“Were you lying then, or are you lying now?” So asks an outraged defense lawyer in the great courtroom drama Witness for the Prosecution, when his star murder witness reverses her testimony. In light of recent events, some may want to ask the same question of the American College of Obstetricians and Gynecologists (ACOG).

ACOG presents itself as a defender of scientific truth about human reproduction. “ACOG firmly believes that science must be at the core of public health policies and medical decision-making that affect the health and life of women,” the organization has declared. It is purportedly in this spirit that ACOG has offered, in friend-of-the-court briefs, to show the Supreme Court how to resolve pending lawsuits that say the Administration’s contraceptive mandate infringes on religious freedom. Yet a look at ACOG’s factual claims before the court, and the claims it is making in other forums about the very same facts, raises troubling questions.

ACOG’s Friend-of-the-Court Briefs

First, the court cases. Hobby Lobby and other companies owned and operated by devout Christians have urged the Court to exempt them from covering four specific birth control methods—those that attack the newly conceived unborn child, by preventing his or her implantation in the mother’s womb. The cited methods are the “emergency contraception” drugs Plan B and Ella, as well as two types of IUD (hormonal and copper). The owners do not object to contraception; that is, to drugs that prevent ovulation or fertilization. But they do object to abortion, and believe that any attack on a new human life after fertilization constitutes abortion. Forcing them to facilitate such attacks would gravely burden their freedom to practice their faith.

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In an October 2013 brief urging the Court to take up the Hobby Lobby case, ACOG and other “pro-choice” medical groups offered to help Hobby Lobby get its facts straight. They did not challenge “the sincerity of the owner’s belief that the use of such contraceptives would be wrong.” However, they said, Hobby Lobby’s claim about how these drugs and devices work is “a scientific matter” subject to verification. According to ACOG and the other signers:

Respondents’ claim that Plan B and Ella prevent implantation is not supported by current scientific data or by evidence in the record below. To the contrary, scientific research shows that Plan B and Ella both function by inhibiting or postponing ovulation; they do not prevent fertilization or implantation. . . . Equally unsupported is Respondents’ characterization of any of the FDA-approved contraceptives or emergency contraceptives as “abortifacients.”

Once the Supreme Court accepted the Hobby Lobby case, ACOG and other medical groups submitted a brief on the merits of the case, again urging the court to act on the factual claims in their earlier brief.

This seems straightforward. ACOG is saying that Hobby Lobby was simply wrong to think its religious convictions about respect for nascent human life were implicated here. “Scientific research shows” that these methods don’t work after fertilization.

Contradictory Claims and Word Games

But here’s where the problem arises: ACOG and some of these other medical groups have been publicly declaring, at the same time, that “science” shows exactly the opposite to be true. They argue that, because a variety of commonly used birth control methods do attack embryos after fertilization, legislators and voters should defeat efforts to declare legal personhood for human beings from fertilization onward.

ACOG’s current public position is that these initiatives “would make condoms, natural family planning, and spermicides the only legally allowed forms of birth control.” In other words, ACOG says that a ban on killing embryos after fertilization would ban all the contraceptive methods covered by the HHS Mandate.

One month before ACOG filed its Hobby Lobby brief in October, the Washington Post editorialized that “the practical effect of ‘personhood’ measures . . . would easily include banning the most popular forms of contraception. This is because the pill, as well as other forms of birth control, work partly by preventing the implantation of eggs in the uterus wall [sic] after they have been fertilized. Here the Post cited that objective voice of medical science, ACOG, which holds that “some of the most effective and reliable forms of contraception—oral contraceptives, intrauterine devices, and other forms of FDA-approved contraceptives—would be banned” by a law that respects life beginning at fertilization. That is, ACOG holds this to be true except when it is filing briefs saying it is false.

The same doublespeak is found among other medical groups signing the Hobby Lobby brief. For example, the American Society for Reproductive Medicine has a current position statement declaring: “Personhood measures would make illegal some commonly used birth control methods.”

In the case of the copper IUD, one birth control method to which Hobby Lobby objects, even ACOG’s brief was unable to claim that it does not prevent implantation of the new embryo because there is a fairly strong medical consensus that it does just that. Here the brief uses a different tactic, claiming that “the medical and scientific community” sees words like “abortion” and “abortifacient” as applying only after implantation. So this method does kill embryos, but should not be called “abortion.”

That is not a scientific finding but a semantic game. Obviously, what raises the moral problem of abortion for Hobby Lobby and so many others is that it can destroy an embryonic member of the human species; even ACOG’s brief admits that is a relevant consideration regarding the copper IUD. But the medical establishment (and its friends in the pharmaceutical industry) began changing the definition of “conception” in the 1960s, to equate it with implantation—precisely because evidence was emerging that the new method known as the IUD might prevent implantation, and they wanted to continue calling the IUD a “contraceptive” even if that evidence was correct. Thus, “abortion” was defined to cover only the disruption of an already implanted pregnancy.

The new definition was useful for obstetricians, who have no reliable way to detect a pregnancy until after implantation anyway. It has been especially handy for pro-abortion doctors, who like to see pregnancy as primarily a condition of the woman (and to see abortion as freeing her from that condition). But to embryologists, human development begins with fertilization; implantation in the womb is a change in location for the embryo, but it’s only one stage in development among others. To them, the terms “conception” and “fertilization” mean the same thing. And the last time I checked, embryology is a science.

But ACOG’s word game over “conception,” masquerading as scientific fact, is an old story in the abortion debate. The new and appalling development here is the fact that powerful and once-respected medical organizations are simultaneously insisting that certain birth control methods both do and do not have post-fertilization effects—based solely on which factual claim will thwart pro-lifers on any given day, or in any given context.

This raises an obvious question: Which of ACOG’s contradictory claims is true?

The Scientific Evidence

Let’s set aside, for the moment, the case of the copper IUD, where the medical consensus seems clear—it does interfere with implantation. Regarding the other three methods, what can science tell us?

There are conflicting studies and rival claims, but none of the drugs and devices cited by Hobby Lobby are proved to work only before fertilization. Because there is no reliable and direct test for whether fertilization has occurred in a woman’s body, one must make inferences from indirect evidence. But Ella, for example, is known to be a close analogue to the “abortion pill” RU-486, and in animal tests (including tests on nonhuman primates) it can both prevent implantation and disrupt pregnancy after implantation.

The evidence is less certain about the “emergency contraceptive” Plan B, but recent studies show that an anti-implantation effect cannot be dismissed. Some evidence suggests that even when taken before ovulation, the drug may interfere not with the release of an egg by a woman’s body but with the burst ovarian follicle’s task of preparing the uterus to receive the new embryo. ACOG’s brief claims that Plan B’s apparent lack of effectiveness when given after ovulation proves that it has no abortifacient (anti-implantation) effect, but that is not necessarily true.

So, concerns on the part of Hobby Lobby and others about being forced to facilitate the loss of newly conceived human life seem to be well-founded. It is ACOG’s brief that ignores the facts.

Does this mean that ACOG’s opposite claim—that a law recognizing the new human embryo as a person would make birth control illegal—is valid? Not necessarily. Some commonly used birth control drugs, like the ordinary oral contraceptive, are widely thought to act by preventing fertilization all or almost all the time; the non-Catholic family that owns Hobby Lobby did not even raise an objection to them. In the case of a drug or device that sometimes prevents fertilization, but sometimes may interrupt human development after fertilization, the former (legally valid) use would surely be raised in any legal argument—especially in a legal system where contraception is constitutionally protected. And no one claims to be able to prove in an individual instance how such a method has actually functioned.

Downplaying Health Risks

Unfortunately, government has shown a marked tendency to keep various birth control methods on the market despite the risk they may pose to the lives of women, who are certainly persons. For example, contraceptive drugs containing drospirenone, such as Yaz and Yasmin, have been associated for years with a substantially increased risk of blood clots, which can lead to pulmonary embolism and death. Over ten thousand patients have filed lawsuits against the manufacturer. But so far, all the FDA has done is consider a new warning label.

The government and some self-declared expert organizations have a long record of hyping the health benefits of contraceptives and downplaying their risks. The Obama administration’s own regulation says its contraceptive mandate promotes public health by, among other things, assisting in the “prevention of certain cancers.” The administration failed to mention that while some contraceptive drugs may be associated with a decreased risk of endometrial and ovarian cancer, they seem to pose an increased risk of breast and cervical cancer and some liver tumors. It is valid to ask whether that same casual attitude toward these drugs’ risks to women would also play a role in the law’s assessment of risks to the unborn child.

But that doesn’t mean religious believers should be forced by law to have that same cavalier attitude regarding the lives of either women or their unborn children. It is their moral concern about the sanctity of life, not the government’s, that is relevant to the Hobby Lobby case, and that concern is well grounded.

So ACOG seems to have achieved something rather special. It has declared a medical claim to be both true and false at the same time, depending on the political context; and it may have managed to exaggerate or misstate that claim’s relevance to the issue at hand in both contexts.

Politicizing Science

This is not the first time that ACOG has politicized medical science, with devastating impact on public policy. In 1996, for example, it issued what purported to be an analysis of the “intact D&X” or partial-birth abortion procedure by a panel of medical experts. Originally, the ACOG statement said that its select panel “could identify no circumstances under which [the partial-birth] procedure . . . would be the only option to save the life or preserve the health of the woman.” But this text was sent to an aide in President Clinton’s domestic policy office, who wrote back that the statement would spell “disaster” for political efforts by ACOG and the White House to defeat a ban on the procedure. So policy staff with no medical background drafted a different punch line for the ACOG statement, saying that this procedure nonetheless “may be the best or most appropriate procedure in a particular circumstance to save the life or preserve the health of a woman.”

ACOG inserted that political spin into its supposedly expert statement—and that one sentence was quoted over and over by federal judges to invalidate state bans on partial-birth abortion, by the Supreme Court when it knocked down Nebraska’s ban in 2000, and by dissenting justices when the Court finally upheld a federal ban in 2007.

We all may have moments when we are tempted to ignore inconvenient facts, to be selective in marshalling evidence, or even to say different things at different times to help us prevail in some dispute. What’s disturbing is that a group presenting itself as an authoritative guide to medical science may see these not as temptations but as standard practice.