It's because there will be sudden atmospheric pressure difference between stomach when they are in and outside tummy. And... due to too much air..baby will feel pain. Any insects or anything may enter. For that reason elders use to ask to cover. If baby is uncomfortable...then no need.

My grandma always asks me n my lil one to keep ears closed...,, old <u>myths</u>

Not necessary. only during cold winters.&nbsp;