The Supreme Court of the United States (or SCOTUS for short) handed down a decision today in the case of Burwell v. Hobby Lobby Stores which, essentially, rewrites rules on corporate healthcare compliance if corporations have religious exemption claims.

There's a lot that people can say about their opinion about the decision, and if you want to in the comments then feel free. But I want to focus on the primary scientific claim of the case in order to determine if bad science led to this decision.

The primary scientific claim contained in the decision

Nonexempt employers are generally required to provide coverage for the 20 contraceptive methods approved by the Food and Drug Administration, including the 4 that may have the effect of preventing an already fertilized egg from developing any further by inhibiting its attachment to the uterus.

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Although this is stated somewhat weakly, this sounds like a testable hypothesis: four contraceptive methods inhibit implantation. What does science say about this hypothesis?

What are these four contraceptive methods?

The 20 FDA-approved contraceptive methods are the 20 mentioned in this pdf and discussed at this website. The FDA mentions that both of its listed forms of emergency contraception (one group consisting of Plan B, Plan B One Step, and Next Choice, and another group consisting of Ella) "may also work … by preventing attachment (implantation) to the womb (uterus)" and "may also work by changing the lining of the womb (uterus) that may prevent attachment (implantation)." The FDA mentions that copper IUDs "may prevent the egg from attaching (implanting) in the womb (uterus)." and that an IUD with progestin "also thins the lining of your uterus.", which could prevent a fertilized egg from implanting on a uterus. So the four methods are two forms of emergency contraception and two forms of intrauterine devices.

Do emergency contraceptive methods inhibit implantation?

The FDA says yes, although science does not support this. The FDA's label for Plan B One Step mentions "it may inhibit implantation (by altering the endometrium", and a recent op-ed in the New England Journal of Medicine by Wood et al. mentions, for that same medication, that "prevention of implantation cannot be ruled out". But, as this New York Times article from 2012 discusses, there is no positive evidence that the medically-active ingredients in Plan B or Ella inhibit implantation in humans at the levels used in those medicines. For instance, work published in 2002 cited earlier work on RU-486, which does inhibit implantation, and which uses a similar ingredient as what Ella contains. But the amount of active ingredient is much larger in RU-486 than in Ella (30x larger), making it unlikely that Ella can inhibit implantation. In short, RU-486 has been scientifically proven to act to inhibit implantation and disrupt implantation, whereas Ella has not been scientifically proven to do either of those.

Do intrauterine devices inhibit implantation?

Yes. Research on humans and non-humans both support the contention that IUDs, both copper-containing and progestin-containing, can inhibit implantation. This is not the primary manner in which IUDs prevent pregnancy (they have both prefertilization and postfertilization effects), but IUDs do appear to inhibit implantation.

Did the SCOTUS ignore science today?

Yes and no. While there is no scientific evidence that FDA-approved forms of emergency contraception (three forms of Plan B and Ella) inhibit implantation, there is scientific evidence that IUDs (both copper- and progestin-containing) do inhibit implantation. If Hobby Lobby Stores are interested in preventing their female employers from getting insurance coverage for usage of FDA-approved contraceptive methods that inhibit implantation, they can do so for IUDS but not for emergency contraception.

Did the original claim ignore science or law more?

Interestingly, the original U.S. District Court claim by Hobby Lobby Stores went a few steps further than what the SCOTUS decided on today. It made the scientific claims that Plan B and Ella can both "prevent the implantation of a human embryo in the wall of the uterus" (this is wrong, for both) and that "Plan B, Ella, and certain IUDs can cause the death of the embryo" (which is wrong for Plan B and Ella).

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It also claimed that "the use of artificial means to prevent the implantation of a human embryo in the wall of the uterus" and "the use of artificial means to cause the death of a human embryo" both "constitute an 'abortion' as that term is used in federal law". But, for the first case, that's just not true. To quote directly from the SCOTUS opinion handed out today:

The owners of the companies involved in these cases and others who believe that life begins at conception regard these four methods as causing abortions, but federal regulations, which define pregnancy as beginning at implantation, see, e.g., 62 Fed. Reg. 8611 (1997); 45 CFR §46.202(f) (2013), do not so classify them.

So the SCOTUS decided today for a corporation which began their case on scientifically and legally wrong premises. So if you want to bring a case to the SCOTUS, don't be afraid of having some basic facts about science or law wrong.

Lead image of human uterine tissue from The Human Protein Atlas.