Objective: To investigate the prognostic factors for primitive fetal hydrothorax (PFHT) and propose a clinical strategy based on systematic literature review. Methods: We reviewed 64 articles describing 204 cases of PFHT. For each case we focused on 11 criteria. We investigated prognostic factors in the 89 cases where no in utero treatment was undertaken. We also studied the impact of different in utero treatments on the evolution of PFHT. Results: We have found 4 factors correlated with the course of PFHT: the presence of hydrops, gestational age at time of birth, the unilateral or bilateral nature of the effusion, and the occurrence of spontaneous resolution. With multivariate analysis, only hydrops remained determinant as a prognostic factor. Conclusions: Studies such as ours, reviewing case reports or series, are subject to the biases of literature underreporting of therapeutic failures or nonintervention. However (with the best available data) we propose a clinical approach to PFHT discovered in utero.