The weight of babies at birth ranges from 3kgs to 10kgs. What is the probability that a woman whose weight is 130kgs will give birth to a baby weighing 2kgs
3 to 10kgs ( notwithstanding the impossibility ) is a spread around (3+10)/2 kgs
so you have to decide whether 3-10 kg is normally distributed ( yes )
and whether the spread respresents one or two standard deviations
I think two
so the SD is (6.5 minus 3)/2 or 1.75
2kg is within three SD and so the chance is around 0.3% - three in a thousand
You haven't taken the mother's weight into account though PP- have you assumed it a red herring as it may well be, or do larger mums tend to have larger babies?