Vitamin A, D, and E Levels and Reference Ranges for Pregnant Women: A Cross-Sectional Study 2017-2019

Background: Pregnancy-specific vitamin reference ranges are currently not available for maternal vitamin management during pregnancy. This study aimed to propose pregnancy-specific vitamin reference ranges and to investigate the factors influencing vitamin levels during pregnancy. Methods: A cross-sectional study that included pregnant women from 17 cities in 4 provinces in western China was conducted from 2017 to 2019. A total of 119,286 subjects were enrolled in the study. Serum vitamin A, vitamin D, and vitamin E levels were measured. A multivariable linear regression model and restricted cubic spline function were used to analyze the factors related to vitamin levels. Results: The reference ranges for vitamin A, D, and E levels were 0.22-0.62 mg/L, 5-43 ng/mL, and 7.4-23.5 mg/L, respectively. A linear relationship was found between vitamin E level and age (β = 0.004; 95% confidence interval [CI], 0.0037-0.0042; p < 0.001), and a nonlinear relationship was found between vitamin D (p nonlinear = 0.033) and vitamin A levels and age (p nonlinear < 0.001). Season, gestational trimester, and regions were related to the levels of the three vitamins in the multivariable models (p < 0.05). Conclusions: The lower limit of vitamin A during pregnancy was the same as the reference value currently used for the general population. The reference ranges of vitamins D and E during pregnancy were lower and higher, respectively, than the currently used criteria for the general population. Vitamin A, D, and E levels differed according to age, season, gestational trimester, and region.