The thickness of the lining of the uterus varies with the menstrual cycle, and the lining of the uterus itself thickens when you are pregnant or approaching menstruation. If the lining of the uterus is thin, it may affect the fertilization of the fertilized egg, leading to miscarriage with an early onset or biochemical pregnancy, spontaneous abortion, and so on. If the endometrium is slightly thicker, it will not affect the implantation of the fertilized egg. Of course, if the endometrium is particularly thick, it may also affect the implantation of the fertilized egg, resulting in a biochemical pregnancy, and the patient is advised not to be overly nervous. Generally speaking, after pregnancy, the level of estrogen in the body decreases, the level of progesterone increases, and the endometrium develops into a condition suitable for the fertilization of the egg, which is a normal physiological phenomenon for the protection of pregnancy. Early pregnancy can also check the ultrasound to see the condition of the uterine lining, to determine whether the fertilized egg has been bedded to rule out ectopic pregnancy.