The relationship between health status at birth and short-term health has been established; however, the relationship with long-term health remains unclear, particularly in Japan. This study investigates the effect of birth weight on child development using data from the Longitudinal Survey of Newborns in the twenty-firstst Century—a nationwide birth cohort study conducted by the Ministry of Health, Labour and Welfare. We employ twin fixed-effects estimation to examine the effects of birth weight on physical development, using measures including weight, height, percentage of overweight indexes, and hospitalization, with a focus on how the effects vary with age up to 12 years. The results show that for all ages, lower birth weight negatively affects body size but does not affect probability of hospitalization or overweight/underweight status, indicating a limited impact. However, lower birth weight shows larger adverse effects on body size and the probability of hospitalization when the sample is limited to birth weight < 2300 g compared with the full sample, suggesting the importance of considering heterogeneity. Japanese public policy for perinatal care may have contributed to this limited impact of birth weight. Additional care aimed at preventing low birth weight and greater focus on smaller babies would be more beneficial.

已经确定了出生时健康状况与短期健康之间的关系；但是，与长期健康的关系仍然不清楚，尤其是在日本。本研究使用二十一世纪新生儿纵向调查的数据调查了出生体重对儿童发育的影响，这是由厚生劳动省进行的全国性出生队列研究。我们采用双胞胎固定效应估算方法，使用体重，身高，超重指数百分比和住院治疗等指标来检查出生体重对身体发育的影响，重点是影响随年龄增长至12岁的变化。结果表明，对于所有年龄段，较低的出生体重都会对体重产生负面影响，但不会影响住院或超重/体重不足状态的可能性，表明影响有限。但是，与全部样本相比，当样本的出生体重限制在2300 g以下时，较低的出生体重对人体尺寸和住院几率显示出更大的不利影响，这表明考虑异质性的重要性。日本的围产期保健公共政策可能是造成出生体重影响有限的原因。旨在防止低出生体重和更多地关注较小的婴儿的额外护理会更加有益。日本的围产期保健公共政策可能是造成出生体重影响有限的原因。旨在防止低出生体重和更多地关注较小的婴儿的额外护理会更加有益。日本的围产期保健公共政策可能是造成出生体重影响有限的原因。旨在防止低出生体重和更多地关注较小的婴儿的额外护理会更加有益。