Table 3.
Associations between parity/maternal age and adverse birth outcomes (adjusted RR and 95% CI)
| Adverse birth outcomes | Maternal age (y) | |||
|---|---|---|---|---|
| < 25 | 25–29 | 30–34 | ≥35 | |
| PTB | ||||
| Nulliparity | 0.94 (0.90, 0.97) | 1.0 (ref) | 1.20 (1.15, 1.25) | 1.63 (1.51, 1.76) |
| Multiparity | 0.94 (0.88, 1.00) | 0.96 (0.92, 0.99) | 1.05 (1.01, 1.09) | 1.39 (1.32, 1.45) |
| LBW | ||||
| Nulliparity | 1.06 (1.02, 1.10) | 1.0 (ref) | 1.27 (1.21, 1.34) | 1.56 (1.41, 1.73) |
| Multiparity | 0.86 (0.79, 0.93) | 0.81 (0.78, 0.85) | 0.84 (0.80, 0.88) | 1.14 (1.07, 1.21) |
| SGA | ||||
| Nulliparity | 1.14 (1.11, 1.17) | 1.0 (ref) | 1.04 (1.01, 1.08) | 1.13 (1.04, 1.22) |
| Multiparity | 0.88 (0.84, 0.93) | 0.68 (0.66, 0.70) | 0.63 (0.61, 0.65) | 0.73 (0.70, 0.77) |
PTB was defined as gestational age < 37 weeks, LBW was defined as birth weight < 2500 g; SGA was defined as birth weight below 10th centile for specific gestational age and sex
Reference group: Nulliparity/aged between 25 and 29 years
Adjusted for maternal race, area of residence, immigrant status, education, pre-pregnancy obesity, paternal age and race, and sex of newborn
Abbreviations: PTB Preterm Birth, LBW Low Birth Weight, SGA Small for Gestational Age