Why does women middle finger shrink during their period?

During menstruation, hormonal changes, particularly fluctuations in estrogen and progesterone, can lead to fluid retention and swelling in various parts of the body, including the fingers. Additionally, changes in blood flow and inflammation can affect the joints, potentially causing temporary swelling or a feeling of tightness. As the period progresses and hormone levels stabilize, any swelling typically subsides, leading to a return to normal finger size.