When your wife/partner is up during the night feeding or changing the new baby, you can lend her physical and emotional support by getting up too. Even if you do it just to give her some adult company during those long dark hours of night when baby is awake, she will appreciate you making the enormous effort to get up. You don't have to do it every time she is up. In fact, you might agree that you will get up once every second night for a full feed session and you will change/prepare the baby, or you might agree to be up every second time the baby awakes. Whatever you both agree on, it gives your partner a relief from the lonely solo efforts she endures.