Was in garage (garage door open) when car was started and smelled strong exhaust. Was in there for about 30 seconds and 23 weeks pregnant - problem?

Pregnant. I would say no problem however if you are worried please ask your obgyn at your next check up. Recent studies have shown that both mom and baby benefit from walking outdoors. The tiny bits of pollen etc that you breath in help strengthen the baby's immune system and wards against allergies.
Probably not. The fetus is more susceptible to carbon monoxide but the exposure you describe is unlikely to be enough to cause any harm. Generally there would need to be more prolonged exposure in an enclosed space to cause problems.