The earliest morphological evidence of ovulation on endometrial biopsy is:

Endometrial biopsy was used in the past to find out whether the female has ovulated or not. Nowadays USG follicular monitoring is being done Subnuclear basal vacuolation is characterized by glandular growth and presence of vacuoles due to secretion of glycogen between nuclei and basement membrane. It is due to the effect of progesterone. Basal vacuolization is the earliest evidence of ovulation (36-48 hours after ovulation) and persists until the about 21st day of the cycle. Pseudostratification of nuclei is characteristic of proliferation phase but persists until active progesterone secretion begins. Hence, it is noted until the 18th 19th day of the menstrual cycle.