Katharine McPhee shows off incredible post-baby body just five weeks after welcoming son Rennie

Katharine McPhee is 'ready for spring' in Valentino outfit... five weeks after welcoming son Rennie

Katharine McPhee, 37, and David Foster, 71, step out for the FIRST TIME with son Rennie

Katharine McPhee drapes svelte post-baby body in sleek double-denim look out in LA