Table 1.
The characteristics and the pregnancy outcomes of the NC and HRC groups
| NC group n = 6287 |
HRC group n = 10,235 |
P value | |
|---|---|---|---|
| Maternal age during the treatment cycle, yearsa | 36.5 ± 3.7 | 35.3 ± 4.0 | <0.001b |
| Number of embryos transferreda | 1.06 ± 0.25 | 1.16 ± 0.37 | <0.001b |
| Stage at embryo transfer, number/total number (%) | <0.001c | ||
| Blastocyst | 5520/6253 (88.3) | 8109/9952 (81.5) | |
| Cleavage | 733/6253 (11.7) | 1843/9952 (18.5) | |
| Assisted hatching, number/total number (%) | 3515/6287 (55.9) | 6815/10,235 (66.6) | <0.001c |
| Indication for assisted reproductive technology (%) | |||
| Tubal factor | 1175/6287 (18.7) | 1704/10,235 (16.6) | 0.001c |
| Endometriosis | 352/6287 (5.6) | 795/10,235 (7.8) | <0.001c |
| Antisperm antibody-positive | 24/6287 (0.4) | 78/10,235 (0.8) | 0.003c |
| Male factor | 1390/6287 (22.1) | 3165/10,235 (30.9) | <0.001c |
| Unexplained infertility | 3346/6287 (53.2) | 3921/10,235 (38.3) | <0.001c |
| Others | 553/6287 (8.8) | 2461/10,235 (24.0) | <0.001c |
| Mode of delivery, number/total number (%) | <0.001c | ||
| Vaginal delivery | 4173/6287 (66.4) | 5829/10,235 (57.0) | |
| Cesarean section | 2114/6287 (33.6) | 4406/10,235 (43.0) | |
| Sex of the neonate, number/total number (%) | 0.098c | ||
| Male | 3274/6269 (52.2) | 5283/10,158 (52.0) | |
| Female | 2995/6269 (47.8) | 4875/10,158 (48.0) | |
| Gestational age at birth, weeksa | 38.6 ± 1.8 | 38.8 ± 2.1 | <0.001b |
| Gestational age category, number/total number (%) | |||
| ≤36 weeks | 411/6287 (6.5) | 737/10,235 (7.2) | 0.103c |
| 37–41 weeks | 5861/6287 (93.2) | 9363/10,235 (91.5) | <0.001c |
| ≥42 weeks | 15/6287 (0.2) | 135/10,235 (1.3) | <0.001c |
| Birth weight, ga | 3046.0 ± 442.5 | 3059.5 ± 479.5 | 0.063d |
| Birth weight category, number/total number (%) | |||
| <2500 g | 499/6272 (8.0) | 922/10,209 (9.0) | 0.017c |
| ≥4000 g | 67/6272 (1.1) | 144/10,209 (1.4) | 0.058c |
| Small for gestational age, number/total number (%) | 323/6238 (5.2) | 609/10,002 (6.1) | 0.015c |
| Large for gestational age, number/total number (%) | 870/6238 (13.9) | 1456/10,002 (14.6) | 0.289c |
| Stillbirth | 30/6317 (0.5) | 48/10,283 (0.5) | 0.941c |
NC natural ovulatory cycle, HRC hormone replacement cycle
aThe data are expressed as the mean ± standard deviation
bThe differences between the groups were evaluated by the Mann-Whitney U test
cThe differences between the groups were evaluated by the chi-squared test
dThe differences between the groups were evaluated by Student’s t test