Certainly, emergency room doctors like Dr. Josyann Abisaab see children who have swallowed serious choking hazards. As a parent, it is very important to child-proof the house and to check each room for choking dangers. Make sure, when you purchase toys, that you only purchase items that are age-appropriate.
Obviously, if you have older children, this poses a problem. Keep toys with small parts far out of reach of small children and teach your older children about the dangers that their toys can pose to their small siblings.
One interesting idea is to purchase a parts tester which you can get at most toy stores for only a few dollars. These will test objects for you to see if they are small enough to pose a choking hazard.
When you enter a room, look around for choking hazards. Make sure you know CPR and that any caregivers that you hire or take your children to know CPR as well.