Are you experiencing light or moderate bleeding before your period? Commonly known as spotting or breakthrough bleeding, intermenstrual bleeding affects many women across the country. While there are numerous possible causes, the following three are some of the most common. Contraception One of the most common causes of spotting is using contraception. Contraceptive pills, implants, injections, patches and all other hormonal forms of birth control can all cause bleeding in the lead-up to your period.