Follicles and their size and status are a vital part of a womans fertility and are an important factor during fertility treatments. When the follicle has grown to the right size, it releases an egg ready to be fertilized. When the follicle reaches close to its maximum size, it releases even more estrogen. While before, increased levels of estrogen led to decreasing levels of fsh, when the estrogen levels are exceptionally high, there is a switch in how the pituitary gland reacts to the hormone. Objectiveto identify follicle sizes on the day of trigger most likely to yield a mature oocyte following hcg, gnrh agonist (gnrha), or kisspeptin during ivf treatment. Designretrospective analysis to determine the size of follicles on day of trigger contributing most to the number of mature oocytes retrieved using generalized linear regression and random forest models applied to data from ivf. In a natural (unstimulated cycle) or clomiphene citrate cycle, mature follicle size is between 18 - 30 mm. If triggered, these cycles are typically triggered when follicle size is between 17-26mm (dependent of the practice and ivf lab). In a gonadotropin cycle, mature follicle size is between 16 - 20 mm. When the time comes, and the follicle has grown to the right size, it ruptures and releases a matured egg ready to be fertilised. A common misconception is that each follicle releases multiple eggs. However, as to the question of how many eggs are in a follicle, the answer is just one. An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries. It secretes hormones that influence stages of the menstrual cycle. Women begin puberty with about 400,000 follicles, each with the potential to release an egg cell (ovum) at ovulation for fertilization.