Rapid weight gain may have cognitive advantages for preterm infants

The modest neurodevelopmental benefits of rapid weight gain for preterm infants during the first year of life offset the small risk of developing high blood pressure in the future, recent study results indicate.

Researchers from several institutions in Boston used data from the Infant Health and Development Project (IHDP) — an eight-center longitudinal study of infants born at 37 weeks or fewer with birth weights of 2,500 g or less — to examine potential links between rapid infant weight gain and better neurodevelopmental outcomes and higher BP.

The study sample comprised 911 infants, according to the researchers, with a median birth weight of 1.87 kg and a median gestational age of 34 weeks. After correcting age for prematurity, IHDP staff weighed the infants at term, 4 and 12 months of age. They measured BP three times at 6.5 years and IQ using the Wechsler Intelligence Scale for Children-III (WISC-III) at 8 years. The researchers also adjusted for several covariates, including sex, age and race of the child, as well as maternal education, income, age, IQ and smoking.

Results showed that mean ± standard deviation systolic BP was 104.2 ± 8.4 mm Hg at 6.5 years; mean ± WISC-III score was 91 ± 18 points at 8 years; and median weight z score was –0.7 at 12 months. The researchers said more rapid infant weight gain correlated with slightly higher systolic BP and better cognition.

“For each additional z score weight gain from term to 12 months corrected for prematurity, the total WISC-III score was 1.9 points higher (95% CI, 1.0-2.8); associations of weight gain with WISC-III performance and verbal scales were similar in magnitude and direction,” the researchers wrote.

They also reported that, after adjusting for the same covariates, the odds of having a normal score were 50% higher per additional z score weight gain from term to 12 months (adjusted OR=1.50) when compared with having a low WISC-III total score.

Systolic BP also increased modestly by 0.7 mm Hg per z score weight gain (95% CI, 0.1-1.3), although the adjusted OR was 1.02 (95% CI, 0.78-1.33).

“We found that in preterm infants, more rapid weight gain from term to age 12 months was associated with moderately better cognition, as well as slightly higher BP,” the researchers wrote. “Increased nutritional support for preterm infants after NICU discharge might benefit long-term neurodevelopmental outcomes with only a small effect on BP-related health.”

Belfort MB. Pediatrics. 2010;125:e1419-e1426.

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