Does recursive hashing weaken properties of a secure hash algorithm?

Specific example of mine concerns the probability of collision, where I have two plain texts A and B that I want to hash using MD5.

Given the secure hash function H and the following:

A' = H(A)
B' = H(B)
A'' = H(H(A))
B'' = H(H(B))

is the probability of A'' and B'' colliding higher than that of A' and B'?