1 Samuel 1-3

I have heard of the similarities between Hannah's song of praise and Mary's magnificant (Luke 1:46-55). One noteworthy difference is when the singing was offered in relationship to the respective son's birth. Hannah sang after she had dedicated Samuel to service at the tabernacle. Mary sang before Jesus was born. So I wonder if Hannah's example for Mary might be an overstatement. Or could it be that Mary was dedicating her son to God's service before he was born?
Stuart