Breast volume fluctuations are associated with oestradiol and progesterone changes across the menstrual cycle

Abstract

Abstract Background:Breast volume changes across the menstrual cycle, but the relationship of this to oestradiol, progesterone and awareness of this change has yet to be characterised. Across the menstrual cycle, this study investigated relationships between breast volume, oestradiol, progesterone, and perceptions of volume change, with associated behaviour change. Methods:Fifteen women undertook saliva hormone testing bidaily throughout one menstrual cycle. Women attended six laboratory appointments across their cycle (day 2, ovulation-2, ovulation, ovulation+7, menses-3, day 2 (month two)) for 3D surface scanning (breast volume), perception of volume and behaviour change was recorded. Results:Breast volume changed by +7.3%, but up to -41.7% in one woman. Volume asymmetry increased around ovulation (5.1%). Breast volume change strongly correlated with oestradiol and progesterone, but was delayed by three appointments (left r=0.85; right r=0.95) and one appointment (left r=0.84; right r=0.84), respectively. For women whose volume decreased in follicular and increased in luteal phases (typical pattern; n=11) oestradiol decreased by 13.3%, compared to those who did not (n=4) (14.2%). Breast volume was not associated with perceived breast volume change. Conclusion: Average breast volume increases of ~one-third bra cup might not be meaningful; however, inter-participant variability was large, with up to ~1 bra cup change. As women did not accurately perceive their volume changes, measuring individuals’ cyclical breast volume would be useful for bra fitting. Volume peaked ~13 days after oestradiol and ~four days after progesterone peak. However, large variability makes it difficult to predict this; studies should take multiple samples across the cycle.