Changes in Menstrual Cycle in Ladies Only Posted January 23, 2015 BC holds hormones steady and doesn't allow for the hormonal fluctuations that prompt ovulation. When you stop taking the pills, the drop in hormones triggers menstruation like it does for those not on bc. However, when you adjust your eating, your body's own hormones can fluctuate, and anything considered a drop will cause bleeding. Ah, ok, I get it now. Thanks!