The normal range of endometrial thickness during menstruation should be about 1 cm. If the endometrial thickness is less than 5 mm or more than 15 mm, it is abnormal.
The thickness of the endometrium varies with the ovarian cycle. Estrogen and progesterone affect the thickness of the endometrium, and the endometrium is in the hyperplasia phase from the 5th day of the menstrual cycle onwards and will continue to thicken. In the second half of the menstrual cycle, the lining is in the secretory phase and can be up to 1 centimeter thick.
If the thickness of the endometrium is less than 7 millimeters throughout the menstrual cycle, it means that the endometrium is thin, and there may be endocrine disorders or uterine adhesions, which can affect pregnancy. If a woman has an endometrial thickness of more than 15 millimeters before her menstrual period, the endometrium is thicker and she may have abnormally elevated estrogen levels or endometrial polyps.
It is recommended that women go to the hospital about three days before their period for a vaginal ultrasound to check if the thickness of the endometrium is normal.