ive been told that even though youve had laser sessions done, you can get a sudden growth of hair when youre pregnant... how weird because isnt the hair follicle supposed to stop making the melanin?

I would suggest start seeking laser treatment after pregnant.
There are lots of things get changed after pregnant...

Neither LASER nor electrolysis can treat hairs you don't have yet.

The hair a woman may start growing after events like Pregnancy, menopause, drug interactions, or other imbalances are situations where changes in the body cause previously empty follicles to start growing hair when they never had grown hair before. In this case, there was nothing for an electrologist to treat, and no pigment for the laser to key on, unless the person had freckles, or a tan.

Short of treating empty follicles on the off chance that they may start growing hairs years later, what could anyone even try to do for this?

Rest assured, you are not talking about hair growing from the follicles that have previously been treated and have somehow regenerated themselves. A properly treated follicle has nothing but thick tissue in the indentation.

read my short article about laser hair removal during pregnancy
http://laserhairemoval.blogspot.com/2006/01/laser-hair-removal-during-pregnancy.html

Due to hormonal changes hair can grow event though you have laser hair removal before..

It seems to be more common to have reduced facial and body hair growth during pregnancy, and increased growth a few months after the birth. However I have encountered the occasional unfortunate woman, who experienced significantly increased growth during pregnancy. It is not common though, from my personal experience.

ANY event that causes a change in a woman's hormones can lead to new hair growth, and, or thicken the hairs one already has.

This means that not only can the start or ending pregnancy cause hair, but beeing stressed out with worry, or anxiety for 2 weeks or more can do it as well. (now you have something else to blame on that jerk )