Waiting just 60 seconds to clamp umbilical cords gives very premature babies a better shot at life, reducing the risk of death and disability in the first two years of childhood by almost one-fifth, new research shows.

The Australian-led study, conducted in 25 hospitals across 7 countries, looked at health outcomes of more than 1,500 premature babies two years after they entered the world. Newborns who had their umbilical cords clamped one minute later – rather than immediately after birth – had better survival rates at two years of age.

"This is so significant as it is such a simple technique, suitable for almost all preterm babies that helps saves lives," obstetrician Jonathan Morris from the University of Sydney said in 2017 about the phenomenon, before the researchers began their latest study, tracking infant health for another two years.

By delaying cord clamping, more blood flows from the placenta to babies, with the extra red blood cells, immune cells, and stem cells thought to help newborns achieve healthy oxygen levels and control infections. This could be vital for the 1 million babies born at 30 weeks' gestation each year worldwide.

Previous research has suggested delaying cord clamping improves babies' chances of survival in the first days of life, with fewer babies dying in hospital. This latest analysis goes one step further, reporting infant health outcomes at two years of age for over 1,600 very premature babies, born 10 weeks early.

It's the largest-ever clinical trial comparing delayed and immediate cord clamping for very premature babies, born before 30 weeks and critically-ill. Maternity staff either held off clamping babies' umbilical cords for 60 seconds, or did so within 10 seconds of birth.

When the researchers combined their data on 1,531 babies with results from one other trial, taking the total to 1,637 infants, they found waiting more than 30 seconds to clamp cords reduced the relative risk of death and disability at two years of age by almost one-fifth.

Digging deeper into the results, this mostly reflects the better odds of survival newborns had if cord clamping was delayed – which reduced the relative risk of death by 30 percent – as there was no clear difference in major disability, such as cerebral palsy, vision loss, deafness, or speech problems at two years of age.

Delayed cord clamping is standard practice for full-term babies. Until recently, the umbilical cords of very premature babies were cut almost immediately after birth so the baby could receive urgent medical care.

But an Australian study, first reported in 2017, also found fewer infants needed blood transfusions after birth if cord clamping was delayed.

"Delaying cord clamping ensures that the physiological changes happening at the time of birth can happen and there are clearly very good outcomes, especially for premature babies," says midwifery expert Caroline Home of the Burnet Institute, who was not involved in the study.

The World Health Organization recommends delayed cord clamping for newborns who don't need immediate breathing support, although the practice is not always applied.

"It can be scary for clinicians to wait before they intervene," health researcher and biostatistician Anna Lene Seidler told The Sydney Morning Herald earlier this year.

A quarter of the babies in the delayed clamping group of the Australian trial actually had their umbilical cords cut before the 60-second mark, reflecting clinical concerns.

"These babies are so tiny and sick, so for clinicians not to do something straight away requires quite a rethink," said Seidler, who led another recent analysis of 42 clinical trials involving more than 5,770 babies.

That analysis found delayed cord clamping was safe and slightly improved survival, though more evidence was needed to assess alternative strategies such as cord milking.

With the evidence mounting, researchers hope that reversing the decades-old practice of clamping cords of premature babies immediately after birth could improve health outcomes in the long run for thousands of kids.

"Applied consistently worldwide, aiming to wait a minute before cord clamping in very preterm babies who do not require immediate resuscitation, could ensure that an extra 50,000 survive without major disability in the next decade," says University of Sydney biostatistician Kristy Robledo, who led the analysis.

"In other words, for every 20 very preterm babies who get delayed instead of immediate clamping, one more will survive without major disability."

More data on the timing of cord clamping from a spectrum of clinical settings would help to solidify the findings, give clinicians more confidence, rule out potential harms, and track health outcomes further into childhood.

"Intensive staff training in the new protocols will also be vital as it can be daunting to delay treatment in very early and sick babies, but the evidence suggests this results in the best outcomes for these children," says Morris.

The research was published in The Lancet Child and Adolescent Health.