Certain issues have become so noisy and stigmatized that they seem to be all-consuming and invisible at once. Abortion is one of them, and Katie Watson wants to change how Americans talk about it — when, that is, they deign to truly talk about it at all.

Rates of abortion may be on the decline, largely because of long-term contraceptive use, but as Watson points out in “Scarlet A: The Ethics, Law, & Politics of Ordinary Abortion,” the procedure is far from a fringe practice. Nearly one in five American pregnancies ends in abortion (a number that doesn’t include “spontaneous abortions,” the medical term for miscarriages). Nearly one in four American women will have an abortion in her lifetime.

Yet silence perpetuates a belief that abortion is atypical, even when the statistics say otherwise. The conversational void is then filled by advocates on both sides, who emphasize what Watson calls “extraordinary abortion.” Abortion rights activists highlight severe fetal abnormalities and pregnant 12-year-olds; anti-abortion activists highlight pregnancies that are terminated after viability. Such cases are all too real, but fixating on them distorts our understanding of what abortion ordinarily is. Instead of the most common cases, the ones “we discuss most are the ones that occur least,” Watson writes. “There’s something unreal about the American abortion conversation.”

Watson, a bioethicist at Northwestern’s medical school and a senior counsel for the American Civil Liberties Union of Illinois, comes to the debate with her own convictions. Forty-five years ago, with Roe v. Wade, “abortion was correctly identified as a constitutionally protected right, and it must remain legal,” she writes. “That’s not negotiable for me.” What she wants to do is engage directly with the fact that the majority of Americans, even those in favor of abortion’s legality, have deeply ambivalent feelings about abortion itself. “We should be able to acknowledge the complexity of private decision making,” she writes, “without threatening the right of private decision making.”