| Maternal age at birth (mean) |
| 31.2 ± 5.01 |
| Paternal age at birth (mean) |
| 32.9 ± 5.76 |
| Maternal years of education (mean) |
| 13.8 ± 1.92 |
| Paternal years of education (mean) |
| 14.1 ± 2.65 |
| Marital status at early pregnancy | Married | 747 (97.1%) |
| Annual household income | Unmarried | 22 (2.9%) |
| ≥8 million yen | 151 (19.6%) | |
| 3 - 7.9 million yen | 566 (73.6%) | |
| <3 million yen | 52 (6.8%) | |
| Maternal history of depression and/or anxiety disorder | No | 679 (88.3%) |
| Yes | 90 (11.7%) | |
| Infant gender | Female | 383 (49.8%) |
| Male | 386 (50.2%) |