Effect of freezing and cryostorage on follicular fluid vitamin D levels

Lay summary: In the studies assessing the relationship between vitamin D levels and pregnancy outcomes in in vitro fertilization, doctors sometimes collected and froze the follicular fluid (fluid around eggs in a woman's ovaries) so they can test it later for research. This study aimed to find out if freezing and storage changes the level of vitamin D in that fluid, which could affect how reliable the tests are. We collected follicular fluid of 20 women going through in vitro fertilization. The samples were split into portions and were frozen at two different temperatures: -20 and -80°C. Vitamin D levels were analysed at baseline (before freezing), after 2 weeks and again after 7 months. The results showed that freezing and storage did not make a noticeable difference in vitamin D levels. That means storing the fluid this way for up to 7 months is an acceptable method for research.