Early birth is a key factor in educational disadvantage of twins: A data linkage study

Abstract

Aim To assess educational outcomes of twins and quantify the degree this is mediated by gestational age and other perinatal factors. Methods We conducted a population‐based record‐linkage cohort study of all live births ≥24 weeks gestation in New South Wales, Australia with a corresponding standardised school test result for grade 3 in 2008‐2014. The primary outcome was whether a child met the National Minimum Standard (NMS) cut‐off in literacy and numeracy domains. Robust multivariable Poisson models were used to obtain adjusted relative risks (aRRs), and mediation analysis conducted to assess contributing factors on the causal pathway. Results Of 351 791 liveborn infants, 10 365 (2.9%) were twins. After adjusting for maternal covariates and compared with singletons, twins had an increased risk of not meeting the NMS for all five literacy and numeracy domains (aRR 1.27‐1.45, P < .001). Gestational age alone mediated up to 73% of aRRs and small for gestational age further attenuated these effects with only minimal risk remaining after adjusting for all mediators (aRR 0.94‐1.07). Conclusion Almost all of the educational disadvantage experienced by twins, compared with singletons, is attributable to the risk associated with shorter gestational age, and partly by poor foetal growth. These findings support efforts to prolong gestation of twin pregnancies.

Justifying Separate Experiences for Twins: Dorothy Burlingham’s Classic Twin Study/Twin Research Reviews: Monozygotic Twins with Maturity-Onset Diabetes, Gene Editing of Chinese Twins, Educational Disadvantage of Early-Born Twins and Developmental Trajectories of Movements in Fetal Twins/In the News: Twins with Nearly Identical License Plates, Rare Case of Fetus-in-Fetu, Twin Brothers Killed at Pearl Harbor, Death of a 96-Year-Old Twin Holocaust Survivor, Death of Male–Female Twin Toddlers in a Heated Car

“…Researchers in Australia pointed out that twins are at greater risk for poor neurodevelopmental outcomes than nontwins (Zeltzer et al, 2019). They were specifically interested in knowing whether these deficits are tied to twin-specific factors or other risk factors, such as shorter gestational age and small size for gestational age.…”

To be born twin: effects on long-term neurodevelopment of very preterm infants—a cohort study

“…It remains unclear whether twin pregnancy itself is associated with an increased likelihood of adverse neurodevelopmental outcomes or if this effect is related to twin-induced prematurity. Notably, the disadvantages experienced by twins are mainly attributable to the risk associated with shorter gestational age and poor foetal growth ( 18 ). Recent studies ( 19 , 20 ) have compared the neurodevelopmental outcomes of preterm multiples and preterm singletons and found no differences at a general level while a slightly lower mean score was observed for the locomotor and personal-social subscales ( 19 ) and for the verbal intelligence quotient ( 20 ).…”

Highlights in this issue

“…Most of the educational disadvantages experienced by a cohort of twins, compared with singletons, were due to shorter gestational age, and it was also partly associated with poor foetal growth. These findings from an Australian data linkage study have prompted the authors to support efforts to prolong the gestation of twin pregnancies 5. …”