Objective: To determine whether cognitive performance from infancy to adulthood is affected by being born small for gestational age (SGA), and if this depends on the SGA reference used. Furthermore, to determine SGA's effect while considering the effects of very preterm/very low birthweight (VP/VLBW), socio-economic status (SES) and parent-infant relationship.
Design, setting and population: A total of 414 participants (197 term-born, 217 VP/VLBW) of the Bavarian Longitudinal Study.
Methods: Small for gestational age was classified using neonatal or fetal growth references. SES and the parent-infant relationship were assessed before the infant was 5 months old.
Main outcome measures: Developmental (DQ) and intelligence (IQ) tests assessed cognitive performance on six occasions, from 5 months to 26 years of age.
Results: The fetal reference classified more infants as SGA (<10th centile) than the neonatal reference (n = 138, 33% versus n = 75, 18%). Using linear mixed models, SGA was associated with IQ -8 points lower than appropriate for gestational age, regardless of reference used (95% CI -13.66 to -0.64 and 95% CI -13.75 to -1.98). This difference narrowed minimally into adulthood. Being VP/VLBW was associated with IQ -16 (95% CI -21.01 to -10.04) points lower than term-born participants. Low SES was associated with IQ -14 (95% CI -18.55 to -9.06) points lower than high SES. A poor parent-infant relationship was associated with IQ -10 points lower than those with a good relationship (95% CI -13.91 to -6.47).
Conclusions: Small for gestational age is associated with lower IQ throughout development, independent of VP/VLBW birth, low SES or poor parent-child relationship. Social factors effects on IQ comparable to those of SGA and should be considered for interventions.
Tweetable abstract: Small for gestational age is associated with lower cognitive performance from infancy to adulthood.
Keywords: Cognition; IQ; cognitive development; growth restriction; small for gestational age; term; very preterm.
© 2020 The Authors. BJOG: An International Journal of Obstetrics and Gynaecology published by John Wiley & Sons Ltd on behalf of Royal College of Obstetricians and Gynaecologists.