The vaginal ring is a method of birth control that contains artificial forms of the hormones that are normally produced in the ovaries of women: oestrogen and progestin. These hormones prevent the ovary from releasing an egg during the menstrual cycle. The progestin hormone also helps to prevent sperm from entering the uterus by thickening the mucus in the cervix. It is a flexible ring about five inches in diameter that women can place inside the vagina by themselves. It is a monthly contraceptive: it must remain in the vagina for three weeks and then remove it and rest for a week. It is important to keep in mind that this method can produce side effects such as nausea, vaginitis or bleeding between periods.