What causes yellow vaginal discharge before menstruation?

Yellowish vaginal discharge before menstruation may be caused by hormonal changes, bacterial vaginosis, or other reasons. 1. Hormonal changes: Female estrogen levels fluctuate significantly before menstruation, which may increase vaginal secretions. If the discharge is not promptly expelled, it may appear slightly yellowish. However, if there is no odor or other clinical symptoms, this is considered a normal physiological phenomenon. 2. Bacterial vaginosis: This is usually caused by anaerobic bacterial infection, leading to an imbalance in the vaginal microbiome. It results in yellowish vaginal discharge, often accompanied by a foul odor and symptoms such as vaginal itching. A routine vaginal discharge test can confirm the diagnosis.