In this work, we explore the NN → πNN reaction within a relativistic model, consistent with two- and three-body unitarity, for the NN and πNN coupled systems. The model is based on effective hadronic interactions. After describing the theoretical input, we compare the predicted NN phase parameters with the phase shift analysis. Our predictions for the NN → πNN spin observables are compared with the available data and with predictions from other models. A clear model dependence is observed. We also examine systematically the dependence of these spin observables on various components of the dynamical input. We identify and isolate some problems related to the present approach and we point out possible directions for future research. / Ph. D.