The common practice of immediate cord clamping, which generally means clamping within 15-20 seconds after birth, was fueled by efforts to reduce the risk of postpartum hemorrhage, a leading cause of maternal death worldwide. Immediate clamping was part of a full active management intervention recommended in 2007 by the World Health Organization, along with the use of uterotonics (generally oxytocin) immediately after birth and controlled cord traction to quickly deliver the placenta.
Adoption of the WHO-recommended “active management during the third stage of labor” (AMTSL) worked, leading to a 70% reduction in postpartum hemorrhage and a 60% reduction in blood transfusion over passive management. However, it appears that immediate cord clamping has not played an important role in these reductions. Several randomized controlled trials have shown that early clamping does not impact the risk of postpartum hemorrhage (> 1000 cc or > 500 cc), nor does it impact the need for manual removal of the placenta or the need for blood transfusion.
Instead, the critical component of the AMTSL package appears to be administration of a uterotonic, as reported in a large WHO-directed multicenter clinical trial published in 2012. The study also found that women who received controlled cord traction bled an average of 11 cc less – an insignificant difference – than did women who delivered their placentas by their own effort. Moreover, they had a third stage of labor that was an average of 6 minutes shorter (Lancet 2012;379:1721-7).
With assurance that the timing of umbilical cord clamping does not impact maternal outcomes, investigators have begun to look more at the impact of immediate versus delayed cord clamping on the health of the baby.
Thus far, the issues in this arena are a bit more complicated than on the maternal side. There are indications, however, that slight delays in umbilical cord clamping may be beneficial for the newborn – particularly for preterm infants, who appear in systemic reviews to have a nearly 50% reduction in intraventricular hemorrhage when clamping is delayed.
Timing in term infants
The theoretical benefits of delayed cord clamping include increased neonatal blood volume (improved perfusion and decreased organ injury), more time for spontaneous breathing (reduced risks of resuscitation and a smoother transition of cardiopulmonary and cerebral circulation), and increased stem cells for the infant (anti-inflammatory, neurotropic, and neuroprotective effects).
Theoretically, delayed clamping will increase the infant’s iron stores and lower the incidence of iron deficiency anemia during infancy. This is particularly relevant in developing countries, where up to 50% of infants have anemia by 1 year of age. Anemia is consistently associated with abnormal neurodevelopment, and treatment may not always reverse developmental issues.
On the negative side, delayed clamping is associated with theoretical concerns about hyperbilirubinemia and jaundice, hypothermia, polycythemia, and delays in the bonding of infants and mothers.
For term infants, our best reading on the benefits and risks of delayed umbilical cord clamping comes from a 2013 Cochrane systematic review that assessed results from 15 randomized controlled trials involving 3,911 women and infant pairs. Early cord clamping was generally carried out within 60 seconds of birth, whereas delayed cord clamping involved clamping the umbilical cord more than 1 minute after birth or when cord pulsation has ceased.
The review found that delayed clamping was associated with a significantly higher neonatal hemoglobin concentration at 24-48 hours postpartum (a weighted mean difference of 2 g/dL) and increased iron reserves up to 6 months after birth. Infants in the early clamping group were more than twice as likely to be iron deficient at 3-6 months compared with infants whose cord clamping was delayed (Cochrane Database Syst. Rev. 2013;7:CD004074)
There were no significant differences between early and late clamping in neonatal mortality or for most other neonatal morbidity outcomes. Delayed clamping also did not increase the risk of severe postpartum hemorrhage, blood loss, or reduced hemoglobin levels in mothers.
The downside to delayed cord clamping was an increased risk of jaundice requiring phototherapy. Infants in the later cord clamping group were 40% more likely to need phototherapy – a difference that equates to 3% of infants in the early clamping group and 5% of infants in the late clamping group.
Data were insufficient in the Cochrane review to draw reliable conclusions about the comparative effects on other short-term outcomes such as symptomatic polycythemia, respiratory problems, hypothermia, and infection, as data were limited on long-term outcomes.
In practice, this means that the risk of jaundice must be weighed against the risk of iron deficiency. In developed countries we have the resources both to increase iron stores of infants and to provide phototherapy. While the WHO recommends umbilical cord clamping after 1-3 minutes to improve an infant’s iron status, I do not believe the evidence is strong enough to universally adopt such delayed cord clamping in the United States.