Warming Breast Milk

Hello Mommies,

I am a new mommy, nursing my 3 week old. I have been both pumping and putting baby to breast. My pumped milk I store in the fridge. My question is, how best to warm the breast milk from the fridge? I have been pulling it from the fridge to sit for an hour, slowly warming to room temperature. Am I ruining my milk by doing this? So far baby has been drinking it. My concern is if I am ruining the nutritional value of my milk or if I am possibly causing bacteria to grow? Any advice would be greatly appreciated.