The consumer advocacy group Public Citizen has petitioned the U.S. government to pull the birth-control patch off the market, saying that it is far riskier than the pill.

Warnings about the Ortho-Evra weekly patch have escalated since a 2005 investigation found patch users face higher rates of life-threatening blood clots than women who take birth-control pills. Demand has dropped from about 9.9 million prescriptions filled in 2004 to 2.7 million filled in 2007.

Some studies suggest patch users have twice the risk of clots in the legs and lungs as women who use the pill, because patients on the patch absorb up to 60 percent more estrogen.