NEW ORLEANS –
“We were surprised that, despite actually receiving more iron in total each day on average, the formula-fed infants were significantly more iron deficient than breast-fed babies. This is the opposite of what one would expect,” study lead author Grace Power, a medical student at Dalhousie University, Halifax, N.S., said in an interview. She presented the results at the annual meeting of the American Society of Hematology.
According to Ms. Power, there’s limited research into how breastfeeding and formula feeding affect iron levels in preterm infants – especially those born extremely early, between 23 and 30 weeks’ gestation.
“This kind of research is important because preterm infants are highly susceptible to iron deficiency for a number of reasons,” she said. “Iron deficiency early in life is associated with developmental and behavioral problems later on in life. That association still stands, even if the iron deficiency is corrected, so prevention is key in this population. Knowing more about how feeding type affects iron status can help us learn about ways to prevent iron deficiency in these infants in the future.”
For the study, researchers retrospectively analyzed data about all preterm infants (< 31 weeks gestation) in Nova Scotia from 2005 to 2018. Of the 392 infants in this group (55.75% male; average age, about 5 months), 285 were fed with iron-rich formula (mean intake, 1.66 mg/kg per day), and 107 were fully or partially breast fed. The two groups were similar in terms of traits such as mean birth weight and gestational age.
The formula-fed infants were more likely to develop iron deficiency (ID, 36.8%) than the breast-fed infants (20.6%; P = .002). “Mean gestational age and birth weight were both lower in the ID group. The ID group also had a higher percentage of infants born less than 1,100 g (P = .01). More babies in the ID group received at least one blood transfusion,” the researchers reported. “ID infants had a higher daily formula intake, daily iron intake from formula, and total daily iron intake combined from formula and supplements.”
Why is there such a gap between formula-fed infants and breast-fed infants? The researchers speculated that infants absorb less iron from formula versus breast milk, possibly because of the presence of lactoferrin in breast milk.
The researchers also wondered whether physicians may pull back on iron supplementation in infants who undergo blood transfusions out of fear of the risk of iron overload, which Ms. Power said can cause infection and poor growth. By doing so, they may inadvertently deprive the babies of their need for iron.
“We don’t want clinicians to assume an infant doesn’t need iron supplementation just because they’ve received a blood transfusion,” she said.
As for an overall message from the research, Ms. Power said clinicians “should be aware that formula feeding can put infants at risk for iron deficiency and consider this when making decisions about supplementation.” And she noted that guidelines from the American Academy of Pediatrics and Canadian Pediatric Society don’t highlight the importance of iron supplementation in formula-fed, very preterm infants.
In an interview, University of Michigan pediatrician Michael K. Georgieff, MD, who has studied iron supplementation, said the study’s primary findings are surprising, although it makes sense that infants with lower gestational age and birth weight would suffer from more ID. Blood transfusion can indeed raise iron levels, but it’s important to consider that these infants may already have low levels of iron.
Dr. Georgieff advised colleagues to understand the potential for various nutritional deficiencies in preterm infants well beyond the first few weeks. When the babies are handed off to other clinicians such as pediatricians, they should undergo nutritional screening at 6 months, not at a year.
Dalhousie University funded the study. The study authors and Dr. Georgieff have no disclosures.