[pronut-hiv] Improved Fetal Growth May Predict Increased IQ at School Age

["ProNut-HIV" <pronut-hiv@healthnet..org>]

June 24, 2009 â Improved fetal growth within the normal birth size range is linked to higher IQ scores in Asian children, according to the results of a study reported in the June issue of Pediatrics.

"Studies on (very) low [birth weight (BW)] and premature children showed that IQ is consistently correlated to BW," write Birit F.P. Broekman, MD, MA, from the National University of Singapore/National University Health System, Singapore, and colleagues. âIn the normal birth size range, this association is less conclusive."

The goal of the study was to evaluate the associations between birth length, birth weight, head circumference, and gestational age within the normal birth size range and childhood IQ in Asian children.

The study cohort consisted of 1979 (68%) of 2913 Asian children aged 7 to 9 years who were recruited from 3 schools in Singapore and evaluated every year beginning in 1999. Health personnel recorded birth parameters and childhood IQ at ages 8 to 12 years, as measured with the Raven's Standard Progressive Matrices.

For the group of 1645 children who had IQ testing, the mean IQ score was 114.2. For every 1-centimeter increase in birth length, 1 kg in birth weight, or 1 centimeter in head circumference, there was a corresponding increase in IQ of 0.49 points (P for trend < .001), 2.19 points (P for trend = .007), and 0.62 points (P for trend = .003), respectively, after adjustment for multiple confounders. Exclusion of premature children and children with extreme weights and head circumferences did not abolish these associations.

"Longer birth length, higher birth weight, or larger head circumferences within the normal birth size range are associated with higher IQ scores in Asian children," the study authors write. "Our results suggest that antenatal factors reflected in altered rates of growth but within the normative range of pregnancy experiences play a role in generating cognitive potential. This has implications for targeting early intervention and preventative programs."

Limitations of this study include possible selection biases caused by loss to follow-up, missing birth-parameter data, and demographic differences between included and excluded children.

"Future studies in normal birth sized children are needed to explore the connections between variations in fetal growth, brain development, and the potential influence of gene environmental interactions," the study authors conclude.

The National Medical Research Council, Singapore, supported this study. The study authors have disclosed no relevant financial relationships. 

Pediatrics. 2009;123:e1011-e1016.