Forty-nine years ago this week, the nine men on the Supreme Court heard arguments that would profoundly affect women's access to birth control. By 21st-century standards, the oral arguments in the 1965 case Griswold vs. Connecticut suggest that most of the justices were either uninformed about contraceptive methods or uncomfortable discussing them. When the court returns to the subject of birth control this week, it is critical that the justices understand the complexity of contraception and its role in women's lives.

The Connecticut law at issue in Griswold criminally punished any person who "uses any drug, medicinal article or instrument for the purpose of preventing conception." The case arose when the medical director and executive director of Planned Parenthood of New Haven, Conn., were convicted of assisting married couples in the unlawful use of birth control.

Oral arguments in Griswold at times verged on incoherence because the justices were embarrassed to discuss methods of contraception. At one point Justice Hugo Black asked the lawyer for the Planned Parenthood directors: "Is the device which you are talking about here described in the record?" He hastened to add: "I won't ask you to describe it." The transcript notes "[laughter]" in the courtroom. No method of contraception was named out loud by the advocates or any of the justices.

The resulting confusion about methods of birth control mattered. It was said that "the devices" were "commonly and notoriously sold in Connecticut drugstores." That led some justices to think that if contraceptives were available despite the law, nothing much was at stake in the case. But only condoms were sold openly. Condoms could escape the ban on devices "for the purpose of preventing conception" by being labeled for another purpose: "the prevention of disease." But that claim could not justify the use of other methods of avoiding pregnancy — methods no one dared mention in the courtroom.

Other methods of contraception that had been developed by then included oral contraceptives, intrauterine coils, diaphragms and cervical caps. All were significantly more effective than condoms in preventing pregnancy, and they had the additional benefit of being under the control of women. Their use, however, required the involvement of physicians.

Many wealthy women in Connecticut had access to these more reliable forms of birth control because they could afford physicians who, in the privacy of their offices, could simply violate the law to serve their patients. When Planned Parenthood sought to open a clinic to make these methods available to lower-income women, state prosecutors invoked the law to shut down the clinic.

Ultimately, the court concluded that the Constitution protects the decision of a married couple to use birth control. Had more of the justices understood the role of different forms of contraception, more might have joined Justice Byron White's additional equality argument that the law effectively denied to "disadvantaged citizens of Connecticut, those without either adequate knowledge or resources to obtain private counseling, access to medical assistance and up-to-date information in respect to proper methods of birth control."

The cases being heard on Tuesday also implicate equality of access to effective methods of family planning. At issue are challenges to the Affordable Care Act's requirement that health insurance policies cover without cost to the patient all methods of birth control for women approved by the Food and Drug Administration. An exemption is being sought by directors of for-profit corporations who hold a religious belief that they would be complicit in sin if the health insurance policies provided to their employees included coverage of birth control methods the bosses consider immoral.

Some of the arguments exhibit the same conflation of methods of contraception that afflicted the Griswold argument a half-century ago. The cabinet manufacturer Conestoga Wood has argued, for example, that because "89% of women who are at risk of unintended pregnancy are already using contraception," denying insurance coverage would be no significant imposition on employees.

This argument fails to account for the fact that some methods of contraception are far more costly and far more effective than others. The hormonal intrauterine device (IUD), for instance, is 45 times more effective than oral contraceptives and 90 times more effective than male condoms in preventing pregnancy, based on typical use. The initial use of implants or IUDs can cost the equivalent of a month's salary for a full-time minimum-wage worker. It is not surprising that one-third of women questioned in a national survey in 2004 said they would change their method of contraception if cost were not a factor.

The Supreme Court has held that any accommodation of religion "must be measured so that it does not override other significant interests," especially those of third parties. The exemption being sought in these cases would do just that. Giving legal force to corporations' objections to covering the use of contraceptives by their employees would deny to thousands of women affordable access to the most effective methods of birth control — a benefit that those women, or the female dependents of employees, earn as part of their employment compensation package.

In these cases, the shifting of a burden to third parties is not merely a matter of economics. More than half of all American women experience an unintended pregnancy, according to a 2008 study, and 40 percent of those pregnancies end in abortion. Improved access to the most reliable methods of contraception would significantly reduce both unintended pregnancy and the need for abortion.

Walter Dellinger is an attorney in Washington. He co-authored, with Dawn Johnsen of the Indiana University Maurer School of Law, a brief for the Guttmacher Institute and professor Sara Rosenbaum of George Washington University supporting contraception coverage. He wrote this article for the Washington Post.