The equity and effectiveness of China's 2009 folic acid supplementation programme for long-term child development

Maternal folic acid supplementation is a cornerstone of public health for preventing neural tube defects (NTDs), yet its long-term impact on child development remains underexplored.

This study evaluates the long-term cognitive and mental health associations of maternal folic acid supplementation by utilising China's 2009 Folic Acid Supplementation Programme for rural women as a quasi-experimental framework.

We analysed 1,953 children aged 10-15 years from the 2020 China Family Panel Studies. Using provincial NTD prevalence in 2009 from the Maternal and Child Health Surveillance system as a proxy for intervention intensity, we employed difference-in-differences models to estimate associations, adjusting for demographic and parental covariates.

Maternal folic acid supplementation was significantly associated with improved outcomes among girls: higher memory scores ($\beta$ [95% CI], 0.232 [0.069, 0.394]), enhanced numerical reasoning skills (5.234, [2.188, 8.279]), lower Center for Epidemiological Studies Depression Scale score (-0.523 [-0.933, -0.113]), and reduced likelihood of depressive symptoms (-0.024 [-0.048, -0.001]). No comparable associations were observed in the boys. Although cognitive associations were observed across socioeconomic status (SES) groups among girls, the mental health associations were concentrated among girls from higher-SES families. Results were robust to adjustment for covariates.

This study highlights sex-specific, long-term associations of maternal folic acid supplementation but reveals that socioeconomic disparities may constrain mental health gains. Thus, universal nutrition interventions alone may be insufficient to bridge health equity gaps. The findings should be interpreted within the broader nutritional ecology and alongside concurrent macro-social changes that shape child development outcomes.