Vitamin D Levels During Pregnancy and Dental Caries in Offspring.

Importance: Maternal vitamin D level during pregnancy has been repeatedly reported to be associated with early childhood caries (ECCs) in offspring, yet the conclusions remain inconsistent. Objective: To evaluate the association between maternal vitamin D status in different trimesters during pregnancy and offspring dental caries. Design, Setting, and Participants: This prospective cohort study was based on the Zhoushan Pregnant Women Cohort, which enrolled pregnant women between August 2011 to May 2021, and followed up on their offspring until November 2022, at Zhoushan Maternal and Child Health Hospital in Zhoushan, Zhejiang Province, China. Data were analyzed from October 2024 to April 2025. Exposures: Maternal plasma 25-hydroxyvitamin D (25[OH]D) levels measured in the first, second, and third trimesters and vitamin D deficiency (VDD). Main Outcomes and Measures: The primary outcome was offspring ECCs. Secondary outcomes included the decayed, missing, or filled teeth (dmft, with lowercase term denoting primary, instead of permanent, dentition) index and caries rate (the ratio of dmft to number of erupted teeth). Results: The cohort included 4109 mother-offspring pairs (maternal median [IQR] age, 29.0 [27.0-32.0] years; offspring gestational age at birth, 39.0 [38.0-40.0] weeks; 2121 males [51.6%]), of whom 960 children had ECCs and 3149 did not. Higher maternal 25(OH)D levels were associated with reduced odds of ECCs in offspring (first trimester odds ratio [OR], 0.98 [95% CI, 0.97-0.99], false discovery rate [FDR]-adjusted P = .009; second trimester OR, 0.98 [95% CI, 0.97-0.99], FDR-adjusted P = .001; third trimester OR, 0.99 [95% CI, 0.98-1.00], FDR-adjusted P = .009), while Cox proportional hazards regression models showed protective benefits of 25(OH)D levels against ECC risk throughout all trimesters. Categorical analyses suggested elevated odds of ECCs in offspring of mothers with vitamin D insufficiency, VDD, or severe VDD compared with the vitamin D sufficiency group, although the statistical significance of some associations was attenuated after FDR correction. Moreover, higher maternal 25(OH)D levels (μg/mL) were associated with lower dmft scores (third trimester: β [SE] = -9.97 [3.97]; P = .01) and caries rate (third trimester: β [SE] = -50.87 [19.78]; P = .01). Generalized estimation equation models also confirmed the inverse associations. Conclusions and Relevance: In this cohort study, maternal 25(OH)D levels throughout pregnancy were inversely associated with odds of offspring ECCs. These findings support the potential benefit of vitamin D supplementation before or during pregnancy in reducing the risk and severity of childhood dental caries.