Effect of timing of umbilical cord clamping on iron status in Mexican infants: a randomised controlled trial

Lancet. 2006 Jun 17;367(9527):1997-2004. doi: 10.1016/S0140-6736(06)68889-2.


Background: Delayed clamping of the umbilical cord increases the infant's iron endowment at birth and haemoglobin concentration at 2 months of age. We aimed to assess whether a 2-minute delay in the clamping of the umbilical cord of normal-weight, full-term infants improved iron and haematological status up to 6 months of age.

Methods: 476 mother-infant pairs were recruited at a large obstetrics hospital in Mexico City, Mexico, randomly assigned to delayed clamping (2 min after delivery of the infant's shoulders) or early clamping (around 10 s after delivery), and followed up until 6 months postpartum. Primary outcomes were infant haematological status and iron status at 6 months of age, and analysis was by intention-to-treat. This study is registered with ClinicalTrials.gov, number NCT00298051.

Findings: 358 (75%) mother-infant pairs completed the trial. At 6 months of age, infants who had delayed clamping had significantly higher mean corpuscular volume (81.0 fL vs 79.5 fL 95% CI -2.5 to -0.6, p=0.001), ferritin (50.7 mug/L vs 34.4 mug/L 95% CI -30.7 to -1.9, p=0.0002), and total body iron. The effect of delayed clamping was significantly greater for infants born to mothers with low ferritin at delivery, breastfed infants not receiving iron-fortified milk or formula, and infants born with birthweight between 2500 g and 3000 g. A cord clamping delay of 2 minutes increased 6-month iron stores by about 27-47 mg.

Interpretation: Delay in cord clamping of 2 minutes could help prevent iron deficiency from developing before 6 months of age, when iron-fortified complementary foods could be introduced.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anemia, Iron-Deficiency / prevention & control*
  • Constriction
  • Female
  • Ferritins / blood*
  • Fetal Blood / chemistry*
  • Humans
  • Infant
  • Infant Food
  • Infant, Newborn
  • Iron / blood*
  • Male
  • Mexico
  • Time Factors
  • Umbilical Cord / blood supply*


  • Ferritins
  • Iron

Associated data

  • ClinicalTrials.gov/NCT00298051