Vitamin D2026-06

Prevalence and Seasonal Variation in Serum 25-Hydroxyvitamin D Concentrations Among Women of Reproductive Age.

Guo Hong-Xia, Zhang Zhi-Hui, Ren Hong-Wei, Wang Hui-Yu — Clinical laboratory

Summary

A study in China found that most women of reproductive age had very low vitamin D levels, with over 90% being deficient. Vitamin D levels were higher in older women (35 and above) and varied significantly with the seasons, peaking in summer and dropping in spring. This highlights a widespread need for better vitamin D strategies for women planning pregnancy.

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Key points

Most women of reproductive age in this study had insufficient or deficient vitamin D levels.
Vitamin D levels were generally higher in women aged 35 and older compared to younger women.
Seasonal changes significantly affected vitamin D levels, with the highest levels in summer and the lowest in spring.
The findings suggest a need for routine vitamin D assessment for women planning pregnancy.

What the study looked at

What question the study asked: Researchers wanted to understand the vitamin D status of women in their childbearing years and how their levels might differ based on age and the time of year. This information is crucial for developing health strategies related to vitamin D. How it was studied: The study looked back at health examination data from over 2,300 women of reproductive age in Beijing, China, who had preconception check-ups between late 2022 and late 2024. Participants were grouped by age (under 35 vs. 35 and older) and by the season their blood sample was taken. What it found: The study revealed a very high rate of low vitamin D levels, with over 90% of women being deficient. Women aged 35 and older generally had higher vitamin D levels than younger women. Additionally, vitamin D levels showed clear seasonal patterns, being highest in summer and autumn and lowest during winter and spring.

Dietary takeaway

Given the high prevalence of low vitamin D levels, women of reproductive age, especially those planning pregnancy, might consider discussing their vitamin D status with a healthcare provider. Incorporating vitamin D-rich foods like fatty fish, fortified dairy, and certain mushrooms into your diet, and getting safe sun exposure when possible, can help. Remember, this is one study, and individual needs can vary, so personalized advice is always best.

Abstract

BACKGROUND: This study aimed to investigate serum 25-hydroxyvitamin D [25(OH)D] concentrations among women of reproductive age, stratified by age and season, in order to provide information for vitamin D-related health strategies for this population. METHODS: A retrospective analysis was conducted on serum 25(OH)D concentrations in women of reproductive age who underwent preconception health examinations at the Physical Examination Department of Haidian District Maternal and Child Health Care Hospital between December 2022 and December 2024. Participants were stratified by age into two groups: advanced maternal age (≥ 35 years) and typical maternal age (< 35 years). Seasonal categorization included spring, summer, autumn, and winter. Intergroup comparisons were performed, and vitamin D nutritional status was classified based on established thresholds. RESULTS: A total of 2,325 women were included in the study. The mean serum 25(OH)D concentration was 34.45 ± 11.07 nmol/L. Vitamin D deficiency was observed in 92.47% of participants, insufficiency in 6.24%, and sufficiency in only 1.29%. Participants in the advanced maternal age group demonstrated significantly higher serum 25(OH)D concentrations compared to those in the normal maternal age group (p < 0.05). Seasonal variation in serum 25(OH)D concentrations was observed, with the highest levels recorded during summer and the lowest in spring. Concentrations in summer and autumn were significantly higher than those in winter and spring (p < 0.05); however, no significant differences were found between summer and autumn or between winter and spring (p > 0.05). CONCLUSIONS: A high prevalence of vitamin D deficiency was observed among women of reproductive age in Haidian District, Beijing, with significant variations by age and season. Routine assessment of serum 25(OH)D concentrations is recommended for women planning pregnancy to facilitate timely and appropriate vitamin D supplementation strategies.

View on PubMed →DOI: 10.7754/Clin.Lab.2025.250606