When to clamp the umbilical cord for full term babies?
During the last 20 years evidence has been accumulating about the benefits to the newborn of delayed clamping of the cord after birth. These benefits include increased iron stores and a decreased risk of anemia up to 4-6 months of age.1,2 Adequate availability of iron is important for the development of the brain during the first years of life3,4 and transferring the cord blood at birth is an easy way to elevate the ferritin in the blood of newborn. As an increasing number of parents are considering storing or donating their cord blood, is there a way to both benefit the baby and collect cord blood?
One difficulty when assessing the data is the inconsistency of the definitions of “early” and “delayed” clamping. “Early” has been defined as any time between 10 sec to 1 min, and “delayed” as between 30 sec to 5 min.
A systematic review and meta-analysis of the available data was performed in 2006 by Hutton and Hassan1 where they compared the outcomes in 15 clinical studies of term babies.5-19 They defined “early” as within 10-15 sec of birth and “delayed” as 2 minutes or more after birth. A similar review, also on term babies, was e-published in 2013 from the Cochrane Collaboration, authored by McDonald et al.2 Several of the studies used by Hutton were included but this analysis5-12, also included studies published between 1997 and 2012, a total of 15 studies.20-25 The definition of “early” was less than 15 sec and of “delayed” was defined as more than 1 min after birth.
The SOGC (Society of Obstetricians and Gynaecologists of Canada) addressed the timing of cord clamping in their Clinical Practice Guideline, Active management of the third stage of labour: Prevention and treatment of postpartum hemorrhage, published Oct 2009.26 They recommend the following: “Whenever possible, delaying the clamping of the cord by at least 60 seconds is preferred to clamping earlier in premature newborns (<37 weeks’ gestation)….” For term babies, they recommend caution about delaying clamping due to the possible risk of increased jaundice requiring phototherapy.
The ACOG (American Congress of Obstetricians and Gynecologists) released their updated recommendation in January 2017 and they conclude27: “Term and pre-term infants appear to derive benefit from delayed umbilical cord clamping; therefore delayed umbilical cord clamping for at least 30-60 seconds is recommended in term and pre-term infants except when immediate umbilical cord clamping is necessary because of neonatal or maternal indications.”
Both of the meta-analyses referred to above and most other published studies present data which show that delayed clamping gives newborns increased iron levels in their blood and a decreased risk for iron deficiency during the first months of life.1,2 However, as the authors point out, there was a large variation among the studies in how they evaluated iron deficiency, including how iron deficiency was defined.
Moreover, in the two meta-analyses, the difference in iron levels between the groups with early versus delayed clamping varies. One factor in these differences could be the iron status of the mother. Several of the studies included in the analyses were conducted in low and medium income settings (e.g. Argentina5, Mexico6, Libya7, India8,11) where the level of maternal care may not be the same as in North America. One study that was included in both meta-analyses has evaluated the influence of maternal iron levels6. They found that delayed clamping had a greater impact on newborn iron levels when the mother had low iron levels (defined as <9µg/L).
A group in Sweden has conducted the first modern-era long-term study of the impact of delayed cord clamping for term babies born in a country with rich resources.
Anderson et al.22 published a study on 400 term babies born in Sweden in 2011. In this study, they defined “early clamping” as within 15 sec of birth and “delayed clamping” as after 3 min, during which time they held the baby 20 cm below the vulva. At the follow up four months after birth, they found that the group with delayed clamping had significantly higher iron levels (117 µ g/L versus 81 µ g/L ), and that iron deficiency was less prevalent in the delayed clamping group, but the prevalence of anemia was the same in both groups. The authors conclude that “delayed clamping, in this randomized controlled trial, resulted in improved ferritin levels and reduced the prevalence of iron deficiency at four months of age.”
The same group published follow ups on the same babies at 12 months and 4 years of age.28,31 To our knowledge, this is the first study since 194129 to look at the effects of delayed clamping beyond 6 months. After 12 months, they found that there was no longer a difference between the groups in any of the iron status indicators, nor was there a difference in the level of anemia28.
Because adequate iron levels are important for pediatric brain development, the researchers evaluated the neurodevelopment of children in the study by asking parents to answer the Ages and Stages Questionnaire (ASQ) to assess their child’s development. This tool did not find any difference between the two groups at age 12 months and there was no correlation between neurodevelopment and iron status at birth or at 4 months28.
The neurodevelopment of the same children was again followed up at 4 years of age.31 The researchers found that, for girls, the time of clamping did not make any difference in any of the tests performed. However, boys that had early cord clamping showed slightly late development in fine motor skills and social skills. Unfortunately, this study only reported on neurodevelopment, not on iron levels or nutrition (the natural way to get iron). As neurodevelopment can be influenced by many factors, not just the level of iron at birth, further research is needed on larger groups of children to ensure that this result can be confirmed.
It has often been suggested that delayed cord clamping in full term infants could result in more instances of jaundice requiring light therapy, but this has not been proven with published data.2 In addition to clamping delay, there are other factors that influence the transfer of blood from the placenta to the baby. It has been suggested that focusing only on clamping delay and ignoring other factors such as when the baby starts breathing could be counter-productive for the infant and could even result in infant-to-placenta transfer of blood.33
It is known that it is important to prevent iron deficiency in order to achieve optimal brain development.4 While all the available data show that delayed clamping will increase the iron levels, are there any data showing that early clamping results in iron levels that are too low? This analysis is complicated by the fact that the studies are using different definitions for identifying iron deficiency and low ferritin.
Table 1 below shows iron levels of early versus delayed clamping groups in the Cochrane review.2 Using blood ferritin levels as an indicator for iron deficiency, we can see that although there are significant differences between the early versus late clamping groups, none of the groups has a mean ferritin level close to the limit of low ferritin. In the study by Andersson22, 7% of the infants that had early clamping had a ferritin level <20 µ g/L, compared with none in the delayed group. However at the 12 months follow up 1% and 2% of the infants had low ferritin levels (early and delayed clamping, respectively).28
Definition: Iron deficiency
Early: 228±147 µ g/L
Andersson 2011, 2014
>2 indicators outside ref. values
<20 µ g/L (4 m)
At 4 months:
Hemoglobin <105 g/L and ferritin <9 µ g/L
<9 µ g/L
Early: 20±26 µ g/L
Ferritin <9 µ g/L
<9 µ g/L
Early: 35±32 µ g/L
Early: 80 µ g/L (15-180)
Early: 56±4 µ g/L
It is evident that there will be less cord blood to collect if the clamping of the cord has been extensively delayed. Physiological studies in term infants have shown that approximately 70-80% of the blood in the cord and placenta is transferred in the first minute after birth16,30,38. The study by Andersson et al22 measured the remaining volume in placentas after both early and delayed clamping and found that the volume decreased by 40% when clamping was delayed for 3 minutes and the baby was held 20 cm below the vulva.
Two studies looked specifically at collected cord blood volume as a function of clamping delay. Allan et al 201636 found that a delay of 20-60 sec decreased the collection volume approximately 15%, thereby decreasing the fraction of cord blood units with a high enough cell count for public storage (defined as >1.25 billion cells) from 50% to 25% compared with units collected with no delay (<20 sec). In their study, delaying clamping even further to >120 sec, decreased the number of units with high cell counts to 14%. At the International Cord Blood Symposium in June 2016 and in the Dec. 2016 newsletter of Parent’s Guide to Cord Blood, Ciubotariu37 presented data that supported these findings. In this study, early clamping was defined as <60 sec and delayed clamping >60 sec, and they found that units with high cell content (here defined as >1.6 billion cells) decreased from approximately 18% with early clamping to approximately 2% if the clamping was delayed more than 60 sec.
Would delayed clamping still benefit the baby if the delay is only 30 sec to 1 minute? Table 2 below shows iron levels as a function of clamping delay time for two studies that provide this data. In both studies, Cernadas et al5 in Argentina and Andersson, et al32 in Sweden, there was no significant difference in blood iron levels between the early versus late clamping groups months after birth, despite variable clamping times, variable months to measurement, and delivery via C-section versus vaginal birth.
Incidence of Iron deficiency and anemia
Ferritin levels; # of infants with <9 µ g/L
At 6 months:
At 6 months:
At 4 months:
At 4 months:
- Hutton EK, Hassan ES. Late vs early clamping of the umbilical cord in full-term neonates: systematic review and meta-analysis of controlled trials. JAMA 2007; 297(11):1241-52.
- McDonald SJ, Middleton P, Dowswell T, Morris PS. Effect of timing of umbilical cord clamping of term infants on maternal and neonatal outcomes. Evidence-Based Child Health. 2014 Jun 16; 9(2):303-397 Cochrane Review Journal DOI:10.1002/ebch.1971.
- Lozoff B, Brittenham GM, Wolf AW, et al. Iron deficiency anemia and iron therapy effects on infant developmental test performance. Pediatrics 1987; 79(6):981-95.
- McCann JM, Ames BN. An overview of evidence for causal relation between iron deficiency during development and deficits in cognitive or behavioural function. Am J Clin Nutr 2007; 85(4):931-45
- Ceriani Cernadas JM, Carroli G, Pellegrini L, Ferreira M, Ricci C, Casas O, Lardizabal J, Morasso Mdel C. The effect of early and delayed umbilical cord clamping on ferritin levels in term infants at six months of life: a randomized, controlled trial. Archivos Argentinos de Pediatria 2010; 108(3):201-208.
- Chaparro CM, Neufeld LM, Tena Alavez G, Eguia-Líz Cedillo R, Dewey KG. Effect of timing of umbilical cord clamping on iron status in Mexican infants: a randomised controlled trial. Lancet. 2006; 367:1997-2004
- Emhamed MO, van Rheenen P, Brabin BJ. The early effects of delayed cord clamping in term infants born to Libyan mothers. Tropical Doctor 2004; 34(4):218-22.
- Gupta R, Ramji S. Effect of delayed clamping on iron stored in infants born to anemic mothers. Indian Pediatr 2002; 39:130-5.
- Nelson NM, Enkin MW, Saigal S, Bennett KJ, Milner R, Sackett DL. A randomized clinical trial of the Leboyer approach to childbirth. N Engl J Med 1980; 302:655-60.
- Oxford Midwifes Research Group. A study of the relationship between the delivery to cord clamping interval and the time of cord separation. Midwifery 1991; 7(4):167-76.
- Geethanath RM, Ramji S, Thirupuram S, Rao YN. Effect of timing of cord clamping on the iron status of infants at 3 months. Indian Pediatr 1997; 34:103-6.
- Saigal S, O'Neill A, Surainder Y, Chua LB, Usher R. Placental transfusion and hyperbillirubinemia in the premature. Pediatrics 1972; 49(3):406-19.
- Nelle M, Kraus M, Bastert G, Linderkamp O. Effects of Leboyer childbirth on left- and right systolic time intervals in healthy term neonates. J Perinat Med 1996; 24(5):513-20.
- Aziz et al. Early cord clamping and its effects on some hematological determinants of blood viscosity in neonates. published June 1999 on OBGYN.net and verified 2 Dec. 2016
- Grajeda R, Pérez-Escamilla R, Dewey KG. Delayed clamping of the umbilical cord improved hematological status of Guatemalan infants at 2 months of age. Am J Clin Nutr 1997; 65(2):425-431.
- Linderkamp O, Nelle M, Kraus M, Zilow EP. The effect of early and late cord clamping on blood viscosity and other haemorheological parameters in fullterm neonates. Acta Paediatr. 1992; 81(10):745-50.
- Nelle M, Zilow EP, Kraus M, Bastert G, Linderkamp O. The effect of Leboyer delivery on blood viscosity and other haemorheological parameters in term neonates. Am J Obstet Gynecol 1993; 169(1):189-93.
- Yao AC, Lind J, Vuorenkoski V. Expiratory grunting in the late clamped normal neonate. Pediatrics 1971; 48(6):865-70.
- Oh W, Lind J. Body temperature of the newborn infant in relation to placental transfusion. Acta Paediatr 1967; 56(Suppl 173):137-145.
- Jahazi A, Kordi M, Mirbehbahani NB, Mazloom SR. The effect of early and late umbilical cord clamping on neonatal hematocrit. J Perinatology 2008; 28:523-525.
- Al-Tawil MM, Abdel-Aal MR, Kaddah MA. A randomized controlled trial on delayed cord clamping and iron status at 3-5 months in term neonates held at the level of maternal pelvis. J Neonatal-Perinatal Med 2012; 5(4):319-326.
- Andersson O, Hellström-Westas L, Andersson D, Domellöf M. Effect of delayed versus early umbilical cord clamping on neonatal outcomes and iron status at 4 months: a randomised controlled trial. BMJ 2011; 343:d7157.
- Philip A. Further observations on placental transfusion. Obstr Gynecl 1973; 42(3):334-43
- Spears RL, Anderson GV, Brotman S. The effect of early vs late cord clamping on signs of respiratory distress. Am J Obstr and Gynecol 1966; 95(4):564-568.
- Van Rheenen P, de Moor L, Eschbach S, de Grooth H, Brabin B. Delayed cord clamping and hemoglobin levels in infancy: a randomized controlled trial in tern babies. Trop Med International Health 2007; 12:603-15.
- SOGC: Leduc D, Senikas V, Lalonde AB, Ballerman C, Biringer A, Delaney M, Duperron L, Girard I, Jones D, Lee LS, Shepherd D, Wilson K; Clinical Practice Obstetrics Committee; Society of Obstetricians and Gynaecologists of Canada. Active management of the third stage of labour: prevention and treatment of postpartum hemorrhage. J Obstet Gynaecol Can. 2009 Oct; 31(10):980-93.
- ACOG: The American College of Obstreticians and Gynecologists, Committee opinion. Delayed umbilical cord clamping after birth. Number 684, Jan 2017.
- Andersson O, Domellöf M, Andersson D, Hellström-Westas L. Effect of delayed vs early umbilical cord clamping on iron status and neurodevelopment at age 12 months: a randomized clinical trial. JAMA 2014; 168:547-54
- Wilson E, Windle W, Alt H. Deprivation of placental blood as a cause of iron deficiency in infants. Am J Dis Child 1941; 62(2):320-327.
- Linderkamp O. Blood rheology in the newborn infant. Baillieres Clin Haematol. 1987 Sep; 1(3):801-25.
- Andersson O, Lindquist B, Lindgren M, Stjernquist K, Domellöf M, Hellström-Westas L. Effect of delayed cord clamping on neurodevelopment at 4 years of age. A randomized clinical trial. JAMA Pediatr 2015; 169:631-38.
- Andersson O, Hellström-Westas L, Domellöf M. Elective caesarean: does delay in cord clamping for 30 s ensure sufficient iron stores at 4 months of age? A historical cohort study. BMJ Open 2016;6:e012995.
- Hooper SB, Binder-Heschl, C, Polglase GR, Gill AW, Kluckow M, Wallace EM, Blank D, te Pas AB The timing of umbilical cord clamping at birth: physiological considerations. Matern Health Neonatol Perinatol. 2016 Jun; 13:2:4.
- McAdams R. Time to implement delayed cord clamping. Commentary Obstetrics & Gynecology 2014 Mar; 123(3):549-552
- Bayer K. Delayed umbilical cord clamping in the 21st century: indications for practice. Advances in Neonatal Care 2016; 16(1):68-73
- Allan D, Scrivens N, Lawless T et al. Delayed clamping of the umbilical cord after delivery and implications for public cord blood banking. Transfusion 2016; 56(3):662-665.
- Rodica Ciubotariu, MD PhD. Timing of Umbilical Cord Clamping and Impact on Cord Blood Volume Collected for Banking. Dec. 2016 newsletter Parent;s Guide to Cord Blood Foundation
- Yao A, Hirvensalo M, Lind J. placental transfusion-rate and uterine contractions. Lancet 1968; 1:380-381