Endometrial receptivity is one of the most important factors in the implantation process. The role of an ultrasonographic evaluation of the endometrium in predicting the implantation rate has long been debated. Although many studies consider a trilaminar echogenic pattern and endometrium thickness within a definite range as favorable prognostic factors (
Estrogen is essential for implantation because of its effects on both endometrial proliferation and the augmentation of uterine perfusion. Although its concentration has been predicted to be associated with endometrial thickness, the results of investigations are conflicting (
Thus, we aimed to investigate the effects of serum estradiol (E2) and progesterone levels on preovulatory endometrial thickness and echogenicity in COH cycles for
In this retrospective study approved by the Institutional Review Board (IRB) of Istanbul Faculty of Medicine, we evaluated the data of 241
Endometrial thickness and the echogenic pattern were evaluated on the day of hCG administration by transvaginal ultrasound, performed by four specialists. Endometrial thickness was defined as the greatest anteroposterior dimension in the sagittal plane. The cases were classified in three groups according to the measurement of endometrial thickness: ≤8 mm, 8-14 mm, and ≥14 mm. Echogenic patterns were described as trilaminar (hypoechogenic endometrium with central and outer echogenic lines), isoechogenic (same reflectivity compared to myometrium), and hyperechogenic (increased reflectivity compared to myometrium). Serum E2 levels in pg/ml and progesterone levels in ng/ml were evaluated on the day of hCG administration as a routine procedure in our clinic.
Data were analyzed using the χ2 test, Student’s t test, and analysis of variance (ANOVA), using statistical package for Windows, (version 9.0) (SPSS Inc., Chicago, IL). A p value of <0.05 was considered significant.
The patient characteristics are summarized in table 1. Endometrial thickness was measured as ≤8 mm (group 1) in 51 cases, 8-14 mm (group 2) in 182 cases, and ≥14 mm (group 3) in 8 cases (
Summary of demographic data
|31.3 ± 5.4|
|7.3 ± 4.5|
|1.5 ± 1|
* Values are mean ± SD.
The echogenic patterns are compared in table 3. Patients were older and the total gonadotropin dose was higher in the hyperechogenic group. However, we could not find a significant difference among the steroid hormone concentrations on the day of hCG administration.
Among the 241 COH cycles, 64 cycles resulted in pregnancies, with a total pregnancy rate of 26.6%.
Comparisons of variables between the groups according to endometrial thickness
|Variable||Group 1 (n = 51)||Group 2 (n = 182)||Group 3 (n = 8)||P-value|
|31.33 ± 5.09||31.38 ± 5.55||31.50 ± 5.86||0.99|
|3025.39 ± 1379.53||3308.58 ± 1329.41||3309.37 ± 2031.31||0.42|
|3079.75 ± 2010.33||3090.45 ± 1815.77||3232.33 ± 2617.99||0.98|
|1.40 ± 1.06||1.52 ± 1.46||1.06 ± 0.33||0.70|
|13.43 ± 7.81||12.71 ± 7.03||12 ± 8.7||0.77|
|2.71 ± 0.64||2.80 ± 0.50||2.63 ± 0.52||0.37|
* Values are mean ± SD.
Comparisons of variables between the groups according to endometrial echogenicity
|Variable||Trilaminar (n = 184)||Isoechogenic(n = 24)||Hyperechogenic (n = 33)||P-value|
|30.82 ± 5.33||33.04 ± 5.46||33.27 ± 5.57||0.01|
|3133.32 ± 1334.31||3467.79 ± 1202.42||3731.06 ± 1549.09||0.04|
|3112.40 ± 1678.30||2835.17 ± 2307.44||3190 ± 2552.42||0.79|
|1.50 ± 1.38||1.81 ± 1.84||1.12 ± 0.59||0.25|
|13.54 ± 7.37||11.79 ± 5.62||9.70 ± 6.72||0.01|
|2.81 ± 0.49||2.83 ± 0.48||2.55 ± 0.71||0.02|
* Values are mean ± SD.
The serum E2 levels were 3166.89 ± 1713.02 pg/ml in the conception cycles and 3066.70 ± 1930.27 pg/ml in the non-conception cycles. Serum progesterone levels were 1.48 ± 1.32 ng/ml in the conception and 1.48 ± 1.39 ng/ml in the non-conception cycles. There were no significant differences between conception and non-conception cycles in the means of steroid hormone levels.
The endometrium is a highly dynamic tissue changing cyclically in response to steroid hormones in order to create a window of receptivity for implantation (
Because progesterone is the hormone responsible for the secretory changes in the endometrium, we expected to find higher progesterone levels in the hyperechogenic group. Unexpectedly, it was insignificantly lower for the hyperechogenic pattern than the trilaminar or isoechogenic patterns. This is consistent with the results of other studies (
In our study, the sonographic appearance of endometrium was evaluated by four specialists using the same ultrasound device. Although this is expected to affect the results, Spandorfer et al. have reported that there is excellent correlation between intraobserver and interobserver measurement of the endometrium (
We showed that steroid levels on the day of hCG administration did not affect the ultrasound appearance of the endometrium. The thickness of the endometrium was not related to serum E2 levels. Different unknown mechanisms produced hyperechogenicity, other than premature exposure to progesterone. Further studies should be done to explore these mechanisms.