Can Cutting the Umbilical Cord Later Make Boys Smarter? Study Suggests It Can

A new study suggests that a delay in clamping the cord in newborn boys may improve motor skills and social skills needed later on in childhood, according to a new study.

Previous studies have also shown that cord clamping has other benefits for newborns, such as increased iron levels in the blood.

"There is quite a lot of brain development just after birth," said lead author Dr. Ola Andersson of Uppsala University in Sweden. "Iron is needed for that process."

For the new study, the researchers followed up on 263 Swedish children born at full term to healthy mothers about four years earlier.

"There is growing evidence from a number of studies that all infants, those born at term and those born early, benefit from receiving extra blood from the placenta at birth," said Dr. Heike Rabe, a neonatologist at Brighton & Sussex Medical School in the United Kingdom. Rabe's editorial accompanied the study published Tuesday in the journal JAMA Pediatrics.

"The extra blood at birth helps the baby to cope better with the transition from life in the womb, where everything is provided for them by the placenta and the mother, to the outside world," Rabe said. "Their lungs get more blood so that the exchange of oxygen into the blood can take place smoothly."

"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."