Estrous Cycle Ratio as a Reproductive Index in the Rats| Biomed Grid

Estrous cycle is an endogenous rhythm. Previously, studies have evaluated and analyzed the cycle based on its regularity and length and diestrus proportion. The aim of the review is to introduce estrous cycle ratio as a reproductive index and highlight its relevance. Twenty murine studies were retrieved from electronic databases published between 1999 and 2019. Estrous cycle ratio was calculated according to the method of [1]. The result shows that the average estrous cycle ratio is 0.81 with a nadir of 0.5 and a zenith of 1.5. Increase in estrous cycle ratio may signify prolongation of follicular phase length and delay in ovulation. Decrease in estrous cycle ratio may indicate delay in luteal regression with attendant delay in the initiation of new folliculogenesis. Therefore, estrous cycle ratio is an estrous cycle evaluation index.