The exact reasons are not known, but it is likely to be the result of several processes. The leading explanations are hemodilution[1] due to the increase in blood volume during pregnancy, decreased exposure to the sun, and the fetal demand for vitamin D, because it is an essential nutrient.
Why is vitamin D often lower in pregnant individuals?
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•Last Updated: May 16, 2025
Vitamin D levels are often lower in pregnant individuals due to factors such as hemodilution from increased blood volume, reduced sun exposure, and the nutritional demands of the developing fetus. The exact reasons remain unclear, but these processes are considered the leading explanations.