Short answer: Observational studies have found a link between vitamin D deficiency and IVF outcomes. This does not show that extra vitamin D improves fertility in those who already have sufficient levels. The need for supplements is determined by factors including diet and sun exposure, not solely by the fact that you are planning a pregnancy.
Why might vitamin D affect fertility?
Vitamin D receptors are found in several reproductive tissues in both women and men, including the ovaries and the lining of the uterus. This makes it biologically plausible that vitamin D status could affect ovarian function, embryo quality, and uterine receptivity.
What does the research say?
A systematic review and meta-analysis of women undergoing assisted reproduction found that those with vitamin D deficiency had a lower chance of a live birth on average than those with sufficient levels. At the same time, it is still unclear whether a vitamin D supplement itself improves IVF outcomes—more and larger studies are needed in this area. Nevertheless, avoiding deficiency appears to be a reasonable approach.
Who may need supplements?
Fatty fish and fortified foods provide vitamin D. The Swedish Food Agency's supplement recommendations apply to specific risk groups, such as people with very limited sun exposure or low intake from food. Pregnant women are covered by the same basic principles as other adults.
General information, not medical advice. Ask a healthcare professional if you need an assessment or supplements.
Sources
- Chu J, et al. (2018). Vitamin D and assisted reproductive treatment outcome: a systematic review and meta-analysis. Human Reproduction.
- Swedish Food Agency: advice for pregnant women