So when it comes to bra sizes the band circumference matters more than the letter afterwards aka bust size, here is a chart it will help you understand 28D is basically A cup while my moms 34H is an actual H cup(the smallest the underbust the bigger the cup but that doesnāt equal volume)
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So breasts are made of fat and soft tissue, the tissue is being build by the hormones we take Estrogen and progesterone afterwards. So after the tissue is done building up because of hormones the fat should start being redistributed in a female pattern, so your genetics aka how youāre genetically programmed to store fat(trunk area and lower body for ex) will depend on how your body looks after youāve basically replicated a natal female puberty. So just looking at my mom who has high fat % in her hips and breasts I should be genetically predisposed to also store more fat in those areas. Though I donāt have hormonal cycles with high enough stable E levels it should give me a good breast volume