Baby Bottle Basics

If it's formula and you're just taking the chill off by placing the bottle in warm water for a minute or two, that's fine, says Victoria Regina, a registered nurse with an OB-GYN practice in Newburgh, New York. The formula should still feel cool when you test it on your wrist. Be sure to refrigerate it within 15 minutes and use it at the next feeding, or within 24 hours. Don't reuse formula after getting it truly warm, however (like if you heat it to body temperature or higher). The higher heat will promote bacteria growth and could make the formula less nutritious if reheated.

Breast milk doesn't have to be refrigerated in this scenario either, according to Dr. Sears. You can keep it out at room temperature (66 to 72 degrees F) for up to 10 hours.