A decade-long assessment reveals persistent vitamin D deficiency and its associated factors in early-pregnant women from northern China (2016–2025)

Abstract

Background Large-scale data on vitamin D status in early-pregnant women in high-risk Northern China are scarce. This study evaluated the decadal trends (2016–2025) and associated factors of serum 25(OH)D levels in this population in Shanxi Province. Methods This retrospective cohort included 20,693 early-pregnant women (<14 weeks). Serum 25(OH)D was measured. Logistic regression assessed associations with of season, age, conception mode, and the COVID-19 period. Results The median 25(OH)D was 36.12 nmol/L, indicating a concerning status. Season was the strongest associated factor. The pandemic period (2020–2022) saw a significant rise in severe deficiency (<30 nmol/L) to 35.6%. Advanced maternal age (≥35) and ART conception were linked to higher levels. Summer and autumn were protective factors for sufficiency, while natural conception was an associated factor for deficiency. Conclusion Severe vitamin D deficiency is widespread. Findings advocate for routine perinatal vitamin D screening and supplementation, with tailored strategies for winter and specific subgroups.