We applied semiparametric spatial Poisson models to analyse fertility decisions at individual level in Malawi. We used the 2000 Malawi Demographic and Health Survey (MDHS) to investigate determinants of fertility, in the model that allowed for nonlinear, fixed and spatial risk factors. Inference was based on the Bayesian approach. The unstructured spatial effects were modelled using the exchangeable prior, while for the structured spatial effects we used the intrinsic conditional autoregressive models. Nonlinear effects were modelled using P-splines. Results showed non-linear declining trends of fertility with year of marriage and increasing trends with age at marriage. We also observed significant unstructured effects, however, no significant spatial autocorrelated effects were displayed. Overall, total spatial effects were significantly different at district level.