The vaginal ring is a flexible plastic ring that is inserted in the vagina for three weeks out of four. It contains hormones (estrogen and progestogen) which are similar to the hormones naturally produced.

A constant dose of hormones is released from the ring into the bloodstream through the vaginal wall which stops the ovaries from releasing an egg each month (ovulation).  They also thicken the mucus in the cervix preventing sperm reaching the egg and thin the lining of the uterus so it is less likely to accept a fertilised egg.