The asymptotic behavior of # n (d;) # n (d:) &1 and P n (x, d;) P &1 n (x, d:) is studied. Here (# n (.)) n are the leading coefficients of the orthonormal matrix polynomials P n (x, .) with respect to the matrix measures d; and d: which are related by d;(u)= d:(u)+ N k=1 M k $(u&c k ), where M k are positive definite matrices, $ is the Dirac measure and c k lies outside the support of d: for k=1, ..., N. Finally, we deduce the asymptotic behavior of P n (c, d;) MP n *(c, d:) when d;(u)=d:(u)+M$(u&c), with M a positive definite matrix and c outside the support of d:.