Hi actually it's a myth or say coincidence. But when they teeth they will have discomfort so they keep putting their hands inside their mouth leading to stomach infection again even if they dont teeth they put theirs fingers inside. So its nothing but coincidence.

It is not necessary that all the babies will get motions and usually if they happen they happen for very short span when specially nearing 6 months if you baby is having loose motion now when she is 1 year old already you will need to see a pediatrician