Table 1.
Characteristics of study populations
| Male infants (n = 60028) | Female infants (n = 49694) | Ratio | P | |
|---|---|---|---|---|
| n (%) | n (%) | |||
| Maternal age (years) | 28 (25–31) | 28 (25–31) | 0.48 | |
| ≤24 | 13894 (23.3%) | 11371 (23.0%) | 1.22 | 0.24 |
| 25-34 | 39532 (66.4%) | 33249 (67.4%) | 1.19 | <0.001 |
| ≥35 | 6105 (10.3%) | 4736 (9.6%) | 1.29 | <0.001 |
| Gravidity | 2 (1–2) | 1 (1–2) | - | <0.001 |
| Parity | 1 (1–1) | 1 (1–1) | - | <0.001 |
| Obesity | 8361 (17.1%) | 7109 (17.2%) | 1.18 | 0.07 |
| Primiparous | 48176 (80.3%) | 41130 (82.8%) | 1.17 | <0.001 |
835 missing cases for maternal ages; 19578 missing cases for maternal weight and height.
Quantitative variables are expressed as median (25th percentile–75th percentile).