A RCT Comparing Spontaneous Natural Cycles and Human Chorionic Gonadotrophin-induced Natural Cycles in FET

ultrasound scanning would be carried out from 18 days before the expected period to confirm follicular growth, followed by daily blood monitoring of serum E2 and LH levels when the dominant follicle reaches 13-14mm in diameter. Ultrasound scanning can be arranged accordingly if the leading follicle remains less than 10mm in diameter. 5 ml of blood would be taken daily. LH surge is defined as the LH level being double of the average of the previous three days and higher than 20 IU/L. Ultrasound examination will be performed on the next day after the LH surge to measure the endometrial thickness. The transfer will be scheduled three or four days after the LH surge (for cleavage stage embryos) or six days after LH surge (for blastocyst transfer).

ultrasound monitoring would be started from 18 days before the expected period to monitor follicular growth, followed by USG every 2-3 days. hCG, 5,000-10,000 IU will be given when the leading follicle is \>/= 17 mm and the endometrium measures \>/=8 mm. Serum E2, LH and progesterone levels will be measured on the day of hCG. Embryo transfer would be scheduled on the fourth or fifth days after hCG injection (for cleavage stage embryos) or seventh days (for blastocyst transfer).