It wasn’t always this way. Before Roe v. Wade, those on both sides of the issue typically framed their arguments in constitutional terms, anticipating a showdown in the courts. And in the immediate aftermath of the decision, 46 years ago today, most still viewed abortion as a constitutional fight. Abortion foes pushed for an amendment banning the procedure and restoring what they saw as a fundamental right to life; abortion-rights supporters felt secure in the court’s conclusion that the 14th Amendment’s right to privacy encompassed a right to choose.

The introduction of scientific claims to the debate came slowly at first. In the 1970s, anti-abortion activists wanted a way to keep abortion rates down while the campaign for constitutional change raged on. So they turned to contested science to argue for laws dictating how and when doctors performed abortions. Some insisted that fetal viability came earlier than the 24- to 28-week time frame set in Roe. Others claimed that abortion caused “severe emotional disturbances,” “sterility and miscarriage, and prematurity in subsequent pregnancies.” In the decade that followed Roe, dozens of laws restricting abortion were passed each year.

By the 1980s, abortion foes had conceded that a constitutional amendment would not pass in the foreseeable future. Even with allies controlling Congress and the White House, there simply weren’t enough votes for an amendment banning all abortions outright, and absolutists saw any other form of constitutional change as cowardly and counterproductive.

And so anti-abortion groups decided that their best bet would be passing yet more restrictions on when, where and how doctors performed abortions and persuading the court to uphold them. With that, arguments over what science had to say about the procedure took on even more importance. The 1980s saw the advent of arguments that stressed fetal pain — an issue on which there is very little consensus — and a continuing push to redefine fetal viability.

While accusing opponents of peddling sham science, abortion-rights supporters insisted that the legality of the procedure should turn on its benefits for women seeking a more equal role in society. In 1992, in Planned Parenthood v. Casey, the court agreed, declining an invitation to overturn Roe partly because “the ability of women to participate equally in the economic and social life of the nation has been facilitated by their ability to control their reproductive lives.”