Increasingly, medical and public health recommendations urge all women of reproductive age to minimize health risks to future pregnancies even when pregnancy is not on the horizon. Such advice is predicated on the belief that good pre-pregnancy care will ensure better birth outcomes in the United States. This pre-pregnancy model of health care effectively designates a “zero trimester” in which women are expected, before conception, to anticipate motherhood and prepare their bodies for healthy reproduction. Some health experts believe that pre-pregnancy care will solve many medical and social ills that were not addressed by the prenatal care model that dominated medical thinking in the twentieth century. Others believe it represents yet another attempt to control women’s bodies. In The Zero Trimester, Miranda Waggoner traces the shifting boundaries of reproductive risk and maternal responsibility in America to understand how and why the task of perfecting pregnancies now encompasses the whole of a woman’s reproductive life, from menarche to menopause. Waggoner shows how the zero trimester arose alongside shifts in medical and public health priorities, contentious reproductive politics, and the changing realities of women’s lives in the twenty-first century. The emergence of the zero trimester is not simply about medical and health concerns; it is also, more broadly, about how cultural power and social ideologies can shape population health imperatives and women’s bodily experiences.