Abnormal Vaginal Bleeding – WebMD Possible causes of bleeding outside someone’s period. Website Related Posts Irregular Periods – TeensHealth Why irregular periods happen for teens who've started menstruating. YourPeriod.ca – Society of Obstetricians and Gynaecologists This site covers endometriosis, fibroids, bleeding, pain, and a lot of... Bleeding in between periods – NHS Choice A list of possible reasons for irregular vaginal bleeding. Your Period – Sex & U Basic facts on how periods work and what to expect.