Emergency Contraception May Not Prevent Implantation of Fertilized Eggs

An article in the New York Times yesterday presented the information that emergency contraceptive pills (Plan B) likely do not prevent implantation of a fertilized egg, as previously thought. The article examined over a decade’s worth of science that studied the pills and how they work and reports that a consensus is emerging that the medication’s two main mechanisms for preventing pregnancy after intercourse are delaying ovulation and thickening cervical mucous to inhibit the movement of sperm in the genital tract. This is in direct contradiction to package inserts and leading medical websites which include preventing implantation as one of the ways the pills can prevent pregnancy.

But an examination by the New York Times has found that the federally approved labels and medical Web sites do not reflect what the science shows. Studies have not established that emergency contraceptive pills prevent fertilized eggs from implanting in the womb, leading scientists say. Rather, the pills delay ovulation, the release of eggs from ovaries, which occurs before eggs are fertilized, and some pills also thicken cervical mucus so sperm have trouble swimming.

The notion that morning-after pills prevent eggs from implanting stems from the Food and Drug Administration’s decision during the drug-approval process to mention that possibility on the label despite lack of scientific proof, scientists say, and objections by the manufacturer of Plan B, the pill on the market the longest. Leading scientists say studies since then provide strong evidence that Plan B does not prevent implantation and no proof that a newer type of pill, Ella, does. Some abortion opponents said they remain unconvinced.

This new information about how emergency contraception functions doesn’t fundamentally change anything about how the drug is administered or how effective it is. It just means we can now cross one possible outcome of using it off the list: namely, that it changes the uterine lining to prevent implantation of a fertilized egg. One study the Times reported on explicitly demonstrated that the pill’s effectiveness before ovulation is far greater than if taken after:

Later, in 2007, 2009 and 2010, researchers in Australia and Chile gave Plan B to women after determining with hormone tests which women had ovulated and which had not.

None who took the drug before ovulation became pregnant, underscoring how Plan B delays ovulation. Women who had ovulated became pregnant at the same rate as if they had taken no drug at all. In those cases, there were no difficulties with implantation, said one of the researchers, Gabriela Noé, at the Instituto Chileno de Medicina Reproductiva in Santiago. Dr. Blithe of the N.I.H., said, “No one can say that it works to inhibit implantation based on these data.”

If this new information doesn’t change how women take emergency contraceptives orĀ  how well they work at preventing pregnancy, why is this news important? Well, because there’s been a moral argument against emergency contraception offered by those who feel that preventing implantation is tantamount to abortion. Emergency contraception has been caught in the net of fetal personhood debates as a medication that could be restricted if fertilized eggs are ever given so-called personhood rights. And there have been reports of doctors or pharmacists activating legal “conscience clauses” and refusing to dispense emergency contraception, even in the case of rape, because they have a moral objection to the possibility that it could prevent a fertilized egg from implanting.

Theoretically, if a scientific consensus arises that says the pills do NOT prevent implantation, emergency contraception should be removed from anti-choice lists of concerns. Whether or not that will happen remains to be seen. For now, we know that scientific review is on-going and emergency contraception remains as safe and effective as ever when taken as directed.

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Article Posted 4 years Ago

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