Table 1.
Demographic and ART characteristics.
| Primary singletons(n=6853) | Primary twins(n=2788) | Twins reduced to singletons (n=126) | Triplets reduced to singletons (n=45) | Triplets reduced to twins (n=331) | P value 1 | P value 2 | P value 3 | P value 4 | P value 5 | |
|---|---|---|---|---|---|---|---|---|---|---|
| Maternal age at conception | 30 (28-33) | 30 (28-33) | 33 (29-35) | 30 (28-35) | 31 (28-34) | <0.001 | 0.616 | 0.474 | <0.001 | <0.001 |
| Maternal height before pregnancy | 160.0 (157.0-163.0) | 160.0 (157.0-163.0) | 159.0 (155.0-162.3) | 158.0 (156.0-160.0) | 160.0 (157.0-163.0) | 0.786 | 0.123 | 0.118 | 0.056 | 0.073 |
| Maternal weight before pregnancy | 55.0 (50.4-60.0) | 55.0 (51.0-61.0) | 56.0 (50.9-60.1) | 53.0 (48.0-58.8) | 55.0 (51.0-60.0) | 0.426 | 0.090 | 0.087 | 0.778 | 0.558 |
| Maternal BMI before pregnancy | 21.6 (20.0-23.6) | 21.7 (20.0-23.9) | 22.2 (20.3-23.9) | 20.9 (19.5-23.4) | 21.6 (20.0-23.7) | 0.407 | 0.242 | 0.203 | 0.346 | 0.070 |
| Type of infertility | 0.005 | 0.004 | 0.070 | 0.026 | 0.048 | |||||
| Primary infertility | 3054 (44.6) | 1278 (45.8) | 45 (35.7) | 14 (31.1) | 179 (54.1) | |||||
| Secondary infertility | 3799 (55.4) | 1510 (54.2) | 81 (64.3) | 31 (68.9) | 152 (45.9) | |||||
| ART methods | <0.001 | 0.073 | 0.435 | 0.125 | 0.212 | |||||
| IVF | 5774 (84.3) | 2374 (85.2) | 101 (80.2) | 36 (80.0) | 221 (66.8) | |||||
| ICSI | 1079 (15.7) | 414 (14.8) | 25 (19.8) | 9 (20.0) | 110 (33.2) | |||||
| Embryo transplantation | 0.070 | 0.094 | 0.934 | 0.134 | 0.775 | |||||
| Fresh-ET | 3460 (50.5) | 1561 (56.0) | 62 (49.2) | 23 (51.1) | 168 (50.8) | |||||
| Frozen-ET | 3393 (49.5) | 1227 (44.0) | 64 (50.8) | 22 (48.9) | 163 (49.2) | |||||
| Source of semen | 0.731 | 0.178 | 0.019 | 0.191 | 0.254 | |||||
| Ejaculated semen | 6623 (96.6) | 2668 (95.7) | 125 (99.2) | 41 (91.1) | 316 (95.5) | |||||
| Sperm aspiration | 154 (2.2) | 76 (2.7) | 1 (0.8) | 1 (2.2) | 8 (2.4) | |||||
| Donor Semen | 76 (1.1) | 44 (1.6) | 0 | 3 (6.7) | 7 (2.1) | |||||
| Reduction weeks | – | – | 8.3 (7.7-9.0) | 8.1 (7.7-8.6) | 8.0 (7.7-8.4) | – | 0.161 | – | – | – |
Data are presented as median (IQR) or number (%). Comparison of continuous variables was analyzed using Mann–Whitney U tests. Categorical variables were compared by using Chi-square tests or Fisher’s exact test. P value 1 represents for triplets reduced to twins versus primary twins; P value 2 represents for triplets reduced to twins versus triplets reduced to singleton; P value 3 represents for triplets reduced to singleton versus primary singleton; P value 4 represents for twins reduced to singleton versus primary twins; P value 5 represents for twins reduced to singleton versus primary singleton;
BMI, body mass index (kg/m2); ART, assisted reproduction technique; IVF, in vitro fertilization; ICSI, intracytoplasmic sperm injection; ET, embryo transplantation; TESA, testicular sperm aspiration; PESA, percutaneous epididymal sperm aspiration; MESA, microsurgical epididymal sperm aspiration. Sperm aspiration includes TESA, PESA, and MESA.