How Thick is a Normal Woman's Endometrium?
The endometrium is the tissue that lines the inner layer of the uterus. It has the unique characteristic of changing in thickness and composition throughout the menstrual cycle. The endometrium plays a crucial role in achieving pregnancy, both naturally and during assisted reproduction treatments, as it is the tissue where embryo implantation occurs. In fact, the thickness and appearance of the endometrium are key factors in predicting the success of fertility treatments.
Generally, the endometrium is considered optimal when it has a thickness between 6 and 10 mm and a trilaminar appearance during endometrial monitoring. This means that three different layers should be visible during ultrasound monitoring: a bright or white outer layer (hyperechogenic), a dark or grayish middle layer (hypoechoic), and a bright central line (hyperechogenic).
Several factors influence endometrial thickness:
- Sex hormones: Estrogens stimulate endometrial growth, while progesterone prepares the endometrium for implantation by inducing glandular secretion.
- Medical conditions: Endometrial polyps, uterine fibroids, and certain treatments, such as aspiration curettage, can affect endometrial thickness.
As mentioned earlier, endometrial thickness is a crucial factor in determining the success of a fertility treatment. For this reason, the endometrial monitoring ultrasound before embryo transfer is one of the key tests performed on women during treatment.
An optimal endometrial thickness during the periovulatory phase lies typically between 7 and 9 mm. Both an endometrium that is too thin (<6 mm) and one that is too thick (>20 mm) may have structural or functional abnormalities that can reduce implantation rates.
However, not only endometrial thickness but also its appearance has to be evaluated. The tissue should be homogeneous and free of structural abnormalities such as polyps, fibroids, or adhesions, as these can negatively impact implantation.
Each case must be evaluated and treated individually. Therefore, feel free to contact us for more information.