This was a prospective cross-sectional study. The
study protocol was reviewed and approved by the Ethical
Committee of Medical Faculty of Bozok University.
Patients provided informed consent to participate.
We used two protocols, agonist (n=135) or antagonist
(n=458) as previously described (
Follicular development was monitored and dose adjusment performed according to the E2 level and ultrasonographic measurements. The endometrial thickness was measured by the same clinician utilizing TVUSG. When 1 or 2 follicles reached 17 mm in size, hCG (Pregnyl® 5000 IU×2, Schering-Plough, USA) was administered for final maturation. TV- USGguided needle aspiration of the follicular fluid was carried out 35 to 36 hours after hCG administration. ICSI was performed in all cases. Cleavage stage embryos were transferred into the uterine cavity on day 3 or 5. A maximum of two embryos were transferred under transabdominal ultrasound guidance. Luteal phase was supported by administering transvaginal progesterone (Crinone 8% Vaginal Gel®, Merck-Serono, Switzerland) on the oocyte pick-up day and continued for 12 days (until the serum pregnancy test). Clinical pregnancy was confirmed by the presence of a fetal sac or fetal cardiac activity at ultrasound examination two weeks after the pregnancy test.
Statistical analyses were performed using the Statistical Package for the Social Sciences (version 17.00, SPSS Inc., Chicago, IL). Data normality was assessed with the Kolmogorov-Smirnov test. Data were compared by nonparametric analysis and statistical significance was determined by the Kruskal-Wallis test. Statistical comparisons between groups were performed using the Mann-Whitney U and chi square tests. A p value <0.05 was considered significant.
Patient characteristics such as basal hormone levels, duration of infertility, body mass index (BMI), antral follicle count (AFC) and age were analyzed. The groups were homogeneous in terms of these parameters. We excluded cases in which testicular sperm extraction (TESE) procedures were performed. Also patients, whose BMI was >30, were excluded. All patients underwent standard IVF-ICSI procedures. One cycle was used for each patient.
A total of 593 women whose ages ranged
from 20 to 39 years were included in the analysis.
The patient characteristics are shown in
table 1. Patients’ age, duration of infertility,
basal FSH levels, basal E2 levels, BMI, and
AFC were compared but the differences were
not statistically significant. The endometrial
thickness ranged from 6.1 mm to 21.4 mm. Although
no threshold was observed above which
a pregnancy was unlikely to occur, clinical
pregnancy rate (CPR) was significantly lower
in cases with an endometrial thickness below 7
Clinical pregnancy rates according to the endometrial line. EL; endometrial line.
Retrieved oocyte number, transferred embryo
number, and the fertilization, cleavage, and implantation
rates (IR) were similar in all four groups.
Implantation rate, CPR, and ongoing pregnancy
rate (OPR) were significantly lower in group 1
than the other three groups (p<0.05). However,
there was no significant difference among groups
2, 3 and 4 (
Distribution of patients’ characteristics
|Group 1 (N=14)||Group 2 (N=177)||Group 3 (N=366)||Group 4 (N=36)||P value|
|27 ± 4.5||25.6 ± 3.9||27.3 ± 4.8||28.6 ± 5.7||Ns|
|5.7 ± 1.1||6.7 ± 1.3||5.9 ± 1.4||4.9 ± 1.1||Ns|
|8.7 ± 2.1||7.4 ± 1.8||7.7 ± 1.5||7.0 ± 1.1||Ns|
|47 ± 10.5||44 ± 9.7||41 ± 8.5||50.7 ± 12.5||Ns|
|9.0 ± 5.2||7.9 ± 4.7||6.9 ± 4.3||8.0 ± 3.3||Ns|
|24.8 ± 4.9||26.4 ± 5.4||28.4 ± 5.5||25.2 ± 6.1||Ns|
Ns; Nonsignificant, DI; Duration of infertility, Bas. FSH; Basal FSH, Bas. E2; Basal E2, AFC; Antral follicle count and BMI; Body mass index.
Group 1; Endometrial line <7 mm, Group 2; Endometrial line 7-10 mm, Group 3; Endometrial line 10-14 mm and Group 4; Endometrial line >14 mm.
Comparison of IVF-ICSI outcomes according to endometrial thickness on hCG day
|Group 1 (N=14)||Group 2 (N=177)||Group 3 (N=366)||Group 4 (N=36)|
|10.1 ± 6.6||9.4 ± 5.8||10.8 ± 7.3||11.4 ± 7.6|
|1.3 ± 0.5||1.3 ± 0.6||1.2 ± 0.3||1.4 ± 0.6|
|64.5 (91/141)||65.6 (1105/1685)||68.2 (2541/3724)||68.0 (273/398)|
|60.2 (85/141)||63.0 (1063/1685)||64.0 (2384/3724)||61.0 (243/398)|
|11.1 (2/18)*||20.9 (82/391)*||24.3 (188/771)*||24.4 (19/78)*|
|14.3 (2/14)*||45.7 (81/177)*||48.6 (178/366)*||47.2 (17/36)*|
|7.1 (1/14) *||35.5 (63/177)*||43.9 (161/366)*||41.7(15/36)*|
RON; Retrieved oocyte number, TEN; Transferred oocyte number, FR; Fertilization rate, CR; Cleavage rate, IR; Implantation rate, CPR; Clinical pregnancy rate and OPR; Ongoing pregnancy rate. Group 1; Endometrial line <7 mm,Group 2; Endometrial line 7-10 mm, Group 3; Endometrial line 10-14 mm and Group; Endometrial line >14 mm.
Values are mean ± SD and *; P<0.05.
Distribution of endometrial thickness according to stimulation protocol
|Group 1||Group 2||Group 3||Group 4|
|N (%)||EL (mm)||N (%)||EL (mm)||N (%)||EL (mm)||N (%)||EL (mm)|
|0||-||38 (21.5)||9.3 ± 1.2a||86 (23.5)||13.1 ± 1.6a||11 (30.5)||17.4 ± 2.1|
|14 (100)||6.5 ± 0.6||139 (78.5)||7.8 ± 0.9b||280 (76.5)||11.2 ± 1.1b||25 (69.5)||16.3 ± 1.8|
Thickness is presented as mean ± SD. EL; Endometrial line, n; Number of patients, AP; Agonist protocol and AnP; Antagonist protocol.
Although measurement of endometrial thickness is
commonly utilized in clinical practice during assisted
reproduction treatment, there are conflicting results regarding
the association between endometrial line and
IVF-ICSI outcome. Al-Ghamdi et al. have analyzed
2464 cycles and reported a positive linear relationship
between the endometrial thickness measured on the day
of hCG injection and CPR (
In this prospective cross-sectional study, the relationship
between endometrial line and IVF-ICSI outcome was studied. Our study showed a positive correlation between
endometrial thickness and CPR. To our knowledge,
this study has agreed with previous studies (
There were only two clinical pregnancies (14.3%) in
the current study that had an endometrial line less than 7
mm, of which one was lost. In our study the thinnest endometrial
stripe was 6.1 mm. When CPR was compared
with each millimeter of the endometrial line we found
that the pregnancy rates decreased below the 7 mm
thickness level. CPR was significantly lower in group
1 than the other groups. However, the difference among
groups 2, 3, and 4 were not statistically significant. Chen
reported that CPR was 23.0% (12/52) in patients whose
endometrial line was below 7 mm (
Implantation is necessary for a successful pregnancy
and requires a healthy endometrial receptivity (
In light of these data, the measurement of endometrial
thickness on the day of hCG administration remains important.
Several studies have reported that CPR increases
as endometrial thickness increases (
We have researched the association between endometrial thickness and IVF-ICSI outcome. Our results indicate that close monitoring of the endometrial line during IVF-ICSI treatment is recommended. Eventhough there is a lack of agreement with regards to the minimum endometrial thickness required for a successful pregnancy, our results suggest that CPR will be low when the endometrial thickness is less than 7 mm. However, large prospective and randomized trials are required to assess the predictive value of endometrial thickness measurement.