NuvaRing birth control is a combination hormonal contraceptive. It is manufactured by Organon USA. NuvaRing is a polyethylene vinyl acetate ring around 2 inches in diameter. It is worn in the vagina for three weeks and then removed for one week. The ring contains a combination of the hormones estrogen and progestin. NuvaRing birth control slowly releases the hormones into the bloodstream. The progestin is absorbed and prevents the ovary from releasing an egg. In addition, the uterine lining becomes thinner and the cervical mucous becomes thicker. NuvaRing is considered a third-generation contraceptive.

Oral contraceptives are usually made up of a mix of synthetic female hormones. First-generation birth control pills, first introduced in the 1960's, had high levels of the hormones estrogen and the progestogens lynestrenol or norethisterone. The early contraceptive pills caused a fairly high number of blood clots resulting in blockages in the legs, heart, and brain. These blockages can then lead to heart attacks and strokes.

Second generation birth control pills were formulated to decrease the risk of blood clots. They contained lower amounts of estrogen and a different progestogen called levonorgestrel. The downside to these second generation contraceptive pills was that they caused side effects such as acne, hirsutism (increased hair growth), weight gain, and higher cholesterol levels. Second and third generation oral contraceptives differ in their progestin component.

Third generation birth control pills such as NuvaRing were developed in the 1980's to contain the progestogen hormones desogestrel or gestodene. The goal was to help reduce adverse effects such as hirsutism and acne. It is estimated that 7.5 million women filled prescriptions for third generation oral contraceptives in the United States in 2006. Studies have found that women using third-generation oral contraceptives have an increased risk of venous thromboembolism (blood clot) compared to users of second-generation contraceptives containing levonorgestrel.

Some researchers are questioning whether third-generation contraceptives such as NuvaRing are more safe and effective than second-generation contraceptives given the increased risk of blood clots. The focus has been on desogestrel, the synthetic form of the hormone progestin. Desogestrel appears to cause resistance to one of the anti-coagulant proteins (Protein C). When coagulation is inhibited it makes it easier for blood clots to form which increases the risk of venous thrombosis.