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By Maggie Fox

Can waiting for a few minutes to cut or clamp the umbilical cord make a child smarter?

Not really, researchers reported Tuesday — but it seems to be safe and it may help babies who are most at risk of brain damage.

Advocates of delayed cord clamping or cutting say it gives time for the baby to get some extra blood out of the placenta — blood that is rich in iron and other nutrients important for a young, developing brain.

Dr. Ola Andersson of Uppsala University in Sweden and colleagues checked out 263 children. Out of that group, 141 of them had been given about three minutes before the umbilical cord was clamped.

“This is one of the first studies to show that as early as 4 years, one can see a measurable difference."

The team ran neurological and other tests on the kids when they turned 4.

"Delaying cord clamping for three minutes after delivery resulted in similar overall neurodevelopment and behavior among 4-year-old children compared with early cord clamping,” they wrote in their report, published in the Journal of the American Medical Association.

But they did find some very subtle benefits in some children.

“However, we did find higher scores for parent-reported prosocial behavior as well as personal-social and fine-motor development at 4 years, particularly in boys. The included children constitute a group of low-risk children born in a high-income country with a low prevalence of iron deficiency.”

In other words, it was having a subtle effect in some children born to well-off parents.

“This is one of the first studies to show that as early as 4 years, one can see a measurable difference,” said Dr. Tonse Raju of the National Institute of Child Health and Human Development, who was not involved in the study. “As far as I am concerned, this is very significant.”

Dr. Heike Rabe of the Brighton and Sussex Medical School and University Hospitals in Britain agreed.

“While many physicians have incorporated delayed cord clamping into practice, there remains a hesitation to implement delayed cord clampig, particularly with full-term infants,” Rabe and colleagues wrote in a commentary.

“As evidence of the safety and benefits of delayed cord clamping are demonstrated, this hesitation should disappear,” they added.

"We applaud Andersson and colleagues for their persistence because their study closes the knowledge gap regarding the long-term safety of delayed cord clamping in healthy full-term newborns. Their important findings suggest that there is an absence of harm that lasts until 4 years of age.”

The question is what effect would it have in children at higher risk of low iron anemia?

The World Health Organization already recommends waiting at least a minute after deliver to clamp or cut the cord. While there's not a whole lot of blood left in the cord, it can mean a lot to someone as tiny as a newborn.

But U.S. groups such as the American College of Obstetricians and Gynecologists say the evidence is mixed, and argue that waiting could endanger the baby and the mother. One of the biggest objections is the risk of jaundice. Newborn livers cannot process extra red blood cells as well.

But Raju says all newborns need to be watched for jaundice and treated if necessary anyway. He says this study starts to tip the balance in favor of waiting, even in the U.S.

“As many as 10 percent of children may be borderline iron-deficient,” Raju said.

Foods are supplemented, but babies are supposed to get nothing but breast milk until they are 6 months old, and human breast milk is not the richest source of iron. Iron deficiency in early childhood can strongly affect brain development.

“As many as 10 percent of children may be borderline iron-deficient."

The NICHD, part of the National Institutes of Health, is paying for a similar study right now in San Diego, Raju said.

“Possibly, there is a group of children who are likely to be at risk, particularly children from lower socioeconomic strata,” Raju said.