Researchers in Italy looked at the success rates of assisted fertility procedures in 154 women who were deficient in the vitamin and 181 with sufficient levels in their blood. The second group was nearly twice as likely to conceive as the first.
A "sufficient" amount of vitamin D was defined as at least 20 nanograms (ng) per millilitre of blood - less than the recommended level of 30 ng, said the researchers.
Study author Dr Alessio Paffoni, from the Maggiore Policlinico Hospital in Milan, said: "We found that women who had sufficient levels of vitamin D were more likely to produce high-quality embryos and more likely to become pregnant than women who were deficient in vitamin D."
Dr Paffoni added: "Although randomised clinical trials are needed to confirm the findings, our results certainly suggest that low levels of vitamin D contribute to infertility."