Table 2 Cycle characteristics of FET
Characteristics | Underweight (< 18.5 kg/m2) | Normal weight (18.5–22.9 kg/m2) | Overweight (23–27.4 kg/m2) | Obese (≥ 27.5 kg/m2) | P valuea | P valueb | P valuec |
|---|---|---|---|---|---|---|---|
Patients, n | 2527 | 13,224 | 5079 | 1213 | Â | Â | Â |
Endometrial preparation | 0.400 | < 0.001 | < 0.001 | ||||
 Modified Natural cycle | 1202(47.6) | 6104(46.2) | 1961(38.6) | 356(29.3) |  | ||
 Stimulated cycles | 655(25.9) | 3479(26.3) | 1588(31.3) | 434(35.8) |  | ||
 Hormonal replacement | 670(26.5) | 3641(27.5) | 1530(30.1) | 423(34.9) |  | ||
Number of embryo transferred | 0.913 | 0.457 | 0.124 | ||||
 1 | 264(10.4) | 1372(10.4) | 508(10.0) | 143(11.8) |  | ||
 2 | 2263(89.6) | 11,852(89.6) | 4571(90.0) | 1070(88.2) |  | ||
Embryo developmental stage at transfer | 0.481 | < 0.001 | 0.007 | ||||
 Day 3 | 2382(94.3) | 12,417(93.9) | 4843(95.4) | 1162(95.8) |  | ||
 Day 5/6 | 145(5.7) | 807(6.1) | 236(4.6) | 51(4.2) |  | ||
Embryo quality | 0.201 | 0.584 | 0.158 | ||||
 Top quality | 553(21.9) | 3048(23.0) | 1190(23.4) | 258(21.3) |  | ||
 Good quality | 1974(78.1) | 10,176(77.0) | 3889(76.6) | 955(78.7) |  | ||
Post-thaw embryo survival rate | 4790/4812 (99.54) | 25,076/25,236 (99.37) | 9650/9707 (99.41) | 2283/2298 (99.35) | 0.147 | 0.618 | 0.914 |
Endometrium thickness on the day of embryo transfer (mm) | 11.33 ± 1.95 | 11.31 ± 2.04 | 11.37 ± 2.02 | 11.23 ± 1.94 | 0.613 | 0.069 | 0.164 |