Researchers found that between 2006 and 2008, about twice as many women ages 15 to 44 said they had used emergency contraception, compared with women surveyed in 2002 when it was still prescription-only.
The emergency contraceptive Plan B, which contains progestin, has been available in the US since 1999. They cut the risk of pregnancy by stopping the ovaries from releasing an egg.
However, the contraceptive must be taken within 72 hours of having sex - and the sooner, the better. After the first 12 hours the risk of pregnancy increases by 50%.
So in 2006, after years of political controversy, the US approved Plan B for "behind-the-counter" sales to adults - meaning they could get it from a pharmacy without waiting for a prescription. The age restriction was later lowered to 17 in 2009.
In the new study, researchers looked at data from a periodic government survey to see how national rates of emergency-contraception use may be changing.
They found that of more than 6,300 sexually active US women surveyed between 2006 and 2008, nearly 10% said they had ever used emergency contraception.
That compared with a rate of about 4% among women surveyed in 2002, according to findings published online April 1 in Fertility and Sterility.
"It has more than doubled since the last time the data were collected," said Megan L. Kavanaugh, a senior research associate at the Guttmacher Institute in New York who worked on the study.
However, she said in an interview, "its use still seems relatively low, given that it's easy to access. So there's room for improvement."
Kavanaugh and her colleagues think that media attention is likely the reason for the increase in emergency-contraception use in 2006-2008.
The researchers found no change over time in the percentage of women who said their doctors had discussed emergency contraception with them. In both survey periods, 3% of women said they'd received such counselling in the past year.
Lack of change
That lack of change is not especially surprising, according to Kavanaugh, since smaller studies have suggested that health providers are not often bringing the topic up.
The hope, Kavanaugh noted, had been that emergency contraception would lower the national rate of unintended pregnancy. "But so far there's no evidence that this is happening," she said.
Along with the Plan B product One-Step, there is a generic equivalent called Next Choice available without a prescription. Side effects of both products include abdominal pain, fatigue, headache and nausea.
The current study was funded by government and private grants, and the researchers report no financial conflicts of interest. (Reuters Health/ April 2011)