Residual blood volume in the umbilical cord of extremely premature infants

BackgroundThe aim of this study was to investigate residual blood volume in the umbilical cord of extremely premature infants. MethodsTwenty extremely premature infants were held at or below the placenta while the umbilical cord was clamped and cut at approximately 2-3cm from the umbilicus within 30s after birth. The umbilical cord was then clamped near the placenta to obtain a length of approximately 30cm and cut. The residual blood volume in the segment of cord was drained and measured in milliliters. ResultsMean birthweight was 846 172g (range, 587-1180g). The average length of the clamped segment of umbilical cord was 29.8 +/- 1.5cm (range, 27-32cm). Total residual blood volume and residual blood volume per cm were 15.5 +/- 6.7mL (range, 6-25mL) and 0.5 +/- 0.2mL/cm (range, 0.2-0.8mL/cm), respectively. The residual cord blood volume per kilogram of infant weight per 30cm was 17.7 +/- 5.5mL/kg/30cm (range, 8.9-29.0mL/kg/30cm). ConclusionInfants could receive approximately 18mL/kg of whole blood by one-time milking of 30cm umbilical cord. With an average hematocrit of 40%, this volume is equivalent to approximately 13mL of packed red blood cells (hematocrit 55%).