Effect of Delayed vs Early Umbilical Cord Clamping on Iron Status and Neurodevelopment at Age 12 Months A Randomized Clinical Trial

IMPORTANCE Prevention of iron deficiency in infancy may promote neurodevelopment. Delayed cord clamping (DCC) can prevent iron deficiency during the first 6 months of life. However, no data are available on long-term effects on infant outcomes in relation to time for umbilical cord clamping. OBJECTIVE To investigate effects of DCC, as compared with early cord clamping (ECC), on infant iron status and neurodevelopment at age 12 months in a European setting. DESIGN, SETTING, AND PARTICIPANTS Randomized clinical trial of 382 full-term infants born after a low-risk pregnancy at a Swedish county hospital. Follow-up at 12 months included evaluation of iron status (ferritin level, transferrin saturation, transferrin receptor level, reticulocyte hemoglobin level, and mean cell volume) and parental assessment of neurodevelopment by the Ages and Stages Questionnaire, second edition (ASQ). INTERVENTIONS Infants were randomized to DCC (>= 180 seconds after delivery) or ECC (<= 10 seconds after delivery). MAIN OUTCOMES AND MEASURES The main outcome was iron status at age 12 months; the secondary outcome was ASQ score. RESULTS In total, 347 of 382 infants (90.8%) were assessed. The DCC and ECC groups did not differ in iron status (mean ferritin level, 35.4 vs 33.6 ng/mL, respectively; P =.40) or neurodevelopment (mean ASQ total score, 229.6 vs 233.1, respectively; P =.42) at age 12 months. Predictors of ferritin levels were infant sex and ferritin in umbilical cord blood. Predictors of ASQ score were infant sex and breastfeeding within 1 hour after birth. For both outcomes, being a boy was associated with lower results. Interaction analysis showed that DCC was associated with an ASQ score 5 points higher among boys (mean [SD] score, 229 [43] for DCC vs 224 [39] for ECC) but 12 points lower among girls (mean [SD] score, 230 [39] for DCC vs 242 [36] for ECC), out of a maximum of 300 points (P =.04 for the interaction term). CONCLUSIONS AND RELEVANCE Delayed cord clamping did not affect iron status or neurodevelopment at age 12 months in a selected population of healthy term-born infants. However, it may not be possible to demonstrate minor effects on neurodevelopment with the size of the study population and the chosen method for assessment. The current data indicate that sex may influence the effects on infant development after DCC in different directions. The magnitude and biological reason for this finding remain to be investigated.