Is low temperature of the follicular fluid prior to ovulation necessary for normal oocyte development?

Because low temperature in the testis is essential to normal spermatogenesis, we speculated whether a low follicular temperature could also be of importance for the oocytes as they resume meiosis at ovulation. We measured the temperature of the follicular fluid and of the ovarian stroma in 26 follicles in 14 women. In 25 follicles (13 women) the follicular fluid was colder than the ovarian stroma. This temperature difference increases toward ovulation (maximum, 2.3 degrees C). In one case, the measurements of the follicular/stromal temperature difference showed an inverse pattern, the follicular fluid being 0.2 degree C warmer than the stroma. This woman was infertile, and oocyte evaluation for in vitro fertilization had five times shown the oocytes unable to divide in culture. The present study supports the idea that low temperature of the follicular fluid prior to ovulation may be essential for normal oocyte development.