Though it’s tempting to stick a bottle in the microwave when your baby’s crying for his milk, it’s not a good idea. Firstly, microwaves don’t heat evenly, which means that despite those first few drops of formula passing the wrist-test, there could still be hot spots that might burn your baby’s mouth. So if you do heat it in the microwave, give it a good shake and test the temperature again before giving it to your baby.
Secondly, microwaving the bottle could also cause potentially harmful toxins to leach from the plastic into the formula, according to some experts. This is because the quality of plastic used for bottles varies widely, and not all bottles are even microwave-safe.
The best way to warm your baby’s bottle is by running it under hot water from the tap. Or, even better, fill a coffee mug half-way with hot (not boiling) and warm the milk by putting the bottle in the hot water for a minute.
You may find that you don’t need to heat the bottle at all. Some babies actually prefer their milk at room temperature.