The endometrial lining 0.3cm is not necessarily harmful, it should mainly depend on the stage of the menstrual cycle that the examination time is in. If the period has just ended not long ago, the endometrial lining 0.3cm should be normal, if the endometrial lining is 0.3cm around the time of ovulation, the endometrial lining is considered thin, the main harm may affect pregnancy and may lead to infertility, the specific need to find the cause and give the appropriate treatment. If it is determined that the endometrium is thin, it is seen that the endometrium is damaged due to multiple inductions or miscarriages, or it may be due to poor ovarian function and low levels of estrogen and progesterone secretion, which do not promote the endometrial growth well.