Plan B, the "morning-after" contraceptive recently approved for over-the-counter use, is not as effective as a drug company claims, and there is no evidence that the pill's widespread use will reduce the rate of abortions or unwanted pregnancies, argues a Utah doctor who sat on the Food and Drug Administration's advisory panel.

On top of that, Plan B can act as an "abortifacient" — sometimes not preventing fertilization but preventing implantation instead — contends Dr. Joseph Stanford, associate professor of family and preventative medicine at the University of Utah School of Medicine.

This biological nuance is important to people who believe that life begins at fertilization, when the sperm enters the egg, versus others who believe it begins at implantation, when the embryo is implanted in the endometrium.

Stanford hopes that doctors will alert patients that the pill may technically cause an abortion. It's the kind of informed consent only "marginally" addressed in the pill's package insert, he says. "It's the way that it's phrased, to minimize the issue," he adds, referring to the insert phrase "when a fertilized egg implants." At time of implantation, he argues, "the embryo is over 100 cells."

At a medical lecture earlier this week, several doctors in the audience noted that even religious women may be more concerned about preventing an unwanted pregnancy than they are about terminology or how the pill works in their bodies.

One doctor said that when he tells his patients that IUDs may work in a "post-fertilization" manner, "zero patients flinch and say 'I don't want this.' Zero." Religiosity, said another, "may take a back seat" to the desire not to be pregnant, even in Utah.

Another doctor expressed concern about what he called a more important moral issue: that the drug company marketing Plan B may be overstating its effectiveness and therefore "taking advantage of women in a vulnerable situation." Ads for Plan B boast that "seven out of eight women won't get pregnant."

Plan B, approved a month ago for over-the-counter use, can prevent pregnancy if used within 72 hours after intercourse. It is more effective the sooner it is taken, which was the rationale used by the FDA for approving its nonprescription use.

According to its manufacturer, the drug is effective in 89 percent of cases. But Stanford argues that studies done by him and other researchers show a lower effectiveness rate. "We did more a precise meta-analysis that shows it's effective only 72 percent of the time, and even that number is optimistic," he says.

The overestimate, he says, results in part because early studies did not take into account normal variations in the timing of ovulation during women's menstrual cycles.

The more effective the drug is — that is, the more days it works after intercourse — the more likely it works by preventing implantation rather than fertilization, he says.

Some medical dictionaries define conception as the moment when the sperm enters the egg; others define it as "the implantation of the blastocyst in the endometrium." That second usage is "a deliberate redefinition," argues Stanford, who has been a vocal advocate for the belief that even regular oral contraceptives also sometimes act as abortifacients.

According to studies he has conducted, he says, religious women are more likely to be concerned that a contraceptive method may have a post-fertilization effect. Age, race, income, education and plans for future pregnancy were not as important as religion, he says.

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Although proponents of emergency contraceptives say that the pills will cut down on the number of abortions and unwanted pregnancies, Stanford says that studies in Europe, China and the United States prove otherwise.

"In all cases, they found there was no effect on abortion rates and unintended pregnancy rates," he says. It's a "naive view of human nature" to think that people won't indulge in "riskier" behavior if they think they can rely on a morning-after pill, he says.

Stanford served on the FDA's advisory council that examined whether Plan B should be given over-the-counter status. Federal hearings in 2003 were "a mix of science, theater and politics," he says, resulting in a 23 to 4 vote to approve the drug for OTC use. Stanford was one of the four who voted "no."