To check the thickness of the endometrium, it is best to have a vaginal ultrasound 3 days after menstruation to find out how thick the endometrium is. the thickness of the endometrium varies at different times of the menstrual cycle, for example, about 3 days after menstruation, the thickness of the endometrium is 0.6cm-0.7cm. if the endometrium thickens further during ovulation, it should reach 1.0 cm, the endometrium should be above 0.9 cm at the time of ovulation for a fertilized egg to be able to implant. The thickness of the endometrium increases as it enters the secretory phase, reaching 1.0 cm-1.2 cm before menstruation.