The thickness of the endometrium is 5mm, which cannot be said to be abnormal, but only in which period. If it is 5mm in the secretory phase, or early in the proliferative phase, it is also a normal phenomenon. If it reaches 5mm before menstruation, it should still belong to a thin endometrial state. Because the thickness of the endometrium is usually between 8-13mm, it is normal to reach this thickness before the start of the menstrual cycle. If it is 5mm at this period, it should still be relatively thin. If you have a desire to get pregnant, it is advisable to have a further examination to see what the specific cause of the thin endometrium is and to carry out symptomatic treatment so as not to delay having children, as well as to have a worse situation in the future.