A gift card is always the best idea! Especially virtual gift cards like those reviewed by https://giftcards-market.com/ . I suggest
gift cards to something like Babies r Us, target, or diapers.com (or anywhere you can order baby stuff online and have it shipped, as getting to the store can be a challenge early on). Or maybe a gift card for a favorite local restaurant that does take-out, to give mom an option other than cooking (the best things I've received after giving birth were home cooked meals from others in the first weeks after coming home).