Mild exercise throughout pregnancy may reduce the discomfort associated with pregnancy and result in a speedier, easier birth, according to a recent study.
(A) may reduce the discomfort associated with pregnancy and result in
first bit makes sense , exercise may reduce the discomfort ,but the second ,exercise may result in speedier, easier birth,doesn't.
imo incorrect
(B) may reduce the discomfort associated with pregnancy, with the result
seems the result is assured rather than that it may happen
same as A
(C) may cause a reduction in the discomfort associated with pregnancy and as a result
seems bit wordy but may cause "a reduction....and as a result a speedier, easier birth" makes sense
(D) might lead to a reduction in the discomfort associated with pregnancy and as a result
might should be "may" incorrect
(E) might reduce the discomfort associated with pregnancy and resulting in
same as D
furthermore "reduce ...and resulting" parallelism issue
IMO C