A standard iron supplementation plan may not fully satisfy the needs for preterm infant catch-up growth due to the wide variation in total iron content in preterm infants.
This is according to a prospective follow-up study on preterm infants in Sichuan’s West China Second University Hospital.
“Postnatal iron supplementation at 2–4 mg/kg/d in preterm infants significantly decreases the incidence of iron deficiency; however, iron supplementation based on a single standard may not fully satisfy the need for early preterm infant catch-up growth because of the multitude of factors affecting preterm iron stores and the wide variation in total iron content in preterm infants,” wrote researchers in BMC Pediatrics.
Iron deficiency is the most prevalent nutritional deficiency disease in preterm infants, significantly affecting their growth and development.
For preterm infants to flourish physically and neurologically, timely iron supplementation is essential.
According to the Chinese Pediatric Association’s Recommendations for Prevention and Control of Iron Deficiency and Iron Deficiency Anemia in Children, preterm infants were given iron supplements (2–4 mg/kg/d) between two weeks and twelve months of age after delivery.
However, current guidelines are based on studies of iron status in early preterm infants – gestational age of less than 34 weeks.
There are also few studies on iron status in late preterm infants and in preterm infants of various gestational ages.
Researchers therefore set out to evaluate whether the present iron supplementation regimen could meet the iron demand of early preterm infants. They also assessed if the current supplemental dosage resulted in iron overload in late preterm infants.
The study
In the study, 177 preterm infants were divided into two groups based on gestational age.
The first group had 70 early preterm infants with gestational age of less than 34 weeks.
The second group had 107 late preterm infants with gestational age of 34 weeks to 37 weeks.
They were all receiving 2–4 mg/kg/d iron supplements.
The infants were assessed at three time points – during the corrected gestational ages of three, six, and 12 months.
Corrected gestational age was calculated by subtracting the remaining weeks to reach the full term of 40 weeks.
To compare iron metabolism and physical growth indicators of these infants, the following data were collected: feeding status, blood counts, iron metabolism markers, and body measurements.
Researchers discovered that the levels of ferritin – a protein that stores iron within cells – were considerably lower in early preterm infants at corrected three months of age compared to late preterm infants.
The ferritin levels for early preterm infants at three months was 31.57 ng/mL on average. For late preterm infants at the same age, it was 65.78 ng/mL on average.
This indicates that even with iron supplementation of 2–4 mg/kg/d, early preterm infants do not have as much iron as late preterm infants by the time of the corrected gestational age of 3 months.
The researchers also compared preterm infants with iron deficiency and those without at six months old. They found that preterm infants with iron deficiency had considerably lower levels of certain biomarkers.
For example, iron deficient preterm infants had lower levels of haemoglobin and ferritin at an average of 116.56 g/L and 8.01 g/L respectively; while those without iron deficiency had an average of 123.7 g/L haemoglobin and 37.71 g/L ferritin.
Iron is a key component of haemoglobin. A lack of iron will lead to reduced haemoglobin, resulting in iron deficiency anaemia.
Additionally, the researchers said there are other factors to consider, such as how the low levels of ferritin in preterm infants could affect how iron was metabolised.
For term infants, iron stores fulfil metabolic requirements until approximately 4–6 months of age. Therefore, ferritin is significantly depleted and gradually declines in term infants between three and six months.
“This change in ferritin was not observed in early preterm infants, which may be because preterm infants have insufficient stored iron from birth, the ferritin in the body continues to be at a lower level and there is not enough stored iron to be consumed. Therefore, we hypothesised that the iron status of late preterm infants may be closer to that of term infants and quite different from that of early preterm infants,” said the researchers.
It was also found that increasing the iron supplementation dose would increase ferritin concentration in the blood.
Therefore, uniformly supplementing preterm infants with 2–4 mg/kg/day iron may not be able to meet the early catch-up growth needs of very early preterm infants, especially ultra early preterm infants.
This may also result in iron overload and related side effects in late preterm infants with heavier birth weights and older gestational ages who are not at high risk for other iron deficiency factors.
“For preterm infants, a tailored iron supplementation plan based on growth, birth weight, and gestational age may be a more suitable route for iron supplementation,” concluded the researchers.
Source: BMC Pediatrics
DOI: 10.1186/s12887-024-04996-5
“The effect of iron supplementation in preterm infants at different gestational ages”
Authors: Sufeng Ruan, Jinrong Li et al.
