To evaluate the impact of single dose GnRH agonist administration as luteal phase support on pregnancy outcomes in frozen ICSI cycle

Assisted reproductive technologies (ART), particularly intracytoplasmic sperm injection (ICSI) with frozen embryo transfer, have significantly improved the outcomes of infertility treatment over the past decades. Despite these advances, implantation failure and suboptimal pregnancy rates remain important challenges. One of the critical factors influencing the success of embryo implantation is adequate luteal phase support, which ensures proper endometrial receptivity and maintenance of early pregnancy. (1_3) Progesterone supplementation has long been established as the standard method for luteal phase support in frozen ICSI cycles. It plays a fundamental role in transforming the endometrium into a receptive state suitable for embryo implantation and sustaining early gestation. However, despite its widespread use, pregnancy outcomes are not optimal in all cases, suggesting the need for additional or alternative therapeutic strategies to enhance reproductive success.(1_3) Recently, gonadotropin-releasing hormone (GnRH) agonists have gained increasing attention as a potential adjunct in luteal phase support protocols. It has been proposed that GnRH agonists may exert beneficial effects through multiple mechanisms, including stimulation of endogenous luteinizing hormone (LH) secretion, improved corpus luteum function, and enhanced progesterone production. Additionally, emerging evidence suggests a possible direct effect on the endometrium and embryo-endometrial interaction, which may further improve implantation potential.(4-7) Despite promising findings from several randomized controlled trials and meta-analyses, the role of GnRH agonists in luteal phase support remains controversial. Some studies have demonstrated improved implantation and clinical pregnancy rates, while others have reported no significant benefit compared to conventional progesterone therapy alone. This inconsistency is particularly evident in frozen ICSI cycles, where hormonal dynamics differ from fresh cycles.Therefore, further well-designed prospective studies are required to clarify the effectiveness of GnRH agonists in luteal phase support and to determine their potential role in improving reproductive outcomes

Inclusion Criteria:

• 1. Age 20-39 years 2. Undergoing HRT-FET cycle 3. ≥1 good quality embryo available , Gardner ≥3BB 4. Endometrial thickness ≥7mm on day of progesterone start 5. BMI 18-35 kg/m² 6. First or second FET cycle 7. Written informed consent

Exclusion Criteria:

• 1. History of recurrent implantation failure ≥3 failed embryo transfers 2. Severe endometriosis Stage III-IV by ASRM 3. Uterine anomalies, submucous fibroid, or severe adenomyosis distorting cavity 4. History of recurrent pregnancy loss ≥2 consecutive 5. Contraindication or hypersensitivity to GnRH agonist 6. PGT-A cycles 7. Donor oocyte cycles

women only