Africa has higher rates of fertility than anywhere else, which limits the ability of a demographic transition to positively influence economic and socio-economic prospects on the continent. This research delves into the ineffective implementation of fertility limiting preferences. We develop a theoretical model formalising the various determinants of a woman’s reproductive health behaviour during her reproductive years, focussing on choices related to effective contraception. The model incorporates the cyclicality and volatility of fecundity, paying particular attention to the stochastic nature of the reproduction process, as well as potential costs (such as lost wages and direct costs of purchase) and benefits (such as the ability to invest in her education and/or career) of being able to control or at least mitigate the volatility in the reproductive process. The model generates heterogeneity in the choice of contraceptive quality depending on both biological and economic factors. The nonparametic control function model, based on Malawian data, supports the notion that both biological and economic factors affect contraception decisions. The results suggest that fertility limiting preferences are being met, at least partially, in Malawi, and that the demographic transition is gaining traction.