Does keeping your childhood hairline until 20 years old mean you won't go bald?

Certainly if you have your choice of a "normal" hair line at age 20 versus one retreating at this early age, you have a better chance of less hair loss in the future. One who has significant male pattern hair loss by age 20 will most likely go to a Hamilton Class 6-7 as years progress. BUT a normal hair line at 20 does not guarantee anything in maintaining your hair in future years. 

No, keeping a childhood hairline at 20 has no implications or meaning whatsoever. Please show the hairs to a dermatologist or hair loss physician- this is likely a normal telogen hair but he or she will confirm once they look under a microscope.

Over time, roughly 40% of women and 80% of men will experience noticeable hair loss.  This can unfortunately begin at any age. Having an excellent hairline at 20 does not indicate that one will not go bald, though it is a promising start.  If you feel like you would like more information, seek a consultation with a hair restoration specialist. Best of luck!