Fortified breastmilk does not influence IQ in preterm infants

Children's Health

In a recent Nutrients study, scientists compare the cognitive and psychological development of preterm infants who were breastfed with or without fortification.

Study: IQ Was Not Improved by Post-Discharge Fortification of Breastmilk in Very Preterm Infants. Image Credit: pz71 / Shutterstock.com

Background

Previous studies have shown that very preterm infants are at an increased risk of cognitive deficiencies, behavioral problems, and motor impairments. Protein intake is essential for infants’ growth, as it promotes neurodevelopment.

Most available studies have focused on the nutrition and growth of hospitalized infants in the neonatal intensive care unit (NICU). These infants receive the mother’s own milk (MOM) and/or donor human milk (DHM) supplemented with multi-nutrient fortifiers that contain fat, protein, carbohydrates, and various micronutrients essential for growth.

In contrast to term formulas, preterm formulas contain a higher concentration of micro- and macronutrients that are essential for growth and cognitive improvements. Studies have shown that in preterm infants, breast milk possesses several advantages over formula due to the reduced rate of necrotizing enterocolitis (NEC), retinopathy of prematurity (ROP), reduction in bronchopulmonary dysplasia (BPD), and late-onset sepsis (LOS) in breastfed preterm infants.

Previous long-term studies have shown a positive impact of breastmilk on cognitive development at school age. To date, very few studies have assessed the role of post-discharge nutrition on preterm infants and their later development.

After discharge from the hospital, preterm breastfed infants often exhibit slower growth as compared to formula-fed infants. This suggests that exclusive breastfeeding post-discharge negatively affects the neural development of these infants. Nevertheless, more studies are needed to assess the different types of post-discharge nutrition and their effect on the future cognitive development of the child.

About the study

In the current study, researchers evaluate cognitive and neuropsychological development in a cohort that exclusively contained preterm infants who were followed up to six years of corrected age (CA). Preterm infants from four neonatal units in Denmark who were born between July 2004 and August 2008 were included in the current study. 

The study cohort included a total of 214 candidates, of which 141 breastfed infants were randomized to receive fortification (F-MOM) or not receive fortification (U-MOM), whereas the remaining 73 infants were given preterm formula (PF).

Ten to 14 days following the birth of the preterm infants, F-MOM was started and continued with reduced amounts until they were discharged from the hospital. DHM was amended if the available amount of MOM was insufficient.

The Wechsler Intelligence Scale for Children IV (WISC-IV) was used to assess intellectual ability (IQ), verbal comprehension (VC), perceptual reasoning (PR), working memory (WM), and processing speed (PS). Additionally, parents were asked to complete the Five to Fifteen (FTF) questionnaire to determine the neuropsychological and behavioral problems of their children.

Study findings

Post-discharge fortification of MOM did not have any significant effect on IQ scores at six years of age. This finding is consistent with a previous study that reported no difference in Bayley test scores at one year. However, another study reported that infants fed F-MOM exhibited better IQ scores as compared to those who received U-MOM.

Although no difference in school-aged children’s IQ scores was observed between MOM groups, a relatively higher VC index was reported when these children were compared to the PF group by 3.2 points.

Owing to ethical issues, the researchers introduced a very small amount of protein in the F-MOM group. The current study reported no significant difference in anthropometry at four months CA between the MOM groups; however, a higher amount of protein added to the F-MOM diet could alter this result.

No difference in head circumference was reported in the infants of either MOM group. However, more research is required to determine whether the fortification of breast milk with extra protein and calories has any impact on infants’ neural development and growth.

Notably, diet-based breastfeeding had a positive effect on the development of motor skills in the infants in both MOM groups as compared to infants fed with PF post-discharge.

A positive correlation was observed between IQ scores and socioeconomic groups. Interestingly, in the WISC-IV test, girls obtained better PS scores but not IQ scores, whereas boys had significantly lower scores in all domains except for emotional/behavioral problems.

Notably, previous studies contradict this result and reported that sex has less influence on the test results. However, the overall IQ scores of this study were very high in the entire group.

Conclusions

One of the key strengths of the study is the inclusion of a PF group, which helped scientists to compare cognitive development in formula and breastfed infants. Taken together, the study findings will positively help clinicians who recommend nutrition for very preterm infants upon discharge.

Journal reference:
  • Klamer, A., Toftlund, L. H., Grimsson, K., et al. (2022). IQ Was Not Improved by Post-Discharge Fortification of Breastmilk in Very Preterm Infants. Nutrients 14(13):2709. doi:10.3390/nu14132709.

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