Background: Most physicians who deliver babies will clamp and cut the umbilical cord immediately upon delivery, but there is no evidence that this practice is optimal. Early cord clamping has been shown to result in a decrease in the neonate's blood volume, and may be associated with hypovolemia and hematopoietic stem cell and iron loss. Conversely, late clamping may result in complications associated with high blood volume (e.g., jaundice, respiratory distress, polycythemia). In the preterm infant, late clamping has been linked to a decreased need for transfusion and decreased intraventricular hemorrhage. This study is a systematic review evaluating the timing of cord clamping in term infants.
The Study: Hutton and Hassan reviewed studies addressing the risks and benefits of early versus late cord clamping, with outcomes related to respiratory status, anemia, polycythemia, jaundice, and specific laboratory values.
Results: Of 37 studies identified, eight randomized trials and seven nonrandomized trials, six of which were rated as high quality, were included. Early clamping was defined in most studies as clamping within the first 10 seconds of birth, and late clamping was defined as occurring with cessation of cord pulsations or at three minutes (two minutes was the minimal cutoff for definition of late clamping in this meta-analysis).
Of 1,912 newborns represented in the 15 studies identified, 1,001 underwent late clamping and 911 underwent early clamping. Hematocrit levels, as measured at hours or days after delivery, were higher with late cord clamping, but the difference was not significant at six months. Similarly, the higher hemoglobin levels found with late cord clamping were no longer significant at two to three months of age.
Blood volume in infants with late clamping was higher in some trials and not significantly different in others, especially with increasing passage of time. Three trials reported higher blood viscosity with late clamping. Mean bilirubin levels were similar regardless of clamping approach. Several trials found higher ferritin levels and iron stores with late clamping. In terms of clinical outcomes, infants with late clamping had lower risk of anemia at 24 to 48 hours and at two to three months of age. When ferritin levels were considered, infants were at lower risk of anemia at six months as well. There were no differences in rates of jaundice. Polycythemia risk within the first few days of life was greater in infants who underwent late cord clamping. Clamping approach had no apparent effect on tachypnea or respiratory distress, or neonatal intensive care unit admission.
Conclusion: Late cord clamping had a beneficial effect on infants' anemia risk and iron stores, an effect that lasted well into the neonatal period. Increased viscosity and polycythemia were associated with late clamping, but did not appear to have any clinical adverse effects. The authors conclude that these findings are particularly important in geographic areas with few resources, where late cord clamping would be the most beneficial approach.
editor's note: A study published in the March 2007 issue of Pediatrics looked at the effects of late cord clamping on cerebral oxygenation in preterm infants.1 The study of infants at a median age of 30.4 weeks found that infants with late cord clamping had similar cerebral blood volumes but higher tissue oxygenation than infants delivered in the conventional manner. Although this study did not evaluate the clinical impact of this finding, it does identify another high-risk group that could benefit from late cord clamping.—c.w.