Usually I will leave the frozen bag in a container of water and leave it in the fridge to thaw on its own. And then when my mum needs to feed she just pour it into bottle and warm the bottle up. This way I find it's safer for me because I'm not sure why, some bags may leak. (Maybe I put too much milk in the bag or I accidentally dropped the frozen bag so it cracked?) And I'll know when I see the container water turned cloudy.
If urgent I will run the frozen bag under running water and when it's soften abit, "break" it into smaller pieces for faster thawing under the water. Once into smaller pieces to fit into the bottle just dump all inside and warm.
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