Frozen Embryo Transfer Protocols

In this study, all the embryos were vitrified. Frozen embryo transfer (FET) can be performed in the second menstrual cycle or later. Endometrial preparation protocols included the natural cycle, artificial cycle, induced ovulation cycle and downregulation + artificial cycle, which were mainly based on whether the patient’s ovulation was normal or not, and were also combined with the patient’s timing. The natural cycle was mainly used for women with regular menstrual cycles and spontaneous ovulation. Follicular development was monitored by transvaginal ultrasound, luteal-phase support was applied on the day of ovulation with oral dydrogesterone (2 times daily, 10 mg once) (Abbott Co. America) and intravaginal administration of 90 mg of a progesterone sustained-release vaginal gel (Merck Co. Germany), and 1-2 cleavage stage embryos were transferred 3 days later or 1 blastocyst was transferred 5 days later. The artificial/induced ovulation cycle for women with irregular menstrual cycles was done as previously reported (17 (link)). Downregulation + artificial protocols were used for women with endometriosis. GnRH agonist 3.75 mg was applied on the 2nd-3rd day of the menstrual cycle, and 28-30 days later, the endometrium was prepared with the artificial cycle. In women with clinical pregnancy, luteal-phase support was continued at least until 55 days after FET.