Delayed Clamping of the Umbilical Cord: A Review with Implications for Practice

Gina Eichenbaum-Pikser, CNM, MSN; Joanna S. Zasloff, CNM, MSN


J Midwifery Womens Health. 2009;5(4):321-326. 

In This Article

Benefits of Delayed Cord Clamping

Hemoglobin and Hematocrit Values

In term newborns, waiting 1 to 3 minutes after birth to clamp the umbilical cord has been shown to result in an increase in neonatal Hct and Hgb levels,[3,9] which results in a significantly lower proportion of infants with anemia.[8,9] In an RCT of term infants born to mothers without prenatal or obstetric complications, Cernadas et al.[9] compared the venous Hct of 276 newborns, allocated either to cord clamping at 15 seconds, 1 minute, or 3 minutes after birth. At 6 hours of life, Hct values were significantly lower in the infants allocated to the early clamping group versus the 1- and 3-minute groups (53.5%, 57%, and 59.4%, respectively.)[9] At 24 to 48 hours of life, the difference continued to be significant, with Hct levels of 51.4%, 53.62%, and 56.41% for the 15-second and 1- and 3-minute groups, respectively.

In a metaanalysis of 15 controlled trials of full-term infants (n = 1912), Hutton and Hassan[2] found that as early as 7 hours after birth, mean neonatal Hgb levels measured in capillary blood are higher in newborns with late clamping.[2] Neonatal Hct levels were significantly higher at 24 to 48 hours after birth when cord clamping was delayed for a minimum of 2 minutes.[2] Perhaps more importantly, this difference continued to be significant between 2 months after birth and 6 months after birth (weighted mean difference [WMD], 3.7%; 95% confidence interval [CI], 2.0%–5.4%). At 6 months, no difference remained between the two groups.

Similarly, three trials (n = 671) included in McDonald and Middleton's[3] Cochrane metaanalysis, found significantly lower infant Hgb levels at birth (WMD, -2.17; 95% CI, -4.06 to -0.28) and again at 24 hours in infants in early clamping groups (WMD, -1.34 g/dL; 95% CI, -1.88 to -0.88; 2 trials; n = 382). While McDonald and Middleton's[3] metaanalysis describes one trial in which a favorable effect was found in Hgb values at 2 to 4 months, there was no difference when all three trials in the review were combined.[3]

Ferritin Levels

When compared with early clamping, delayed cord clamping has been shown to significantly increase neonatal iron stores.[2,3] Hutton and Hassan[2] found that ferritin levels at 2 to 3 months of age were higher in infants allocated to late clamping versus early clamping (2 trials; n = 144; WMD, 17.89 mcg/L; 95% CI, 16.58–19.21) and estimated a 33% reduction in the risk of having deficient iron stores at that age. Two trials, with a total of 165 infants, found that fewer infants in the late clamping group had ferritin levels < 50 mg/L at 3 months of age (relative risk [RR], 0.67; 95% CI, 0.47–0.96).[2] One trial of 107 infants, included in McDonald and Middleton's[3] Cochrane metaanalysis, also showed ferritin levels were significantly higher in the late clamping group at age 3 months (WMD, 17.90 mcg/L; 95% CI, 16.59–19.21).[3] Interestingly, at 6 months in a different trial of 315 infants, ferritin levels continued to be significantly higher than those with early clamping (WMD, 11.80 mcg/L; 95% CI, 4.07–19.53). In this same trial, none of the infants in the late clamping groups versus six in the early clamping group were diagnosed with iron deficiency.[2]

Compared with immediate clamping, delaying cord clamping for 3 minutes provides an additional blood volume of approximately 20 mL/kg to the newborn.[7,9] This has been shown to provide an additional 40 to 50 mg/kg of iron and an increase in packed cell volume.[7,8,9] This is especially relevant when considering that iron deficiency is the primary cause of anemia which, early in life, can lead to marked central nervous system effects and cognitive impairment.[9] In addition, delayed cord clamping can increase the rate of transfer of hematopoietic stem cells to the newborn, which may play a role in the prevention of certain blood disorders and immune conditions[9] and a clinically significant reduction in anemia (RR, 0.53; 95% CI, 0.40–0.70).[2]


Increased infant Hct and Hgb levels result in a reduced risk of anemia during infancy. In three separate trials, Hutton and Hassan[2] found that the risk of anemia (defined as a Hgb < 10 g/dL or Hct < 46%) was decreased with late clamping at 24 to 48 hours (RR, 0.20; 95% CI, 0.06–0.60; 1 trial; n = 179) and at 2 to 3 months (RR, 0.53; 95% CI, 0.4–0.7; 2 trials; n = 119). The authors estimated a significant 47% reduction in the risk of anemia when late clamping was employed.[2] Cernadas et al.[9] found that there were significantly more infants with a Hct level of < 45% from the 15-second clamping group than the 1-minute (RR, 0.13; 95% CI, 0.035–0.50) or 3-minute groups (RR, 0.20; 95% CI, 0.06–0.61). McDonald and Middleton's[3] Cochrane meta-analysis supports this finding. When defined as a Hct of < 45%, fewer infants in the late clamping group had anemia at 24 to 48 hours after birth.[2] At 6 months, this difference was no longer apparent.