Since a few ladies here were questioning their breasts ~ disliking bras, running, etc. I thought I'd start a new thread to discuss the topic.
Genetics does influence our size. Being overweight or pregnant typically makes our breasts larger. Being underweight and post-pregnancy makes our breasts smaller.
I was a C to D cup as a young lady. Became a triple D when pregnant ~ down to a DD while nursing my girls ~ then down to a B cup for a few years (as I was 10 lbs underweight). I'm now a C cup, and that's just fine with me

. The C is way better than DDD!!
All of that said, large breasts run in my family. Ya-hoo! Nursing did teach me to relax a whole lot towards my breasts, so that was a very good thing for me. It also taught me that getting accurately sized (w/ measuring tape by professionals) is crucial! A local dept store sized me a 34B, then changed to 34D a minute later

. A trip to Victoria's Secret to get accurately sized was definitely worth the money!
Trying on bras, activity sports tops, etc
is also crucial.
Different styles (of the same size and/or manufacturer)
fit differently. It seems that most of the "cool styles" and lots of variety are made for smaller chests. Imo, A's and B's have it made w/ lots to choose from

.
Just my opinion....