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Cutting the cord: babies benefit from a delay

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Research by Dr Judith Mercer of the University of Rhode Island shows that babies who remained connected to their umbilical cord for longer had healthier blood days and months later.

When a baby is born, how quickly should the midwife cut the umbilical cord? For decades, scientists and health care professionals have had very different views on exactly when this procedure should happen.

Normal western practice has been to cut the baby’s cord within a minute of birth. In the US, it tends to be quicker, unless the baby is premature. In the UK, the current advice is to cut it after a minute.

Striking new evidence suggests that a five-minute delay in cutting the umbilical cord could be very beneficial to the health of newborn babies. The recent study by Dr Judith Mercer, from the University of Rhode Island in the US, could have major implications for the way we deliver babies in the future.

Effects of A Five Minute Delay with Infants Placed on the Maternal Abdomen
Mercer and her team compared a random sample of babies that had an immediate cord clamping operation (ICC, within 20 seconds) with babies that continued to receive oxygen-rich blood via an intact umbilical cord. In these cases, the cord was not severed until five minutes after the birth, allowing ongoing placental transfusion of vital red blood cells. If the provider felt they could not wait, they were instructed to milk the cord.

Results Two Days Later
Her researchers monitored the effects of the two different strategies. Even 48 hours later, the babies that experienced delayed cord clamping (DCC) had significantly higher blood levels of the protein haemoglobin. Haemoglobin contains iron, a critical element for early development. A higher haemoglobin level is usually a proxy for more blood volume.

During birth, babies’ lungs must change in function from an organ that produces fluid to one that allows gas exchange. To facilitate this, the proportion of blood flowing to the lungs increases from 8–10% to around 45%. ICC reduces the amount of blood available to the newborn, meaning that the baby’s body draws blood from other reservoirs, potentially at the cost of other organs, which may consequently underperform.

Delayed cord clamping may have continuing benefits for
the early development of white matterQuote_brain

One of the reasons that some of those who currently practise ICC do so is to minimise the risk of severe jaundice in the baby (80% of all newborns experience some jaundice). This is caused by excess bilirubin in the blood. Bilirubin is naturally produced by the body as it breaks down old red blood cells and is protective at normal newborn levels. However, excessively high levels can be extremely harmful, and may even lead to brain damage. Some doctors had been worried about other possible harmful effects on the newborn’s blood but Mercer’s experiments (and others) found no evidence that DCC increased the risk of conditions such as polycythaemia, hyperviscosity, or transient tachypnea, all of which, like jaundice, are supposedly avoided by implementing ICC.

Mercer’s study found no increase in bilirubin levels in two-day old babies who had undergone DCC, suggesting that DCC does not increase the risk of hyperbilirubinaemia (excessively high levels of bilirubin).

Four Month Results
At four months, infant ferritin levels were measured. Ferritin is the main iron-storage protein in the body so testing ferritin is a good indication of iron levels. They also underwent MRI scanning using a novel myelin-imaging technique that can quantify the amount of myelin (wrapping of nerve cells) in the brains of newborns. Mercer’s team was looking for any association between higher ferritin levels and myelin content. All MRI scans were done in the evening during non-sedated sleep.

Infants in the DCC group had higher ferritin levels and a positive relationship between ferritin and myelin content in areas that are important for sensory processing and motor function. Babies who had had DCC had more myelin in these same areas than the infants with ICC. This suggests that delayed cord clamping may have continuing benefits for the early development of white matter (brain tissue important for learning and brain function).

Plans for One and Two Years
Mercer plans to assess the study children at one and two years of age with repeated MRI scans and development testing. All children will have reached one year of age by November 2016. That data should be ready for publication in the spring of 2017. The same follow-up is planned for two years of age as well.

Championing Delayed Cord Clamping
Mercer has been an advocate of DCC for much of her career. ‘I adopted the practice of delaying cord clamping to ensure a more gentle birth and have used it for more than 30 years,’ she has previously told the Science and Sensibility website. Mercer was awarded the highest honour of the American College of Nurse-Midwives, the Hattie Hemschemeyer Award, in 2014.

She recounts an early clinical experience with a baby boy born with his umbilical cord wrapped tightly around his neck. In this instance, the baby was born pale and limp. In a hospital, the tight cord would have been cut immediately and the baby put on a warmer or resuscitaire to be resuscitated. Instead, Mercer simply unwrapped the cord and allowed the highly oxygenated blood to flow naturally.

‘In about one and a half minutes, he flexed his extremities, opened his eyes and took a gentle breath. He nursed very well and was a normal child at one year of age when I last saw him,’ she said.

Lack of Iron
Mercer’s research is supported by other recent studies across the world that hint at DCC’s far-reaching benefits. It has been suggested that higher iron content in early life is connected to better coordination and social skills in later life and that developmental issues like ADHD are linked to less brain myelin.

Iron is crucial to early brain development, particularly in areas responsible for sensory processing and motor function. It is essential for the formation of oligodendrocytes in the brain. Oligodendrocytes are cells that are key for myelin formation, the development of the fatty sheath around brain cells that is essential to their function.

While questions about the timing of cord clamping linger, in premature deliveries DCC has been shown to lower the risk of bleeding in the brain as well as the need for transfusions. Preterm infants are very susceptible to the harmful effects of low blood pressure in the first 24 hours of life. DCC has been shown to raise blood pressure in these tiny babies during that critical period.

Although the long-term effects of ICC on the infant were not studied until recently, Mercer showed an advantage to preterm infants at 18 months of age in an earlier study and Dr Ola Andersson from Sweden found advantages for children at 4 years of age who had DCC as babies. Many experienced midwives had been advocating DCC in order to promote a more relaxed, natural transition from the pre-natal world. In the past this attitude has been frowned upon in some hospital settings, says Mercer.

The importance of the timing of cord clamping is shown by the physiological figures: delaying by just three minutes allows an extra 100 ml of blood to travel along the cord to the baby. Relatively speaking, this is equivalent to just under 2 litres of blood for an adult; the effect of leaving the cord intact at such a vital time could be very significant.

‘Birth is perhaps the most dramatic physiologic event any human will experience,’ says Mercer. ‘How it is conducted may have effects that will last a lifetime. Evidence is building that the current practice of immediate cord clamping is creating harm.’

More information:

Why is it common practice to cut the umbilical cord so swiftly?
The main reason is for expediency. Also, people think that the neonatologist can ‘fix’ whatever is wrong with a newborn. Many studies are showing that these infants would do better if they received their cord blood before breathing and cord clamping.

Should an expectant mother be worried about the timetable of her birth?
She should take steps to ensure that her infant will receive delayed cord clamping or cord milking at birth. The baby’s father can help to confirm that a delay happens at the birth.

Many studies are showing that these infants would do better if they received their cord blood before breathing and cord clampingQuote_brain

Is a delayed clamping always better?
Yes. This is basic blood volume that the infant was using for respiration in the uterus. S/he needs it after birth for independent respiration. Also, it is filled with many stem cells that have been shown to help with healing the newborn and may be extremely important over one’s lifetime.

Can a mother request a delay?
Yes, she can and she should.

Are there still risks associated with a delay?
No. We have three meta-analyses involving delayed cord clamping with term infants, preterm infants and both with cord milking. A meta-analysis combines data from many studies. None of the meta-analyses, or any of the individual studies show harm to the infants.

Research Objectives
Dr Mercer’s experience as a midwife has informed her research into cord clamping. Her work shows that a 5-minute delay in cord clamping can have long-lasting benefits to the term infant.

National Institutes of Health (NIH)


  • Research partner: Dr Debra Erickson-Owens
  • Dr Sean Deoni
  • Dr James Padbury
  • Dr William Oh
  • Dr Betty Vohr
  • Richard Tucker, BA

mercer-pictureJudith Mercer was educated at University of Maryland, Columbia University, and Catholic University of America. Her first career as a midwife (30 years) led to her second career as a funded researcher studying the effects of delaying cord clamping on the newborn. She is a research scientist at Women & Infants Hospital in Providence, Rhode Island and Professor Emerita at the University of Rhode Island.

Judith Mercer, PhD, CNM, FACNM
Women & Infants Hospital
Pediatric Research
101 Dudley St
Providence, Rhode Island, RI 02905

E: [email protected]
T: +1 401 480 1542

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