Does Catch-Up Growth Come with a Cognitive Cost? Cognitive Outcome and Growth Patterns in Growth Discordant Identical Twins.

Abstract

To determine whether it is the magnitude of early postnatal catch-up growth (CUG) in response to fetal growth restriction (FGR) or the FGR itself that negatively impacts cognitive outcome in a model of monochorionic twins discordant for fetal growth. This analysis is part of the LEMON study, a cohort study including all monochorionic twins with selective FGR aged 3 through 17 years. Growth measurements as documented by our primary care system were collected retrospectively. An age-appropriate neurodevelopmental test was performed generating a full-scale IQ (FSIQ). CUG at 2 years was calculated as (weight [kg] at 2 years-birth weight [kg]). We used a multivariable regression model investigating the association between FSIQ (outcome) and birth weight zscore, gestational age at birth and CUG at 2 years (predictors). Generalized estimating equations accounted for the fact that observations between cotwins are not independent. Median age at follow-up of the 46 included twin pairs was 11 (IQR 8-13) years. Birth weight z score and gestational age at birth were significantly associated with FSIQ, with β-coefficients of 5.897 (95% CI 3.382-8.411), and 2.589 (95% CI 1.227-3.951), respectively (P < .0001). Adjusted for birth weight z score and gestational age, CUG in the first 2 years after birth was not significantly associated with FSIQ (β-coefficient 0.108 [95% CI -1.373 to 1.590], P = .886). Our results, combining detailed growth measurements and neurodevelopmental follow-up in a discordant identical twin model, demonstrate that FGR itself rather than early postnatal CUG has negative consequences for cognitive development.