Literature has shown that Formaldehyde exposure can cause early termination (miscarriage), as well as a multiude of birth defects both developmentally and physically. I am not sure how much exposure one needs for these potential risks to occur but I know if I were in you shoes, I would absolutely refuse to be exposed to formaldehyde. Hope this helps.
The studies that I have read seem to indicate that it is safe in later pregnancy. Although it appears inconclusive during any stage of pregnancy. I would contact your dr to see what he has to say about it or see if you could take the class next semester. I am sure, however, that a lady in my A&P class dissected during pregnancy. I don't remember exactly how far along she was, however. Also, talk to your professor and he may know. I would guess that the room is very well ventilated, plus you'll be wearing gloves. Good luck with the nursing program, you won't regret it.
I would ask your teacher if you could make it up after you had your baby and explain why. Good Luck