Melatonin is a very small molecule whose effects can be both detrimental and beneficial to the ovaries depending on its concentration. Too much of anything is usually not good and so is the case with melatonin. Very high doses can be damaging, but in the right amount melatonin may be able to combat various diseases and increase the chances for fertility in women.
Starr, J. (2011). The Effect of Melatonin on the Ovaries. The Science Journal of the Lander College of Arts and Sciences, 5 (1). Retrieved from https://touroscholar.touro.edu/cgi/viewcontent.cgi?article=1138&context=sjlcas