Evaluating Endometrial Thickness at Antagonist Starting Day as an Adjuvant Criterion to Decide Gnrh Initiation in Flexible Antagonist Protocols

Abstract

Background Currently, GnRH antagonist protocols may be most prevalent protocols designed to prevent the luteinizing hormone surge in ICSI cycles, the flexible start protocols with more individualized timing of initiating the inhibition were mostly used, however; different criteria were proposed to determine the optimal time of GnRH antagonist administration, mostly leading follicular size was depended as criterion to start the inhibition. However; Leading follicular size, serum estradiol level, serum LH level was used in this study to initiate antagonist administration, and will correlate the endometrial thickness and pattern to the other optimal start criteria for antagonist administration and this is attributed for being noninvasive and easy method of assessment via transvaginal ultrasound, Objectives: Evaluate the optimal endometrial thickness at time of initiating GnRH antagonist in different groups of patients treated with ICSI and to correlate endometrial thickness at antagonist starting day and endometrial pattern with pregnancy rates. Materials and Methods: This prospective comparative observational study was made on one hundred twenty women who were experiencing ICSI flexible antagonist protocol at the High Institute for Infertility Diagnosis and Assisted Reproductive Technologies/Al-Nahrain University from October 2020 to April 2022, Cycles included were fresh transfer cycles and frozen cycles excluded. Those patients were randomized in to three groups according to the criterion they fulfilled to initiate the antagonist. Group A: 40 patients where the antagonist was started when the leading follicle size was (12-14). Group B: 40 patients where the antagonist was started when the serum E2 was exceeding 500pg/ml and group C: 40 patients where the antagonist was started when the serum LH level > 5 IU/l. vaginal ultrasound was used to assess the endometrial thickness and pattern in the three different groups during controlled ovarian hyper stimulation. Data were analyzed by (SPSS) version 26.0 using χ2, t-test, ANOVA, Fisher exact tests. “ROC curve” was also used to find the best cutoff value for continuous variables predicting pregnancy. Results: There was significant difference in endometrial thickness at antagonist day among study groups with (p= 0.016) and lowest endometrial thickness value being in the A group. There was no significant difference among the three study groups with regard to the endometrial thickness (mm) on the day of ovulation trigger (p= 0.060) with higher thickness was in the B group compared to other two groups. A highly significant difference (p= 0.001) regarding the presence of triple layer pattern at antagonist starting day was seen, 27(50%) of patients in the A group have no triple layer pattern, while higher percentage of patients 29(43.9%) have triple layer pattern in group B compared to other two groups. The difference was not significant in basal endometrial thickness between pregnant and non-pregnant groups, however, there was significant difference at antagonist day (p= 0.003) and highly significant difference was on trigger day (P= <0.001). Triple layer pattern was significantly higher in pregnant group. The best cutoff value of endometrial thickness at day of antagonist in predicting pregnancy was <6.45 Conclusion: The endometrial thickness at day of antagonist correlates significantly with pregnancy rates and it can be taken as criteria to initiate GnRH antagonist with a sensitivity level of 78 % and a specificity level 57%. Triple layer pattern was higher in pregnant group, but however, without statistical difference.