GnRH agonist pretreatment prior to frozen embryo transfer in women with adenomyosis: a systematic review and meta-analysis

The aim of this study was to investigate whether gonadotrophin-releasing hormone agonist (GnRHa) pretreatment has a positive effect on pregnancy outcomes in women with adenomyosis who were undergoing a frozen embryo transfer (FET) cycle. A systematic search of the PubMed, Embase and Cochrane databases up to 20 March 2025 was conducted. The primary outcome was live birth rate, while secondary outcomes were the clinical pregnancy, implantation and miscarriage rates. Seven retrospective cohort studies and one randomized trial met the inclusion criteria. The meta-analysis of studies comparing GnRHa pretreatment plus hormone replacement therapy (HRT)-FET with HRT-FET alone in women with adenomyosis showed a comparable live birth rate (six studies, odds ratio [OR] 1.19, 95% CI 0.69-2.06, I2 = 74%), clinical pregnancy rate (seven studies, OR 1.36, 95% CI 0.83-2.23, I2 = 80%), miscarriage rate (six studies, OR 1.09, 95% CI 0.69-1.74, I2 = 20%) and implantation rate per embryo transfer (three studies, OR 1.38, 95% CI 0.59-3.24, I2 = 90%). Current evidence does not demonstrate the superiority of GnRHa pretreatment plus HRT over HRT alone in women with adenomyosis prior to FET. Future randomized trials are needed to determine the optimal protocol for FET in this population.