When I had my babies, someone from our church always used takethemameal.com so I could put in any info about what I liked, didn't like, or dietary restrictions. You could always ask the person you're cooking for what they would like since everyone is different.
Both of my babies were sensitive to dairy, which was unfortunate because I love dairy! When I was pregnant I could have dairy, but limited sweets or carbs, & nursing- carbs & sweets, but no or limited dairy. And I went directly from nursing 1st to being pregnant again so I've had dietary restrictions for the last 2.5 yrs straight! So pizza, cheesecake, & ice cream were off limits in both cases, whether nursing or pregnant. I'm hoping to have a small break to eat all I want between this one & next!
After baby #2, my hubby made spaghetti, which is my least favorite meal, one night. Then the next day, a family from church lovingly brought a meal to us. It also was...spaghetti.
But I thanked God for it anyways! But this is probably a safe dish all around.
Now, all of this to say, for someone who just had a baby, I would probably bring a casserole dish. And dessert!!