Here’s what combined birth control pills and birth control vaginal rings do: They stop ovulation. They thicken cervical mucus. They thin the uterine lining. That’s how they prevent pregnancy. More importantly, they do it by making your hormones stable. They work even better if you skip the placebo/bleeding/week off week. No periods, no PMD, PMDD, less anemia because less blood loss. They also help with: acne, heavy periods, pain from periods, anemia, irregular cycles, PCOS symptoms, endometriosi