The Effect of Timing of Cord Clamping on Neonatal Venous Hematocrit Values and Clinical Outcome at Term: A Randomized, Controlled Trial

In present-day Western practice, the umbilical cord is clamped within 10 to 15 seconds after birth, but this has not proved to be better than waiting 1 to 3 minutes. Some studies show that delayed cord clamping prevents iron deficiency anemia in the first year of life, presumably because approximately 80 mL of blood is “transfused” within a minute after birth and 100 mL after 3 minutes. Other studies, however, suggest that delay in clamping the cord may increase the risk of polycythemia, respiratory symptoms, and hyperbilirubinemia. The present randomized, controlled study examined the effects of clamping the umbilical cord at different intervals after uneventful birth (15 seconds and 1 and 3 minutes) on the venous hematocrit of term newborn infants after 6 hours of life. Hematocrit was estimated in blood taken from the antecubital vein. A total of 291 women were randomized to one of 3 groups with respective average actual clamp times of 13, 60, and 169.5 seconds. Clamp times complied with the randomized goal in at least 90% of all groups. Infant hematocrit values at age 6 hours were 53.5% with early clamping, 57% in the 1-minute group, and 59% in the 3-minute group. Significantly more early-clamp infants had a hematocrit of less than 45% at 6 hours, and significantly more infants in the 3-minute group had a value exceeding 65%, denoting polycythemia. At 24 to 48 hours, a hematocrit of less than 45% was significantly more frequent in the early-clamp group, but rates of high hematocrit did not differ significantly with clamp time. The 3 groups of infants had comparable plasma bilirubin levels 24 to 48 hours after birth. There were no significant group differences in adverse neonatal events, and infants in all groups followed a similar course through the first month of life. There were no substantial differences between mothers in the 3 groups in either the volume of postpartum blood loss or the hematocrit 24 hours after giving birth. Delaying clamping of the umbilical cord for 1 to 3 minutes after birth appears to increase the infant’s hematocrit within a physiological range without harmful effects. The investigators recommend this practice to increase the amount of iron stored by the newborn infant.