Table 1.
Demographic characteristics of the study population
| Characteristics | Patients were equally divided into three groups according to the peak E2 level from low to high | P low versus middle | P high versus middle | |||
|---|---|---|---|---|---|---|
| n = 1141 | Low (n = 380) | Intermediate (n = 380) | High (n = 381) | |||
| Peak E2 level on hCG trigger day (100 pg/ml) | 39.1 ± 13.0 | 24.6 ± 5.9 | 39.4 ± 3.3 | 53.3 ± 7.0 | < 0.001 | < 0.001 |
| Female age (years) | 30.0 ± 3.7 | 30.5 ± 3.8 | 30.0 ± 3.7 | 29.5 ± 3.5 | 0.042 | 0.056 |
| BMI (kg/m2) | 22.1 ± 2.8 | 22.5 ± 3.0 | 22.1 ± 2.8 | 21.6 ± 2.5 | 0.030 | 0.020 |
| Infertility duration (years) | 3.8 ± 2.7 | 3.8 ± 2.8 | 3.6 ± 2.4 | 3.9 ± 2.8 | 0.244 | 0.119 |
| Basal AFC | 16.8 ± 6.7 | 14.5 ± 6.0 | 17.3 ± 7.0 | 18.5 ± 6.4 | < 0.001 | 0.020 |
| Basal FSH (IU/L) | 7.3 ± 3.3 | 7.4 ± 2.7 | 7.1 ± 2.8 | 7.2 ± 3.1 | 0.076 | 0.680 |
| Basal E2 (pg/ml) | 53.8 ± 35.5 | 53.7 ± 40.2 | 55.0 ± 33.0 | 52.6 ± 33.0 | 0.639 | 0.325 |
| Infertility etiology (data missing, n = 2) | 0.398 | 0.808 | ||||
| Tubal factor (n [%]) | 653 (57.2) | 232 (61.1) | 205 (54.0) | 216 (56.7) | ||
| Male factor (n [%]) | 126 (11.0) | 38 (10.0) | 43 (11.3) | 45 (11.8) | ||
| Mixed factor (n [%]) | 291 (25.5) | 86 (22.6) | 105 (27.6) | 100 (26.3) | ||
| Endometriosis (n [%]) | 5 (0.4) | 2 (0.5) | 2 (0.5) | 1 (0.3) | ||
| Unexplained (n [%]) | 66 (5.8) | 22 (5.8) | 25 (6.6) | 19 (5.0) | ||
| Stimulation protocol | < 0.001 | 0.543 | ||||
| GnRH-agonist protocol (n [%]) | 1071 (93.9) | 329 (86.6) | 371 (97.6) | 371 (97.4) | ||
| GnRH-antagonist protocol (n [%]) | 69 (6.1) | 51 (13.4) | 8 (2.1) | 10 (2.6) | ||
| Other (n [%]) | 1 (0.1) | 0 (0.0) | 1 (0.3) | 0 (0.0) | ||
| Duration of stimulation (days) | 11.3 ± 2.1 | 11.3 ± 2.0 | 11.6 ± 2.4 | 11.0 ± 2.0 | 0.104 | < 0.001 |
| Follicular count on hCG day (≥ 14 mm)Follicular count on hCG day (≥ 14 mm)Follicular count on hCG day (≥ 14 mm) | 11.2 ± 3.6 | 8.70 ± 3.2 | 11.9 ± 3.2 | 13.0 ± 2.9 | < 0.001 | < 0.001 |
| Total dose of Gn administered (IU) | 1953.4 ± 898.9 | 2349.3 ± 963.0 | 1906.2 ± 868.3 | 1604.5 ± 682.2 | < 0.001 | < 0.001 |
| Number of oocytes retrieved | 13.6 ± 5.5 | 9.8 ± 3.9 | 14.3 ± 4.9 | 16.7 ± 5.0 | < 0.001 | < 0.001 |
| Method of fertilization | 0.462 | 0.957 | ||||
| IVF (n [%]) | 831 (72.8) | 288 (75.8) | 273 (71.8) | 270 (70.9) | ||
| ICSI (n [%]) | 241 (21.1) | 72 (19.0) | 83 (21.8) | 86 (22.6) | ||
| IVF + ICSI (n [%]) | 69 (6.1) | 20 (5.3) | 24 (6.3) | 25 (6.6) | ||
| Mean number of embryos transferred | 1.9 ± 0.4 | 1.9 ± 0.3 | 1.9 ± 0.3 | 1.8 ± 0.4 | 0.266 | 0.062 |
| Development of transferred embryos (data missing, n = 16) | 0.018 | 0.216 | ||||
| 1 or 2 Grade 1 D3 embryos (n [%]) | 231 (20.5) | 72 (19.2) | 80 (21.2) | 79 (21.2) | ||
| 1 or 2 Grade 2 D3 embryos (n [%]) | 487 (43.3) | 181 (48.1) | 153 (40.6) | 153 (41.1) | ||
| 1 Grade 1 and 1 Grade 2 D3 embryos (n [%]) | 274 (24.4) | 101 (26.9) | 97 (25.7) | 76 (20.4) | ||
| Single blastocyst (n [%]) | 124 (11.0) | 20 (5.3) | 43 (11.4) | 61 (16.4) | ||
| Embryo + blastocyst (n [%]) | 9 (0.8) | 2 (0.5) | 4 (1.1) | 3 (0.8) | ||
| Fresh or frozen embryo transfer | < 0.001 | < 0.001 | ||||
| Fresh embryo transfer (n [%]) | 377 (33.0) | 200 (52.6) | 121 (31.8) | 56 (14.7) | ||
| FET (n [%]) | 764 (67.0) | 180 (47.4) | 259 (68.2) | 325 (85.3) | ||
| Methods of endometrium preparation in FET cycles | < 0.001 | < 0.001 | ||||
| HRT (n [%]) | 321 (28.1) | 65 (17.1) | 106 (27.9) | 150 (39.4) | ||
| Natural ovulation cycle (n [%]) | 415 (36.4) | 107 (28.2) | 139 (36.6) | 169 (44.4) | ||
| Down-regulation cycle (n [%]) | 366 (32.1) | 198 (52.1) | 116 (30.5) | 52 (13.7) | ||
| Mild stimulation cycle (n [%]) | 39 (3.4) | 10 (2.6) | 19 (5.0) | 10 (2.6) | ||
| cLBR (n [%]) | 763 (66.9) | 251 (66.1) | 257 (67.6) | 255 (66.9) | 0.644 | 0.836 |
| Miscarriage rate (n [%]) | 84 (7.4) | 28 (7.4) | 24 (6.3) | 32 (8.4) | 0.565 | 0.271 |
| Preterm birth (n [%]) | 156 (13.7) | 45 (11.8) | 52 (13.7) | 59 (15.5) | 0.447 | 0.481 |
| Macrosomia (n [%]) | 66 (7.2) | 27 (9.1) | 26 (8.4) | 13 (4.2) | 0.758 | 0.028 |
| LBW (n [%]) | 151 (16.5) | 40 (13.5) | 52 (16.8) | 59 (18.9) | 0.256 | 0.510 |
| Congenital malformation (n [%]) | 1 (0.1) | 1 (0.3) | 0 (0.0) | 0 (0.0) | 0.311 | 0.654 |
| Perinatal death (n [%]) | 3 (0.3) | 2 (0.6) | 1 (0.3) | 0 (0.0) | 0.549 | 0.491 |
| Ectopic pregnancy (n [%]) | 2 (0.2) | 1 (0.3) | 0 (0.0) | 1 (0.3) | 0.311 | 0.325 |
| Heterotopic pregnancy (n [%]) | 2 (0.2) | 0 (0.0) | 1 (0.3) | 1 (0.3) | 0.323 | 0.980 |
| Moderate to severe OHSS (n [%]) | 5 (0.5) | 0 (0.0) | 4 (1.2) | 1 (0.3) | 0.047 | 0.166 |
| Gestational hypertension (n [%]) | 1 (0.1) | 0 (0.0) | 0 (0.0) | 1 (0.3) | 0.755 | 0.325 |
| Live births | ||||||
| Singletons (n [%]) | 654 (71.3%) | 219 (74.0%) | 230 (74.7%) | 205 (65.5%) | 0.846 | 0.013 |
| Twins (n [%]) | 263 (28.7%) | 77 (26.0%) | 78 (25.3%) | 108 (34.5%) | ||
AFC antral follicular count, BMI body mass index, cLBR cumulative live birth rate, E2 estradiol, FET frozen embryo transfer, FSH follicular stimulating hormone, hCG human chorionic gonadotropin, HRT hormone replacement treatment, IVF in vitro fertilization, ICSI intracytoplasmic single sperm injection, LBW low birth weight