Why are yeast infections more common before my period?

Yeast infections are more common during the luteal phase of the menstrual cycle (the stage after ovulation, leading up to the first day of your period).

Though the mechanisms aren’t clear, researchers attribute this to the elevated levels of estrogen, which could support the proliferation of C. albicans by increasing glycogen (stored carbohydrates, which are a nutrient for the yeast) in the vaginal cells, suppressing vaginal immune cell function, and/or promoting the transition of Candida from its yeast to hyphal forms.

This could also explain why yeast infections are more common during pregnancy and post-menopausal hormone replacement therapy.^[1]