<prompt> Which of the following method is the best predictor for ovulation in a female infertility patient during a menstrual cycleBasal body temperatureHormonal StudyEndometrial biopsyFern study  <response>: In the anovulatory cycle, plasma progesterone reaches a peak of 15ngml at mid-luteal phase 22-23days.Basal body temperature BBT falls at the time of ovulation by about 12degree. During the progestational half of cycle, the temperature is slightly raised above the preovulatory level. But it is now obsolete because:Tedious daily recordingNot very accurateBetter modalities are availableIn endometrial biopsy endometrium from the uterus is curetted preferably 1 or 2days prior to the onset of menstruation. Histological examination done for secreatory changes. Now a days endometrial biopsy is omitted as a routine investigation of infertility. Only used in suspected tubercular endometritisFern test: cervical mucus is examined under a low power microscope. During estrogenic phase, it shows a charecteristic fern patten which disappears after ovulation 