Table 2.
Sex ratio among singleton live births stratified by different demographic characteristics and the embryo culture condition
| Characteristic | Singletons (n) | Male (n) | Sex ratio(%) | P-value |
|---|---|---|---|---|
| Blastocyst quality | <0.001 | |||
| High | 638 | 383 | 60.0 | |
| Poor | 572 | 284 | 49.7 | |
| Maternal age | 0.261 | |||
| <35 | 971 | 543 | 55.9 | |
| ≥ 35 | 239 | 124 | 51.9 | |
| Maternal BMI | 0.173 | |||
| <18.5 | 47 | 32 | 68.1 | |
| 18.5 ~ 24.9 | 772 | 425 | 55.1 | |
| ≥ 25 | 391 | 210 | 53.7 | |
| Type of infertility | 0.887 | |||
| Primary | 541 | 297 | 54.9 | |
| Secondary | 669 | 370 | 55.3 | |
| Cause of infertility | 0.537 | |||
| Female factor | 661 | 363 | 54.9 | |
| Male factor | 307 | 178 | 58 | |
| Combined factor | 193 | 102 | 52.8 | |
| Unexplained | 49 | 24 | 49 | |
| Type of fertilization | 0.191 | |||
| IVF | 855 | 461 | 53.9 | |
| ICSI | 355 | 206 | 58.0 | |
| Day of frozen embryo | 0.774 | |||
| D5 | 783 | 434 | 55.4 | |
| D6 | 427 | 233 | 54.6 |
Note: The sex ratio at birth is calculated as the proportion of males among all livebirths. P < 0.05 was considered statistically significant. CI = confidence interval; BMI = body mass index; D = day; IVF = in vitro fertilization; ICSI = intracytoplasmic sperm injection