Trends, disparities, and socioeconomic inequalities in periconceptional folic acid supplementation in China: a nationwide survey analysis.

Periconceptional folic acid supplementation (FAS) is known to reduce the risk of adverse pregnancy outcomes, but limited evidence exists on its national coverage and socioeconomic disparities in China. This study used data from a nationwide survey of over 11 million reproductive-aged couples between 2012 and 2019 to examine patterns, trends, and inequalities in overall and adequate FAS use. Modified Poisson regression models were used to estimate the associations between parental separate and joint SES indicators and periconceptional FAS use. Socioeconomic inequalities were quantified using the Erreygers Concentration Index based on maternal education. Overall FAS use increased from 2012 to 2019 to reach 92.6% (95% CI 89.8%-95.5%) in urban and 92.1% (95% CI 90.4%-93.8%) in rural areas. Despite this increase, adequate adherence remained suboptimal at 64.8% (95% CI 59.9%-69.6%) for urban and 66.0% (95% CI 61.2%-70.8%) for rural participants. Lower maternal SES was strongly associated with reduced FAS use. Decomposition analysis established maternal education as the primary driver of inequality and accounted for the largest disparity in adequate use. Although maternal factors mediated the influence of paternal education on overall use, low paternal education persisted as an independent barrier to adequate adherence. Our study confirms a relatively low rate of adequate periconceptional FAS use. Prevention efforts should target high-risk groups by addressing specific risk factors and broader determinants of health.