The study contributes in analytical description of spatial diffusion of fertility, in particular, influenced by labour movements of people between places of residence and work. It is assumed that the labour market has externality on the marriage market due to commuting, which, in turn, affects fertility. A model of spatial diffusion of fertility is based on assumption of global and local spillover effects. The global spillover effect, as shifts in fertility norms, is motivated by increasing variance of social interactions of an individual, when places of work and residence are different. One local spillover effect is in response to flows of earnings across space. Another mechanism is related to expected changes in probabilities to find a partner affected by differences in day and night population. The analytical model, in which the effects on fertility of the cited spillovers are decomposed, is constructed in the paper on the base of a model of the demand for children, spatial stock-flow model of a market, and a matching model with a sex imbalance or spatial mismatch as the probability of matching. Three sex imbalances, namely of night-, day-time population and an adjusted to sex imbalance of commuters to residents are empirically tested. Empirical evidence on municipal Swedish data for the period 1994–2008 does not provide any strong evidence of spatial diffusion of fertility. However, there are externalities of labour mobility on fertility due to changes of gender structure of population.