This project aims to establish if and how infertility affects the risk of cardiovascular disease in both men and women. By using genetic markers as instrumental variables, we will establish any causal relationship between cardiovascular risk factors (smoking, body-mass index, blood pressure, lipids, glucose and insulin) and infertility in both sexes. If we observe a clear link between classical cardiovascular risk factors and infertility, this highlights a role of a pre-existing underlying risk of cardiovascular disease in infertility. We will also examine whether children of infertile couples have a poorer cardiometabolic health compared to children of fertile couples, to understand whether cardiometabolic factors might contribute to the familiar aggregation of infertility. To better answer this question, we will also identify any genetic markers which affect infertility in men and women, to use these as instrumental variables in causal inference methods.