Optimal cord clamping: what’s the evidence?

What’s the evidence on optimal cord clamping?

We’ve known for many years that there are many advantages to leaving the umbilical cord intact for a few minutes after birth.

Clamping and cutting the cord too early (including with shoelaces – please don’t ever do this) can deplete a baby’s iron stores and be detrimental to their health.

In premature babies, early clamping and cutting of the cord leads to a lower chance of survival.

This is important information for parents, caregivers, birth workers and others.

On this page, I share a few of the key studies that I have highlighted and written about in this area, and links to other relevant blog posts.


Delaying cord clamping for six minutes is safe

In 2021, an important study showed that it is safe to wait 6 minutes after birth, even when an oxytocic drug is given to assist with the birth of the placenta. More here:

Delaying cord clamping for six minutes is safe


Gathering the evidence

Expert researchers in this field brought together the evidence in this area in a 2021 paper.

In Cord Management of the Term Newborn, Ola Andersson and Judith Mercer summarise the key points from the available evidence.

  • “Keeping the umbilical cord intact by delaying cord clamping for at least 3 minutes improves iron stores during infancy and supports health and development for the growing child. In preterm infants, delayed cord clamping reduces mortality by approximately 30%.
  • Many midwives prefer to delay cord clamping until pulsations cease or until the placenta is ready to deliver and experience good results.
  • To warn for risk of jaundice and need for phototherapy after delayed cord clamping is not evidence based.
  • A multidisciplinary approach is critical to implement guidelines, training, and education with scheduled audits to increase compliance with delayed cord clamping.
  • Intact cord resuscitation has been practiced for centuries at midwifery births, and has shown physiologic improvements in animal and human trials.” (Andersson & Mercer 2021).

The paper covers everything from the physiology of transfusion to the most recent evidence about the optimal timing of cord clamping. Andersson & Mercer (2021) discuss giving uterotonics (RCT evidence showed no negative effects when given 3 minutes after birth). They describe optimal cord clamping at caesarean section and cord milking. The remainder of their paper is a comprehensive summary of the evidence in every area related to optimal cord clamping.


Why we need to celebrate this paper

This summary is so important. It’s not the first article on this topic, but it’s a great one, and it summarises the current evidence.

One of the reasons we need this so badly can be seen in the authors’ description of how modern medical practitioners ignored centuries old wisdom, thinking they knew better.

“Leaving the umbilical cord intact after birth has ensured our survival for millennia … In the mid twentieth century, with the advance of modern medicine, delayed [cord clamping] CC was replaced with the efficiency and expediency of immediate CC without testing for its safety. Practice was guided by expert opinion and delayed CC at birth was discarded from mainstream practice.” (Andersson & Mercer 2021).

So-called “expert opinion” is responsible for causing harm to women, babies and families in many other areas of maternity care. I’ve written about several other examples of this in my books. So it’s vital that we celebrate, share and cite papers like this one, which are based on scientific evidence and not the opinion, convenience or bias held by those who seek to control women and birth.


More on the value of leaving the cord intact

Here’s a summary of the work that Nadine Edwards and I have undertaken when we updated our book, Birthing the Placenta.

The value of leaving the umbilical cord intact


The RCOG paper (2015)

In 2015, an updated RCOG scientific impact paper added further support for delayed cord clamping. It warned that immediate cord clamping can be harmful to babies by negatively affecting their blood flow and reducing iron stores. The latter is associated with neurodevelopmental delay in babies.

The paper also acknowledges that early cord clamping, which has been a mainstay of medical management of the birth of the placenta for several decades despite a lack of evidence to support such interference, can negatively interfere with the baby’s transition from fetal to neonatal circulation.

The paper describes our current understanding of what happens physiologically in the baby’s first minutes of life, and explains why immediate cord clamping can be problematic:

“At birth, the umbilical circulation slows and pulmonary vascular resistance falls, rapidly increasing pulmonary blood flow. This is the beginning of the transition from the fetal to the neonatal circulation. Continued flow in the umbilical vein and arteries at birth may be part of the physiological mechanisms assisting the baby as it makes this transition.  Immediate cord clamping may restrict the baby’s ability to deal with the transition from the fetal to the neonatal circulation. While most healthy babies at term adapt without major consequences, for those born preterm or with their cardiorespiratory circulation already impaired, there may be an impact on clinical outcome. A brief delay in cord clamping will increase the baby’s blood volume. With a longer delay there may be other advantages, such as better cardiorespiratory transition and more stable blood pressure, and these might occur even with no further change in net blood volume.”

In the report, delayed (or deferred, as the RCOG have chosen to term it, claiming that “the previously used ‘delayed’ … might be felt to imply later than ideal”, although optimal might be an even better term) cord clamping is defined as being at least two minutes after birth, although women who want the cord to be left intact for longer than this should be supported in this.

More recent evidence suggests that a longer time frame may be preferable.

The full report can be found here and the BMJ also reported on it.


Royal College of Obstetricians & Gynaecologists. Clamping of the umbilical cord and placental transfusion: scientific impact paper No 14. 27 Feb 2015. https://www.rcog.org.uk/en/guidelines-research-services/guidelines/sip14.



How to find out more

If you’d like to know more about this and related areas, I have a whole information hub offering blog posts and articles related to the birth of the placenta, which includes optimal cord clamping. I’ve also written a book which helps women and families to better understand the evidence, so you can make the decisions that are right for you.

Andersson O & Mercer JS (2021). Cord Management of the Term Newborn. Clinics in Perinatology 48(3): 447-70. https://doi.org/10.1016/j.clp.2021.05.002.



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