The endometrial lining of 14mm is relatively thick and the fertilized egg is less likely to implant, but some do implant and end up with a healthy child. Generally, the thickness of the endometrium is 8-12mm which is more suitable for implantation. The endometrium changes in thickness throughout the menstrual cycle as hormone levels change. The menstrual cycle is divided into proliferative phase, secretory phase, and menstrual phase, each with different thicknesses. 1. proliferative phase: the 5th-14th days of menstruation, when the endometrium may slowly grow to 3-5mm; 2. secretory phase: 14-28 days, under the action of estrogen and progesterone, the endometrium will grow to 8-10mm, and some may also grow to 12mm, when the endometrium is softer, richer in nutrients, and easier to implant. The endometrium will be softer, richer in nutrients, and easier to be implanted. If the endometrium is too thick, there is a possibility of endometrial lesions, such as endometrial polyps, small submucosal fibroids or abnormal hyperplasia of the endometrium. If you want to do IVF, the endometrium is more than 12mm, you usually have to do hysteroscopy or diagnostic scraping to exclude the lesion of endometrium; 3. Menstrual period: On the 1st-4th days of menstruation, the endometrium is thinner, usually around 2mm. The endometrium is 14mm and can be controlled with medication to keep the endometrium at 8-12mm, which is a thickness more likely to allow fertilization of the egg. If there is no abnormal bleeding and you are ready to conceive naturally, you can also use progesterone to make the lining peel off first. After the bleeding, the lining will come off cleanly and the ultrasound will be repeated to check the thickness of the lining. If the thickness is around 2mm on the 1st-4th day of menstruation, i.e., during the menstrual period, you can start normal preparation for pregnancy during ovulation.