It is possible to measure the thickness of the lining during ovulation. The endometrium is composed of a functional layer and a basal layer, and its thickness changes cyclically with changes in estrogen and progesterone. Usually, the endometrium is detected by ultrasound, and the normal value of endometrial thickness during ovulation is 1.0 to 1.2 centimeters. The thickness of the uterine lining and the development of the follicles can be monitored under ultrasound to estimate the time of the onset of menstruation. Ultrasound can be used to detect the thickness of the lining of the uterus before the onset of menstruation. Ultrasound is radiation-free, so there is no need to worry too much about the impact on your health. Meanwhile, before the test, it is best not to eat spicy and stimulating things, avoid staying up all night, and keep your mood relaxed and happy. Consult your physician for advice.