Effect of birth weight on the formation of ECFC colonies. CB-MNCs from 25 LBW preterm or 25 control neonates were seeded onto gelatin-coated wells and observed every 2 days as described in “Methods.” (A) Time-dependent appearance of ECFC colonies after MNC plating of 25 LBW preterm neonates and 25 controls (left), and according to birth weight (right). Data are mean ± SEM of 25 independent experiments. **P < .01. ***P < .001. (B) Numbers of ECFC colonies formed by CB-MNCs according to birth weight (left) or to gestational age (right). (Inset) Spearman correlation coefficient for colony formation in response to birth weight or to gestational age. Filled symbols indicate LBW preterm neonates with IUGR: (★), 680 g, 29 weeks; (●), 930 g, 31 weeks; (▾), 940 g, 32 weeks; (▴), 1700 g, 35 weeks; and (■), 1850 g, 36 weeks. Data represent mean of 25 independent experiments. NS indicates not significant.