Birth Weight Effects

Born Too Small: The Effect of Low Birth Weight on Childhood Health and Development

Abstract

Research consistently shows a strong association between birth weight, adjusted for gestational age, and a wide range of childhood and adult outcomes. Prior studies using sibling and twin fixed-effects (FE) designs have helped isolate the causal impact of birth weight, highlighting the potential benefits of reducing the incidence of low birth weight (LBW). However, while these studies have examined the effects of birth weight on outcomes immediately after birth and in adulthood, research tracing the full developmental pathway between these stages remains limited. Although the relationship between birth weight and test scores has been well documented, much less is known about how birth weight shapes health and development from birth through adolescence.

This paper examines the relationship between birth weight and measures of health and development throughout childhood. We construct two samples linked to birth records, allowing us to observe birth weight and gestational age. The first sample includes medical screening records for nearly all 119,258 children in four regions in the Netherlands (2010-2018). The second sample uses administrative data on the universe of 3,105,103 children born in the Netherlands (2000-2020). It includes information on primary school performance, hospital costs, and judge-imposed youth protection interventions.

This study is the first to link novel Preventive Youth Health Care (PYHC) data from four regions to administrative records. PYHC monitors children’s health and development and provides free services to all children in the Netherlands. Its records contain information on weight, height, speech and language skills, and psychosocial development. PYHC conducts 13 check-ups before age four, and three additional check-ups thereafter, achieving a take-up rate of roughly 90% and an average of 32,097 children per check-up.

To estimate the causal impact of birth weight, we use sibling and twin-FE models with a set of controls. The PYHC sample allows only sibling-FE due to the smaller sample size, whereas the administrative sample includes enough twins to estimate both models.

We find a strong positive association between birth weight and childhood overweight: high-birth-weight children are more likely to be overweight through primary school, with the effect fading by secondary school. In contrast, the negative association between birth weight and underweight is strong and persistent, with LBW children more likely to be underweight from the first four weeks of life through age 14.

LBW children also show delayed language and speech development, being less likely to meet age-appropriate benchmarks at ages 2 and 3 or to achieve sufficient scores on standardized language tests at age 11. Other educational outcomes display a similar pattern, with a strong positive relationship between birth weight and academic performance among siblings and twins. By contrast, we find no significant association between birth weight and SDQ scores from ages 3 to 14. Finally, we find a strong association between birth weight and hospital costs at age 0, which persists in the sibling-FE models to age 10 but not in the twin-FE models.

Overall, the findings highlight the lasting consequences of LBW and underscore the importance of targeted early-life interventions for at-risk children.

Click here for the conference presentation