The influence of fetal growth reference standards on assessment of cognitive and academic outcomes of very preterm children

Objective: To compare 3 methods of identifying small-for-gestational-age (SGA) status in very preterm children as related to cognitive function and academic outcome.

Study design: There were 1038 singletons in the Epipage Study, born before 33 weeks in 1997 without severe neurosensory impairment, who were classified as SGA when birth weight was below the 10th percentile according to: (1) birth weight (bw) reference: SGA(bw)/appropriate for gestational age (AGA)(bw); (2) intrauterine (intraut) reference: SGA(intraut)/AGA(intraut); and (3) intrauterine reference customized (cust) according to individual characteristics: SGA(cust)/AGA(cust). Cognitive function was assessed by the mental processing composite (MPC) score of the Kaufman Assessment Battery for Children at age 5 and academic achievement by a parental questionnaire at age 8.

Results: Of the children, 15% were SGA(bw), 38% were SGA(intraut), and 39% were SGA(cust). All children SGA(bw) were also SGA(intraut) and SGA(cust). MPC was <85 in 32% of children and 27% had low academic achievement. AGA(bw)/SGA(intraut) children had a significantly increased risk of MPC <85 (adjusted OR 1.74, 95% CI 1.22-2.28) or low academic achievement (adjusted OR 1.64, 95% CI 1.05-2.55) compared with AGA(bw)/AGA(intraut) children. The SGA(cust) group was only slightly different from the SGA(intraut) group.

Conclusions: An intrauterine reference identified very preterm infants at risk of poor cognitive or academic outcomes better than a birth weight reference. Customization resulted in only slight modifications of the SGA group.