Seriously... they wont care. I mean it depends on your grades and such, but honestly, a semester like that is not going to matter at all. If you were to have taken only 2 classes a semester for 8 years and THAT is why you have a 4.0, then they would obviously not take you seriously. But if you end up taking a couple less classes a semester, they arent going to care one bit. Heck, I took ONE class in my final semester in college so that I could work part time and study for the MCAT. I received multiple acceptances and didnt get even one ounce of flak for it. Maybe if you were applying to Harvard or something, where you are competing against 15,000 applicants with absolutely perfect applications, then you would be out of luck; but for 90% of the other medical schools in this country, a little thing like that is for real no big deal.
The bigger issue will be that if you take less than 12 credits then you will lose financial aid since you will no longer be a full time student.