Endometriumdicke in der Sonographie – ein wichtiger Parameter der endometrialen Rezeptivität?

Ultrasound is regularly used in reproductive medicine to assess endometrial thickness (EMT) before embryo transfer is carried out in order to use the EMT as a prognostic parameter for the likelihood of embryo implantation. Whether this really is reasonable is controversially discussed in the literature because factors, such as maternal age and ovarian response to ovarian stimulation by in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles are important confounders of the thickness of the endometrium. In a meta-analysis the EMT provided a limited possibility to filter out women with a low chance of becoming pregnant; however, cases below the threshold of an EMT ≤7 mm are rare. Ultimately, the association between a low EMT and the probability of pregnancy is not strong, so that termination of the cycle or postponement of embryo transfer is not generally recommended. In a unicenter retrospective study with 11,000 IVF/ICSI cycles, it was shown that EMT is an independent prognostic factor for clinical pregnancy, live birth and for the risk for spontaneous abortion and extrauterine gravidity; however, the effect size is also small. Another larger retrospective analysis showed that in univariate analysis the rate of ongoing pregnancies correlates with the thickness of the endometrium and that the chance for conceiving is statistically better with an EMT ≥ 9 mm than with values between 3 mm and 8 mm. Nevertheless, the EMT is only a poor prognostic factor because the expected increase in live birth rates with increasing EMT is low. For this reason further therapeutic consequences should not be deduced from the height of the EMT for IVF or ICSI therapy.