Waiting for longer to clamp the umbilical cord of a premature baby soon after birth could help reduce the risk of death by more than half, compared with immediately clamping the umbilical cord, or waiting a shorter time before doing so, according to 2 new studies published in the journal The Lancet.

For the new findings, more than 100 international researchers examined clinical trial data and outcomes of thousands of premature babies, detailed in over 60 studies involving more than 9,000 babies.

Delaying clamping of the umbilical cord allows blood to flow from the placenta to the baby whilst the baby’s lungs fill with air. This is thought to help ease the transition to breathing in the infant.

“Worldwide, almost 13 million babies are born prematurely each year and, sadly, close to 1 million die shortly after birth. Our new findings are the best evidence to date that waiting to clamp the umbilical cord can help save the lives of some premature babies,” said Dr Anna Lene Seidler at the NHMRC Clinical Trials Centre, University of Sydney in Australia.

Delayed cord clamping is now recommended routine practice for babies born at full term. However, whilst previous research showed potential benefits for premature babies, best practices for this vulnerable group remained uncertain. Until recently, clinicians generally cut the cord of preterm babies immediately so urgent medical care could be given.

The first paper using data from 3,292 infants across 20 studies found delayed clamping of the umbilical cord, clamped 30 seconds or more after birth, likely reduced the risk of death in premature babies by a third compared to those whose umbilical cord was clamped immediately after birth.

In a subgroup of premature babies where infants were born before 32 weeks of pregnancy, 44.9 per cent of the babies with immediate cord clamping experienced hypothermia after birth, compared to 51.2 per cent of those with delayed clamping. The average difference in temperature between the deferred clamping group and the immediate clamping group was -0.13 °C.

The second paper analysed data from 47 clinical trials, which involved 6,094 babies, and found waiting at least two minutes before clamping the cord of a premature baby may reduce the risk of death compared with waiting less time to clamp the cord.

In comparing different timings, waiting two or more minutes to clamp the cord had a 91 per cent probability of being the best treatment to prevent death shortly after birth.

Immediate clamping had a very low (below 1 per cent) probability of being the best treatment for preventing death.

However, the researchers highlight situations where more research is needed on cord clamping. This includes when there are babies requiring immediate resuscitation, unless the hospital is able to provide safe initial breathing help with the cord intact, or in a low-income setting with limited medical resources.