FIGURE 1.

The increasing dose (ID) regimen of hormone replacement cycle for frozen‐thawed embryo transfer (FET). Estrogen patches were replaced every 2 d and were increased gradually. The thickness of the endometrium was examined on the 14th day. From the next day, progestin tablets were administered vaginally one tablet at a time every 8 h. From the start of administration of progestin, the number of estrogen patches was fixed at 3. FET was performed on the 5th day of progestin administration. HRC, hormone replacement cycle; E₂, serum estradiol; P₄, serum progesterone; Em, thickness of endometrium; Fo, follicle development; hCG, serum human chorionic gonadotropin