A Supreme Court decision requiring states to redefine marriage would undermine the institution of marriage generally, as a number of scholars have shown. That’s particularly bad news for women and children from socioeconomically disadvantaged communities, according to an amicus brief filed in the pending marriage case by scholars of women’s and children’s welfare.

As Traditionally Understood, Marriage Is Especially Beneficial to Underprivileged Women and Children

As these scholars explain, like all social institutions, marriage guides behavior. And historically, it developed to channel men and women into stable, permanent relationships, where they would limit sexual activity to each other and together raise their offspring. Marriage was thus like a footstool sitting on the three legs of sex, procreation, and childrearing—with all of those legs being implicit in the traditional man–woman definition of marriage.

While man–woman marriage benefits all, it is especially beneficial to women and children in underprivileged situations. Women experience substantial financial gains from marriage, and children are much less likely to be in an economically distressed household—with all its challenges for the child—when their parents are married. Thus, as family law scholar Amy Wax notes, social science has found that “marriage is effective in lifting many mothers and children out of poverty.”

Redefining Marriage Would Erode Its Child-Centered Public Meaning

But just as disadvantaged women and children are the most helped by a vibrant marriage institution, they are the most hurt when the institution is weakened—as it would be if the Supreme Court requires states to accommodate same-sex couples by redefining marriage in genderless terms.

Such a redefinition would forever change the public meaning of the institution in at least three ways. First, by removing gender diversity, it would mandate a vision of marriage in which the presence or participation of a man or a woman is no longer considered important in forming a family and raising children. In other words, mothers and fathers would be optional, interchangeable pieces of family life. Try telling that to a child.

Second, a redefinition would undermine marriage’s prioritization of biological kinship: Now the government would be forced to say that a biological connection is, at least for one of the parents, irrelevant. That, too, would discourage fathers from marrying the mothers of their children. For that reason and because in underprivileged communities grandparents increasingly are raising grandchildren (because of their biological connections to the children), severing this biological link could be disastrous for these kids.

Third, removing the man–woman definition would eviscerate the sex-procreation-childbearing nexus that the marriage institution now provides. The result would be a permanent promotion of the wants of the adult as the defining foundation of marriage, with children taking a back seat. As these scholars warn, a redefinition would forever “emphasize that marriage is designed for the adults who enter into it, rather than the children created from it,” thereby reducing marriage to a “mere governmental capstone of a loving relationship.”

The Practical Harm from a Redefinition Would Fall Disproportionately on Underprivileged Women and Their Children

History, moreover, has demonstrated that the socioeconomically disadvantaged are more vulnerable to changes in the institution of marriage and that fatherhood is more sensitive to these alterations than motherhood. Accordingly, these scholars predict that, over time, a redefinition-induced erosion of the traditional norms of marriage would lead many socioeconomically disadvantaged men to eschew marriage altogether. The result would be more children born to more single women mired in economically and psychologically stressful situations.

On the other hand, the educated and the comparatively well-to-do—those who less need the reinforcing messages of the institution of marriage—would likely see less of an effect from a redefinition. That is why, as the brief explains, it is important for intellectual and social elites not to fall into the trap of viewing “the consequences of redefining marriage only from [their] own unique perspective[s].” Already there is a great cultural divide over marriage: The rich and the educated marry; the poor and the uneducated increasingly don’t. This chasm would only grow with a redefinition.

For all these reasons, a redefinition would likely produce at least three deleterious practical consequences. First, more women would be raising children as single mothers. Second, more man–woman couples, especially in underprivileged populations, would choose cohabitation over marriage—an arrangement that looks very little like marriage in its benefits to women and children. Third, more man–woman unions would dissolve, leaving women and children worse off.

As Ghandi purportedly observed, “The true measure of any society can be found in how it treats its most vulnerable members.” Redefinition of marriage undermines the institution of marriage, and over time that will have negative long-term implications for low-income mothers and their children. The Supreme Court should keep these women and children in mind as it decides whether to “constitutionalize” the definition of marriage or instead to leave that choice to democratic processes.