OBJECTIVES: To describe the prevalence, management and outcome of spontaneous twin anemia polycythemia sequence (TAPS) diagnosed in the prenatal period. METHOD: Retrospective analysis of 142 consecutive monochorionic twin pregnancies not diagnosed with twin to twin transfusion syndrome. TAPS cases were identified based on the presence of discordant middle cerebral artery peak systolic velocity (MCA-PSV) measurements and signs suggestive of a chronic intertwin transfusion imbalance: either an elevated reticulocyte count in the anemic twin or the presence of few small unidirectional anastomoses during fetoscopy or at postnatal placental examination. RESULTS: Three cases were identified, giving an estimated prevalence of 2%. Prenatal interventions were tailored to the characteristics of each case and consisted of intrauterine transfusion and interruption of the shared circulation by cord coagulation or laser separation. CONCLUSION: In monochorionic twin pregnancies, TAPS is an uncommon prenatal finding. Nonetheless, its incidence seems high enough to recommend screening for this disease by MCA-PSV measurements.