Neuro-developmental outcome of a large cohort of growth discordant twins

Our aims were to study the effect of birthweight growth discordance (≥20%) on neuro-developmental outcome of monochorionic and dichorionic twins and to compare the relative effects of foetal growth discordance and prematurity on cognitive outcome. We performed a cross-sectional multicentre prospective follow-up study from a cohort of 948 twin pregnancies. One hundred nineteen birthweight-discordant twin pairs were examined (24 monochorionic pairs) and were matched for gestational age at delivery with 111 concordant control pairs. Participants were assessed with the Bayley Scales between 24 and 42 months of age. Analysis was by paired t test for intra-twin pair differences and by multiple linear regression. Compared to the larger twin of a discordant pair, the smaller twin performed significantly worse in cognition (mean composite cognitive score difference = -1.7, 95% confidence interval (CI) = 0.3-3.1, p = 0.01) and also in language and motor skills. Prematurity prior to 33 weeks' gestation, however, had a far greater impact on cognitive outcomes (mean cognitive composite score difference = -5.8, 95% CI = 1.2-10.5, p = 0.008).

Birthweight growth discordance of ≥20% confers an independent adverse effect on long-term neuro-development of the smaller twin. However, prior to 33 weeks' gestation, gestational age at birth adversely affects cognitive development to a greater extent than foetal growth discordance.