Characteristics of the study population according to gestational age at birth (n=3 427 450)
| Measure | 37+0 to 40+6 weeks | 41+0 and above | Difference (95% CI) |
| Antenatal factors | |||
| Male | 1 244 878 (50.7%) | 511 567 (52.6%) | 1.82% (1.71% to 1.94%) |
| Birth weight (g) | 3511 (473) | 3798 (474) | 288 (287 to 289) |
| Maternal pre-eclampsia | 115 578 (4.7%) | 38 693 (4.0%) | −0.07% (−0.08% to 0.07%) |
| Intrapartum factors | |||
| Maternal infection | 16 092 (0.66%) | 7240 (0.74%) | 0.09% (0.07% to 0.11%) |
| Neonatal infection | 10 334 (0.4%) | 6125 (0.6%) | 0.21% (0.19% to 0.22%) |
| Caesarean section | 294 707 (12.1%) | 85 400 (8.8%) | −3.24% (−3.31% to −3.16%) |
| Demographic factors | |||
| Maternal age | 28.1 (5.2) | 27.8 (5.1) | −0.30 (−0.31 to −0.29) |
| Primiparae | 995 171 (40.6%) | 450 385 (46.3%) | 5.72% (5.60% to 5.83%) |
| Maternal occupation | |||
| Manual | 793 546 (32.3%) | 314 211 (32.3%) | −0.06% (−0.17% to 0.05%) |
| Non-manual | 868 071 (35.4%) | 371 740 (38.2%) | 2.82% (2.70% to 2.93%) |
| Other | 792 403 (32.3%) | 287 479 (29.5%) | −2.86% (−2.87% to −2.65%) |
| Maternal education status | |||
| <9 years | 71 148 (2.9%) | 28 652 (2.9%) | 0.04% (0.04% to 0.08%) |
| 9–10 years | 919 214 (37.5%) | 364 418 (37.4%) | −0.02% (−0.01% to 0.09%) |
| Full secondary | 465 920 (19.0%) | 177 561 (18.2%) | −0.75% (−0.84% to −0.65%) |
| Higher education | 997 738 (40.7%) | 402 799 (41.4%) | 0.72% (0.61% to 0.84%) |
Values are number (per cent), mean (±SD) or difference (95% CI) as appropriate.