the case. Many deliveries go smoothly ; might do fine at home or in a birthing center but you know this after the fact. In the us between 20-30% of deliveries are by c-section, often as an emergency ; at least 10% of newborns require some specialty care at birth.Centers designed to give you the midwife/minimally invasive experience with physicians ; operating rooms on standby are the safest choice.
Twins, prev. C/S. Although home birth is a much-desired event for some women, there can be some unforeseen risks, even in a singleton pregnancy. However, patients with a previous c-section, multiples (twins, triplets), and breech presentations are examples of pregnancies better suited for hospital delivery.