The hormonal changes that occur around a woman's period are often enough to trigger yeast overgrowth. Women often get vaginal yeast symptoms for a few days prior to their period. A mild vinegar was of the nipples after feedings (1 tablespoon vinegar in 1 cup of water) might help. However the severity of her symptoms may require further investigation into a subclinical (it's there but no symptoms) yeast overgrowth. Marie Davis, RN, IBCLC