Professionals compete and cooperate over how states should govern their population. Declining fertility rates in advanced economies have led to debates about how to enable those of reproductive age to have more children and to have them earlier. This springs from political and socio-economic concerns about fulfilling desired fertility rates, maintaining high levels of human capital, and supporting fiscal and pension systems. This article investigates professionals addressing declining fertility through assisted reproductive technologies (ART), including doctors, demographers and economists. These professional groups have their own bodies of knowledge on how they view fertility, fecundity and the role of women in social reproduction. They can also cooperate to create ‘issue linkages’ on ART across their professional ecologies. The article discusses how professionals apply their bodies of knowledge to the political economy of fertility. Professional bodies of knowledge directly inform how women and men are treated on fertility issues and the policy options available.