Subgroup analysis of neonatal and maternal outcomes
| n ≤16 | n 20–34 | Total valid n | Crude OR (95% CI) | aOR (95% CI)* | |
| 68 | 3951 | ||||
| Neonatal outcomes | |||||
| Low birth weight (<2500 g) | 5 | 349 | 3792 | 0.81 (0.32 to 2.02) | 0.83 (0.32 to 2.13) |
| Very low birth weight (<1500 g) | 2 | 36 | 3476 | 3.13 (0.74 to 13.29) | 3.00 (0.66 to 13.59) |
| Extremely low birth weight (<1000 g) | 1 | 10 | 3449 | 5.63 (0.71 to 44.68) | 5.90 (0.67 to 51.85) |
| Macrosomia (birth weight >4000 g) | 3 | 223 | 3664 | 0.76 (0.24 to 2.43) | 0.62 (0.19 to 2.02) |
| Small for gestational age | 6 | 576 | 3585 | 0.57 (0.24 to 1.33) | 0.74 (0.31 to 1.77) |
| Large for gestational age | 8 | 426 | 3437 | 1.03 (0.49 to 2.17) | 0.91 (0.42 to 1.95) |
| Preterm delivery (<37 weeks) | 5 | 236 | 4019 | 1.25 (0.50 to 3.14) | 1.08 (0.42 to 2.76) |
| Very preterm delivery (<32 weeks) | 1 | 35 | 3814 | 1.69 (0.23 to 12.49) | 1.66 (0.21 to 12.88) |
| Extremely preterm delivery (<28 weeks) | 1 | 5 | 3784 | 11.79 (1.36 to 102.41) | 6.24 (0.61 to 64.20) |
| Stillborn | 0 | 26 | 4019 | † | † |
| Apgar score <7 at 1 min | 9 | 456 | 4019 | 1.17 (0.58 to 2.37) | 1.02 (0.50 to 2.11) |
| Apgar score <7 at 5 min | 2 | 136 | 4019 | 0.85 (0.21 to 3.51) | 0.85 (0.20 to 3.60) |
| Maternal outcomes | |||||
| Pre-eclampsia | 4 | 146 | 4019 | 1.63 (0.59 to 4.53) | 1.71 (0.59 to 4.91) |
| Gestational diabetes | 0 | 264 | 4019 | † | † |
| Caesarean delivery | 6 | 990 | 4019 | 0.29 (0.13 to 0.67) | 0.31 (0.13 to 0.72) |
| Instrumental birth‡ | 14 | 706 | 3025 | 0.83 (0.46 to 1.50) | 0.87 (0.47 to 1.60) |
Reference group: maternal age 20–34 years.
*Adjusted for IMD score and ethnicity.
†No valid result available due to small numbers.
‡Vaginal deliveries only, included both forceps and ventouse deliveries.
aOR, adjusted OR; IMD, Index of multiple deprivation.