Table 1.
Baseline characteristics of frozen embryo resuscitation transfer cycles.
| Group 1 (≤1 year) | Group 2 (1 < group < 6 years) | Group 3 (≥6 years) | P value | |
|---|---|---|---|---|
| Number of cycles, n | 40,461 | 6337 | 208 | NA |
| Age (FET), mean (SD), y | 31.29 ± 4.10 | 32.71 ± 3.83 | 34.88 ± 3.04 | <.001 |
| Age (OPU), mean (SD), y | 30.78 ± 4.11 | 30.44 ± 3.92 | 27.97 ± 2.95 | <.001 |
| BMI, mean (SD) | 21.89 ± 3.07 | 21.86 ± 2.99 | 21.24 ± 2.63 | .002 |
| FSH, mean (SD) | 7.73 ± 3.32 | 7.40 ± 3.40 | 6.20 ± 2.21 | <.001 |
| P median (IQR) | 0.62 (0.42,0.91) | 0.63 (0.43,0.94) | 0.64 (0.40,0.95) | .01 |
| E2, median (IQR) | 46 (34,61) | 47 (35,63) | 52 (39,67) | <.001 |
| LH, median (IQR) | 4.25 (3.11,5.96) | 4.25 (3.08,5.98) | 4.51 (3.25,6.67) | .24 |
| FET Endometrial thickness, mean (SD) | 9.60 ± 1.87 | 9.27 ± 2.02 | 9.92 ± 1.76 | <.001 |
| Duration of infertility, median (IQR), y | 3 (2,5) | 3 (2,5) | 4 (2,5) | <.001 |
| Infertility type, n (%) | ||||
| Primary | 20,080 (49.63) | 3035 (47.89) | 95 (45.67) | .02 |
| Secondary | 20,381 (50.37) | 3302 (52.11) | 113 (54.33) | |
| Infertility factors, n (%) | ||||
| Tubal factors | 31,427 (77.67) | 4146 (65.43) | 134 (64.42) | <.001 |
| Ovulation disorders | 431 (1.07) | 94 (1.48) | 0 | |
| The male factor | 5662 (13.99) | 1260 (19.88) | 48 (23.08) | |
| Others | 2941 (7.27) | 837 (13.21) | 26 (12.50) | |
| FET scheme, n (%) | ||||
| Hormone replacement | 26,565(65.66) | 3697 (58.34) | 139 (66.83) | <.001 |
| GnRH-a downregulation | 3716 (9.18) | 704 (11.11) | 10 (4.81) | |
| Stimulation | 5191 (12.83) | 1057 (16.68) | 26 (12.50) | |
| Natural | 4989 (12.33) | 879 (13.87) | 33 (15.87) | |
| Number of embryos transferred, n (%) | ||||
| 1 | 12,433 (30.73) | 2152 (33.96) | 56 (26.92) | <.001 |
| 2 | 28,028 (69.27) | 4185 (66.04) | 152 (73.08) | |
| Type of embryo transfer, n (%) | ||||
| Cleavage embryo | 10,612 (26.23) | 2185 (34.48) | 9 (4.33) | <.001 |
| Blastocyst | 29,849 (73.77) | 4152 (65.52) | 199 (95.67) | |
| Number of high-quality embryo transfers, n (%) | ||||
| 0 | 13,171 (32.55) | 2356 (37.18) | 139 (66.83) | <.001 |
| 1 | 13,296 (32.86) | 2211 (34.89) | 51 (24.52) | |
| 2 | 13,994 (34.59) | 1770 (27.93) | 18 (8.65) | |
IQR = Interquartile range, NA = Not applicable, Opu = Oocyte Pick-Up.