How does the yellow pill from the trigestrel pill work?

The yellow pill in the Trigestrel contraceptive pack is typically a placebo or inactive pill taken during the last week of the cycle. It does not contain hormones and is included to maintain a consistent daily pill-taking routine. This allows for a withdrawal bleed resembling a menstrual period while preventing ovulation and regulating the menstrual cycle during the active weeks when hormone-containing pills are taken.