The hospital should provide diapers, wipes, a onesie, hat, and blanket for baby. I packed WAY too much. All I used was the going home outfit for my son (I wore the same clothes home that I wore to the hospital because I didn't want to ruin any other clothes lol) and snacks. If you plan to formula feed, maybe pack bottles, formula, etc; I'm sure the hospital would provide that stuff if you need it. I breastfeed, so I'm not sure! If your hospital doesn't let you eat during labor or have a room with food that you're free to get at any time, (mine didn't) I would pack lots of snacks and drinks. Pack extra clothes for your DH in case your hospital stay is a few days. Oh- phone, charger, and camera! That's all I needed, but you may also want to take lotion, chap stick, deodorant, (I hope I took that!) etc; If you plan to shower, take extra clothes (my hospital provided shampoo, conditioner, deodorant, soap, toothpaste, toothbrush, mouthwash, baby powder.) I didn't shower because the showers are so tiny and the water only goes to 80 degrees...way too cold for me. lol
I was required to wear a hospital gown during my stay...maybe take a pillow though? I wouldn't take a favorite blanket, it would likely get blood on it and possibly ruined. (I had a vaginal birth with 2nd degree tears...I bled a lot for the first few days) Oh, and soft toilet paper or sanitary wipes! The hospital has toilet paper that feels like sandpaper!