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Study Refutes Claims of Plan B's Effectiveness 11/15/2006 Further studies conclude morning-after pill does not reduce pregnancies. The manufacturer of Plan B, the morning after pill, claims that the drug effectively prevents pregnancy in 89 percent of cases when it is taken within 72 hours after intercourse. The Food and Drug Administration (FDA) used this high efficiency rate as grounds for making Plan B available over the counter.
A meta-analysis1 of the methods used to test the drug's efficiency, however, offers evidence that an 89 percent efficiency rate is optimistic.
Dr. Joseph B. Stanford, associate professor of Family and Preventive Medicine at the University of Utah, conducted the meta-analysis with Rafael T. Mikolajczyk, professor of Public Health Medicine at the University of Beilefeld, Germany. Dr. Stanford was one of four members of the FDA's Advisory Committee who voted against making the drug available over the counter, viewing studies of the drug's effectiveness as necessarily imprecise.
"The 'gold standard' for effectiveness of any method of contraception is considered to be a randomized trial," reads the introduction to the meta-analysis. "This standard is difficult to attain for many methods of contraception, but especially so for emergency contraception, where ethical considerations preclude a placebo controlled trial."
Few women would be cavalier enough to willingly engage in a study requiring sexual intercourse during ovulation in order to test whether a drug would leave them pregnant. Thus, studies of the effectiveness of emergency contraception have not used a placebo, an innocuous substance used in controlled experiments to compare and test the efficacy of a drug.
The lack of a placebo is one of many factors adding to the imprecision of emergency contraception studies. Another source of ambiguity is that such studies rarely take into account the women's specific days of ovulation. Instead, a proxy marker is used for ovulation and the period of time in a woman's cycle when she is fertile.
Dr. W. David Hager, a gynecologist with a subspecialty interest in infectious diseases who practices at the Women's Care Center in Lexington, Kentucky, also served on the FDA Advisory Committee that assessed whether Plan B should be sold over the counter. He agrees that studies determining the effectiveness of the drug should take the day of the woman's cycle into account if the results are to be accurate.
"When you base effectiveness on use throughout the month, without considering the day of the cycle, the results are misleading," said Dr. Hager. "You can see the significant differences in effectiveness based on the method. For example, when looking at Table 5 of [the meta-analysis] the effectiveness varies from 62-88% using Trussell's approach vs. 51-84% using the adjusted approach."
The Trussell approach, in which information about the variable timing of ovulation is disregarded, results in a higher estimate of the drug's efficiency. This approach, most widely used, assumes more days when women are fertile. In reality, the window of fertility is smaller. "Since many young women are using emergency contraception as their method of birth control, rather than using a prescribed birth control method, they will be using it unnecessarily many times," said Dr. Hager.
The adjusted approach, however, includes information about unpredictable ovulation cycles. This added factor serves to make the measurement of emergency contraception's efficiency more precise, reducing conflated estimates.
Dr. Stanford goes beyond the analysis of emergency contraception studies to refute claims that such drugs are vital to reducing the number of abortions and unwanted pregnancies. Studies in countries that have made the morning-after pill accessible to the public without a prescription demonstrate otherwise.
One major study conducted in the United Kingdom found no drop in abortion rates with over-the-counter access to emergency contraception. Another study measuring the impact of ready access to emergency contraception on unintended pregnancies in the U.S. showed no lowering of pregnancy rates.
The American Association of Pro Life Obstetricians and Gynecologists (AAPLOG) released a statement in the wake of these two studies criticizing those who claimed over-the-counter access to emergency contraception would reduce abortion and unintended pregnancy rates by one-half.
Other studies show that emergency contraception actually increases rates of abortion and unintended pregnancy. Teenage pregnancy in Scottish schools among 13- to 15-year-olds rose 10 percent in one year with increased access to the morning-after pill.2 In 2006, the country reported the highest number of abortions since abortion was legalized in 1967.3 In the United Kingdom, abortion rates increased by 6,000 in one year, with the largest leap among girls younger than 16 years old.4
Countries where the morning-after pill is easily accessible have also experienced an increase in sexually transmitted diseases (STDs).5 In the United Kingdom, specific STDs such as gonorrhea increased by 50 percent in only three years after the morning-after pill was distributed without a prescription.6 In a four-year period, the number of cases of chlamydia went up 76 percent, gonorrhea went up 55 percent, syphilis went up 54 percent and genital warts went up 20 percent.7
For more information about false claims surrounding Plan B, click here.
End Notes
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