Abstract
Study question
What is the effect of endometrial compaction on live birth rate in frozen-thawed embryo transfer (FET) cycles?
Summary answer
In FET cycles with artificial endometrial preparation, the chance for live birth was significantly higher in cycles with endometrial compaction.
What is known already
Most studies conclude that thinner the endometrium poorer the pregnancy outcome. These studies mostly include measurements in the follicular phase. Since endometrial thickness indicates receptivity, one may expect the endometrial thickness measured on ET day to be more important to predict the outcome. However, few studies assessed endometrial thickness on ET day and unlike follicular phase studies conflicting results were obtained regarding pregnancy outcome. The change in endometrial thickness may be more valuable to predict the pregnancy outcome rather than a single measurement.
Study design, size, duration
Retrospective observational cohort study. 283 FET cycles in which all patients underwent artificial endometrial preparation were reviewed. Participants/materials, setting, methods: The inclusion criteria were artificial endometrial preparation, age between 20–38 years. The same protocol was applied to all patients for the endometrial preparation.The change of endometrial thickness between the end of estrogen phase and embryo transfer day was recorded. Any decrement is defined as endometrial compaction. The patients were grouped according to the changes of endometrial thicknesses as compaction and non-compaction.
Main results and the role of chance
Among 283 cycles, 89 had endometrial compaction and 194 did not have compaction. The clinical pregnancy, implantation and live birth rates were significantly higher in the compaction group when compared to non-compaction group (P values 0.007, 0.009, and 0.039, respectively). In order to evaluate the results according to the degree of compaction, we divided the patients into 5% compaction slices. The live birth rate was significantly higher in the 5–10% compaction group (P = 0.016). A multivariable logistic regression analysis was performed to examine the independent effects of different variables on live birth chance.In FET cycles with artificial endometrial preparation, the chance for live birth was significantly higher in cycles with endometrial compaction (OR: 2.352, 95% confidence interval {CI} 1.297–4.264, P = 0.005). A receiver operating characteristic (ROC) curve analysis was performed to evaluate whether there was a certain threshold of endometrial thickness at the end of estrogen phase for endometrial compaction to occur. The sensitivity and specificity of 9.25 mm at the end of estrogen phase calculated from the ROC curve were 76.4% and 58.8%, respectively (area under the curve: 0.701, 95% CI 0.640–0.763; P < 0.001).
Limitations, reasons for caution
The main limitations of the study were its retrospective nature, relatively small sample size and utilization of different ultrasound techniques at different measurements (using transvaginal ultrasound at the end of the estrogen phase and transabdominal ultrasound on ET day).
Wider implications of the findings: Recently a cohort study they found that endometrial compaction results in better pregnancy outcomes, similar to our findings. But, this is the first study to suggest a threshold value (9.2) for endometrial thickness before the commencement of progesterone in regards to increase the chance of compaction.
Trial registration number
Not applicable
Effect of developmental stage of embryo at freezing on pregnancy outcome of frozen-thawed embryo transfer
