More Rapid Weight Gain by Age 1 Year May Improve Neurodevelopment of Preterm Infants

Laurie Barclay, MD & Désirée Lie, MD, MSEd
From MedscapeCME Clinical Briefs

May 25, 2010 — In preterm infants, more rapid weight gain in the first year of life is associated with modest neurodevelopmental advantages and only small blood pressure (BP)–related effects at school age, according to the results of a study reported online May 17 in Pediatrics.

"More rapid infant weight gain may have benefits, such as to neurodevelopment, as well as risks, such as higher BP," write Mandy B. Belfort, MD, MPH, from Children's Hospital Boston in Boston, Massachusetts, and colleagues. "The balance of risks and benefits of rapid infant weight gain for preterm infants is poorly understood."

The goal of the study was to evaluate the association of infant weight gain with systolic BP (SBP) and IQ at school age in former preterm, low-birth-weight infants. In the Infant Health and Development Program, an 8-center longitudinal study, 911 children born at 37 weeks' gestation or less and weighing 2500 g or less were weighed at term and at 4 and 12 months' corrected ages.

Blood pressure was measured 3 times at 6.5 years, and the Wechsler Intelligence Scale for Children, Third Edition (WISC-III) was administered at 8 years to test IQ. The exposure "infant weight gain" was modeled in linear regression as the 12-month weight z score adjusted for the term weight z score.

At 12 months, median weight z score was –0.7 (interquartile range, –1.5 to –0.0). At 6.5 years, mean SBP was 104.2 ± 8.4 mm Hg, and at 8 years, mean WISC-III total score was 91 ± 18. For each z score additional weight gain from term to 12 months, SBP was 0.7 mm Hg higher, and WISC-III total score was 1.9 points higher, after adjustment for child age, sex, and race and maternal education, income, age, IQ, and smoking.

"In preterm infants, there seem to be modest neurodevelopmental advantages of more rapid weight gain in the first year of life and only small BP-related effects," the study authors write.

Limitations of this study include birth of the cohort in the 1980s, when neonatal intensive care unit practices differed from current practices; and lower socioeconomic status of mothers of the infants in this cohort, possibly limiting generalizability.

"Increased nutritional support for preterm infants after NICU [neonatal intensive care unit] discharge might benefit long-term neurodevelopmental outcomes, with only a small effect on BP-related health," the study authors conclude. "Although small IQ differences are not clinically significant for individuals, shifting the IQ curve of a population upward by a few points can have an important impact."

The National Institutes of Health, the Robert Wood Johnson Foundation, Maternal and Child Health Bureau, and Pew Charitable Trust supported this study. The study authors have disclosed no relevant financial relationships.

Pediatrics. Published online May 17, 2010. Abstract

Clinical Context

Approximately 12.7% of all births in the United States in 2005 were preterm, and there is an increasing burden of neurodevelopmental problems among preterm infants. Although infant weight gain has been associated with a reduced risk for low IQ among preterm infants, it is unclear if greater weight gain in infancy is associated with adverse metabolic factors such as BP.

This is a longitudinal cohort study of preterm infants at 8 US centers to examine the association between weight gain between birth and 12 months and SBP at age 6.5 years and IQ at age 8 years.
•Greater weight gain in the first year for preterm low-birth-weight infants is associated with a small increase in SBP (0.7 mm Hg) at age 6.5 years.
•Greater weight gain in the first year for preterm low-birth-weight infants is associated with a significant increase in IQ at age 8 years