Iron supplements may help boost brain development and ward off behavioural problems in babies who are born a bit on the small side, a new study from Sweden suggests.
Low birth-weight babies are more likely to end up iron deficient, researchers said. They need more of the nutrient for catch-up growth and haven't stored as much as other babies if they're also born premature.
For that reason, very early-term and very small babies are often put on iron - but less research has looked at babies born just shy of normal weight, to see if they are also at risk.
"I think this further solidifies the evidence that it's a very good idea to give these (marginally low birth-weight) children iron supplements," said Dr Magnus Domellof, from Umea University, who worked on the study.
The research was led by his colleague, Dr Staffan Berglund. Their team followed 285 infants born between 4 pounds, 7 ounces and 5 pounds, 8 ounces (2kg to 2.5kg).
When the babies were six weeks old, the researchers randomly assigned them to get iron drops - either one or two milligrams per kilogram of body weight - or iron-free placebo drops each day until their six-month birthday.
Then at age three and a half, Domellof's team brought the kids back for IQ tests and surveyed parents about their behavioral issues. The researchers compared kids in the iron- and placebo-drop study groups with another 95 children who were born at normal weight.
There were no IQ differences based on whether the smaller-than-average babies had been put on an iron regimen. All three low birth-weight groups had average scores between 104 and 105. ("Cognitive impairment" in this study was considered an IQ under 85.)
However, significantly more babies given placebo drops had behavioural problems, as reported by their parents. The issues included problems managing emotional reactions, anxiety and depression, as well as sleep and attention problems.
Almost 13 per cent of the placebo-group babies scored above the cut-off for clinical behaviour problems, versus about 3 per cent of kids who'd taken iron drops and kids from the normal-weight comparison group.
That suggests iron deficiency in infancy may be a direct cause of behavioural problems later in childhood, the researchers wrote Monday in the journal Pediatrics.
They are continuing to monitor the same group of kids as they get older, to see if new cognitive or behavioural problems develop or old ones get better as the children head into grade school.
Domellof said he and his colleagues didn't see any extra stomach problems in kids or delayed growth linked to the use of iron drops. Some research has suggested giving excessive iron to young kids who aren't deficient may stunt their development.
But, "I would not be afraid of recommending this to all children (born) below 2,500 grams (5 pounds, 8 ounces) at this dose," Domellof told Reuters Health.
"Here's where an ounce of prevention is worth a pound of cure," said Dr Michael Georgieff, a child development researcher at the University of Minnesota in Minneapolis who had reviewed the study as part of Berglund's dissertation committee.
He told Reuters Health that it's important for all parents to know their baby's iron requirements when they leave the hospital.
"The issue with these marginally low birth-weight infants is, people really haven't paid a lot of attention to them, but the evidence is accumulating that they are at risk for behavioural problems and less than ideal cognitive function," said Dr Betsy Lozoff, who studies the effects of iron deficiency in infants at the University of Michigan in Ann Arbor.
For most babies in the United States, extra iron is recommended starting at four to six months, either through supplements if the mother is breastfeeding or through formula. Very small or premature babies typically have their iron monitored from birth.
But Lozoff, who wasn't involved in the new research, said that in many places, there are no recommendations for how to treat babies who are just below a normal birth weight.
"This would suggest that it should just be a routine supplementation, and it can be at a low level of iron," she told Reuters Health.