Table 1.
Baseline characteristics of sample population stratified by ovarian stimulation protocols (n = 38,220)a.
| Characteristics | Natural cycle (n = 4058) | Clomiphene alone (n = 4715) | Clomiphene + gonadotropin (n = 5443) | GnRH agonist (n = 16566) | GnRH antagonist (n = 7438) | P valueb |
|---|---|---|---|---|---|---|
| Maternal age, (year) | 35.3 (3.6) | 35.8 (3.7) | 34.7 (3.9) | 34.2 (3.7) | 34.7 (3.9) | <0.001 |
| <30 | 253 (6.2) | 250 (5.3) | 533 (9.8) | 1808 (10.9) | 697 (9.4) | <0.001 |
| 30–34 | 1367 (33.7) | 1421 (30.1) | 2010 (36.9) | 6737 (40.7) | 2774 (37.3) | |
| 35–39 | 1927 (47.5) | 2318 (49.2) | 2333 (42.9) | 6860 (41.4) | 3172 (42.7) | |
| ≥40 | 511 (12.6) | 726 (15.4) | 566 (10.4) | 1161 (7.0) | 795 (10.7) | |
| Infertility diagnosisc | ||||||
| Tubal factor | 494 (12.2) | 542 (11.5) | 789 (14.5) | 3721 (22.5) | 1340 (18.0) | <0.001 |
| Endometriosis | 174 (4.3) | 235 (5.0) | 365 (6.7) | 1718 (10.4) | 658 (8.9) | <0.001 |
| Antisperm antibody | 11 (0.27) | 9 (0.19) | 42 (0.77) | 187 (1.1) | 74 (0.99) | <0.001 |
| Male factor | 656 (16.2) | 895 (19.0) | 1503 (27.6) | 5363 (32.4) | 2666 (35.8) | <0.001 |
| Unexplained | 2684 (66.1) | 3007 (63.8) | 2602 (47.8) | 5864 (35.4) | 2600 (35.0) | <0.001 |
| Others | 235 (5.7) | 212 (4.5) | 729 (13.4) | 1666 (10.1) | 1084 (14.6) | <0.001 |
| Number of oocytes retrieved | 1.2 (0.69) | 2.0 (1.2) | 3.9 (2.8) | 8.6 (5.0) | 7.6 (4.8) | <0.001 |
| 1 | 3586 (88.4) | 1752 (37.2) | 815 (15.0) | 455 (2.8) | 399 (5.3) | <0.001 |
| 2–3 | 433 (10.7) | 2543 (53.9) | 2184 (40.1) | 1807 (10.9) | 1102 (14.8) | |
| 4–9 | 34 (0.84) | 406 (8.6) | 2181 (40.1) | 8172 (49.3) | 3762 (50.6) | |
| ≥10 | 5 (0.12) | 14 (0.30) | 263 (4.8) | 6132 (37.0) | 2175 (29.2) | |
| Fertilization method | ||||||
| IVF | 2160 (53.2) | 2303 (48.8) | 2792 (51.3) | 8234 (49.7) | 2987 (40.2) | <0.001 |
| ICSI | 1847 (45.5) | 2102 (44.6) | 2196 (40.4) | 6219 (37.5) | 3534 (47.5) | |
| Split (IVF + ICSI) | 51 (1.3) | 310 (6.6) | 455 (8.4) | 2113 (12.8) | 917 (12.3) | |
| Embryo stage at transfer | ||||||
| Early cleavage | 3542 (87.3) | 4509 (95.6) | 4303 (79.1) | 9044 (54.6) | 4323 (58.1) | <0.001 |
| Blastocyst | 516 (12.7) | 206 (4.4) | 1140 (20.9) | 7522 (45.4) | 3115 (41.9) | |
| Luteal supportc | ||||||
| None | 358 (8.8) | 161 (3.4) | 290 (5.3) | 160 (0.97) | 78 (1.1) | <0.001 |
| Progesterone | 3326 (82.0) | 3466 (73.5) | 2563 (47.1) | 4828 (29.1) | 2061 (27.7) | <0.001 |
| hCG | 58 (1.4) | 758 (16.1) | 199 (3.7) | 1607 (9.7) | 337 (4.5) | <0.001 |
| Progesterone + hCG | 196 (4.8) | 182 (3.9) | 1013 (18.6) | 4605 (27.8) | 2034 (27.4) | <0.001 |
| Estrogen + Progesterone | 126 (3.1) | 164 (3.5) | 1357 (24.9) | 5813 (35.1) | 3247 (43.7) | <0.001 |
| Others | 15 (0.37) | 24 (0.51) | 200 (3.7) | 1013 (6.1) | 183 (2.5) | <0.001 |
| Yeard | ||||||
| 2007 | 343 (9.6) | 535 (15.0) | 532 (14.9) | 1625 (45.5) | 533 (14.9) | <0.001 |
| 2008 | 342 (7.7) | 470 (10.6) | 622 (14.0) | 2259 (50.7) | 764 (17.1) | |
| 2009 | 500 (8.8) | 614 (10.8) | 790 (13.9) | 2688 (47.2) | 1100 (19.3) | |
| 2010 | 537 (9.4) | 716 (12.5) | 808 (14.1) | 2457 (42.8) | 1223 (21.3) | |
| 2011 | 624 (10.4) | 692 (11.5) | 832 (13.9) | 2524 (42.1) | 1326 (22.1) | |
| 2012 | 876 (13.7) | 842 (13.2) | 887 (13.9) | 2526 (39.6) | 1251 (19.6) | |
| 2013 | 836 (13.1) | 846 (13.3) | 972 (15.2) | 2487 (39.0) | 1241 (19.5) | |
aData are presented as mean (SD) for continuous variables and n (%) for dichotomous variables.
bP values were assessed with the use of χ2 or one-way analysis of variance.
cMultiple answers were allowed.
dPercentages for rows for the purpose of comparison.
ART, assisted reproductive technology; ICSI, intracytoplasmic sperm injection; IVF, in vitro fertilization