Analysis of umbilical cord blood (UCB) transplants shows a correlation between engraftment and total number of infused cells. Thus, it is worth evaluating what maternal and neonatal characteristics and collection techniques may affect the quality of UCB units. A cross-sectional study was performed with 7897 donors sequentially selected in three health care institutions in Brazil from October 2004 to March 2012, in which both quantitative and qualitative approaches were applied. All donors were considered suitable for cord blood collection. The maternal and neonatal characteristics and techniques of collection that influenced the total number of nucleated cells (TNCs; p < 0.001) were type of delivery, newborn weight and sex, and institution of UCB collection. The TNC count was associated with gestational age (p = 0.008), type of delivery (p < 0.001), newborn sex (p < 0.001), newborn weight (p < 0.001), and UCB collection technique (p = 0.003). Center B presented the largest number of nucleated cells in its results (p < 0.001), followed by Center A (p = 0.001). Other characteristics, such as maternal age, were analyzed but were not relevant for the nucleated cell number. This study provides elements for a model that allows an efficient selection of UCB donors, prioritizing candidates who have a better chance to lead to an optimized use of cord blood cells units.