Ovulation biosensors are devices worn on or used with the body, which can help women detect ovulation. The manufacturers of such devices claim that if women know when they ovulate, couples can arrange heterosexual intercourse during this time, and thus increase their chances of conceiving. Within the contemporary UK context, in which becoming pregnant is presented in the popular media, and in medical discourses, as more difficult for women in their thirties and forties, manufacturers' claims are attractive for those trying to conceive. Yet few sociological studies have examined women's practices of ovulation biosensing. Drawing on women's accounts of tracking ovulation, this paper explores how such practices fit into their trajectories of trying to conceive. It examines why ovulation biosensing seemingly becomes helpful, relevant or important during this time. Ovulation biosensors, it argues, alter the landscape of trying to become pregnant by introducing new stages and materialities which seemingly place women closer to conception. Women engage in ovulation biosensing, not only to help them become pregnant, but also as a way to manage the complexities of fertility and the uncertainties of becoming pregnant in contemporary society.