NuvaRing is a flexible ring that is inserted into the vagina on a monthly basis to provide contraception. The ring contains two active ingredients, ethinylestradiol and etonogestrel. The hormones are released into the vagina from the ring, from where they are absorbed into the bloodstream. The hormones are similar to the hormones used in contraceptive pills and work in the same way. Hormonal contraceptives like NuvaRing work by over-riding the normal menstrual cycle.
The hormones also increase the thickness of the natural mucus at the neck of the womb, which makes it more difficult for sperm to cross from the vagina into the womb and reach an egg. They also change the quality of the womb lining, making it less likely that a fertislised egg can implant there.