Making emergency "morning after" contraceptive pills available over the counter hasn't changed contraceptive use or unprotected sex in the U.K.

So say researchers including Cicely Marston, a social science and public health lecturer at London's Imperial College.

Emergency contraception has been available without a prescription in the U.K. since 2001. It's available only by prescription in the U.S. The FDA rejected an application for nonprescription sales of the pills last year.

Hormonal emergency contraception is effective up to five days after unprotected sex. However, it is most effective when used within 72 hours.

Emergency contraception may prevent pregnancy by temporarily blocking eggs from being produced, by stopping fertilization, or by keeping a fertilized egg from becoming implanted in the uterus.

Read Web MD's "Get the Facts About Emergency Contraception."

Read Web MD's "Your Guide to Birth Control."

British Findings

Marston's report is published by BMJ Online First.

The data came from three surveys. About 7,600 women aged 16-49 participated.

The surveys covered contraceptive use, with specific questions about emergency contraception.

The results included:

—No major change in "morning after" pill use when the pills became available over the counter.

—No major changes in use of other contraceptives.

—No major changes in unprotected sex.

Read Web MD's "Common Myths Regarding Sex and Contraception."

The only shift the researchers reported was in the pills' source. More women bought the pills over the counter when that became an option instead of getting them from their doctors, the researchers write.

"Making emergency hormonal contraception available over the counter does not seem to have led to an increase in its use, to an increase in unprotected sex, or to a decrease in the use of more reliable methods of contraception," write Marston and colleagues.

Read Web MD's "Controversy Over Emergency Contraception Drug."

Most Likely Users

Single women and younger women were both three times as likely to use the "morning after" pills. However, more than half of the pills' users — 53% over the three-year period — were older than 25.

Income and education levels were tied to the likelihood of using the pills. There weren't enough nonwhite participants to track use by ethnic group.

The study did not cover women younger than 16. But those women aren't eligible to buy the pills, say the researchers.

By Miranda Hitti, reviewed by Michael W. Smith, MD

SOURCES: Marston, C. BMJ Online First, July 8, 2005. WebMD Medical Reference from Healthwise: "Birth Control: Emergency Contraception." News release, BMJ.