Table 5. Absolute risk difference of adverse birth outcomes in relation to maternal age by log-binomial model.
| absolute risk difference (95% CI) | ||||
| Maternal age (y) | Composite † | Stillbirth † | Preterm birth ‡ | Low birth weight ‡ |
| ≤14 | 1.35 (1.14–1.56)* | 2.64 (2.38–2.91)* | 1.58 (1.32–1.84)* | 1.58 (1.31–1.86)* |
| 15 | 0.93 (0.80–1.06)* | 1.96 (1.75–2.18)* | 1.16 (0.99–1.33)* | 1.09 (0.90–1.27)* |
| 16 | 0.71 (0.62–0.79)* | 1.44 (1.26–1.61)* | 0.78 (0.66–0.90)* | 0.90 (0.78–1.03)* |
| 17 | 0.63 (0.56–0.69)* | 0.90 (0.73–1.06)* | 0.65 (0.56–0.75)* | 0.94 (0.85–1.04)* |
| 18 | 0.44 (0.39–0.49)* | 0.66 (0.52–0.81)* | 0.49 (0.41–0.57)* | 0.75 (0.67–0.83)* |
| 19 | 0.32 (0.28–0.36)* | 0.38 (0.26–0.50)* | 0.30 (0.23–0.36)* | 0.53 (0.47–0.59)* |
| 20 | 0.22 (0.18–0.25)* | 0.17 (0.06–0.29)* | 0.21 (0.15–0.26)* | 0.39 (0.34–0.45)* |
| 21 | 0.17 (0.14–0.20)* | 0.17 (0.06–0.27)* | 0.13 (0.08–0.18)* | 0.34 (0.29–0.39)* |
| 22 | 0.10 (0.07–0.13)* | 0.00 (−0.10–0.10) | 0.07 (0.02–0.12)* | 0.22 (0.17–0.26)* |
| 23 | 0.07 (0.04–0.10)* | 0.01 (−0.09–0.10) | 0.03 (−0.02–0.07) | 0.15 (0.11–0.20)* |
| 24 | 0.03 (0.01–0.06)* | 0.02 (−0.06–0.11) | 0.03 (−0.01–0.07) | 0.12 (0.07–0.16)* |
| 25 | 0.03 (0.01–0.06)* | 0.01 (−0.08–0.09) | 0.01 (−0.03–0.05) | 0.09 (0.05–0.13)* |
| 26 | 0.02 (−0.00–0.05) | 0.00 (−0.08–0.09) | 0.00 (−0.03–0.04) | 0.07 (0.03–0.11)* |
| 27 | 0 | 0 | 0 | 0 |
| 28 | 0.00 (−0.02–0.02) | 0.04 (−0.03–0.12) | 0.01 (−0.03–0.04) | 0.02 (−0.02–0.06) |
| 29 | 0.01 (−0.01–0.03) | 0.08 (0.00–0.16)* | 0.06 (0.02–0.09)* | 0.02 (−0.02–0.06) |
| 30 | 0.01 (−0.01–0.04) | 0.08 (0.00–0.16)* | 0.04 (0.01–0.08)* | 0.02 (−0.02–0.06) |
| 31 | 0.03 (0.01–0.05)* | 0.18 (0.10–0.26)* | 0.06 (0.03–0.10)* | 0.01 (−0.03–0.05) |
| 32 | 0.06 (0.04–0.08)* | 0.24 (0.16–0.32)* | 0.11 (0.08–0.15)* | 0.03 (−0.01–0.07) |
| 33 | 0.07 (0.05–0.10)* | 0.26 (0.18–0.35)* | 0.14 (0.10–0.17)* | 0.04 (−0.00–0.08) |
| 34 | 0.13 (0.10–0.15)* | 0.45 (0.37–0.53)* | 0.19 (0.15–0.23)* | 0.10 (0.06–0.15)* |
| 35 | 0.18 (0.15–0.20)* | 0.55 (0.46–0.64)* | 0.27 (0.23–0.31)* | 0.11 (0.07–0.16)* |
| 36 | 0.23 (0.20–0.25)* | 0.65 (0.56–0.74)* | 0.34 (0.30–0.39)* | 0.16 (0.11–0.21)* |
| 37 | 0.27 (0.24–0.31)* | 0.75 (0.65–0.84)* | 0.39 (0.34–0.43)* | 0.21 (0.15–0.27)* |
| 38 | 0.33 (0.29–0.36)* | 0.76 (0.66–0.87)* | 0.48 (0.43–0.53)* | 0.27 (0.21–0.33)* |
| 39 | 0.33 (0.29–0.37)* | 1.01 (0.90–1.13)* | 0.49 (0.42–0.55)* | 0.35 (0.28–0.42)* |
| 40 | 0.35 (0.30–0.40)* | 1.06 (0.93–1.19)* | 0.52 (0.45–0.60)* | 0.35 (0.27–0.44)* |
| 41 | 0.46 (0.40–0.52)* | 1.25 (1.09–1.40)* | 0.71 (0.63–0.80)* | 0.44 (0.33–0.54)* |
| 42 | 0.52 (0.44–0.60)* | 1.34 (1.15–1.53)* | 0.77 (0.66–0.88)* | 0.56 (0.43–0.69)* |
| 43 | 0.62(0.52–0.73)* | 1.56 (1.33–1.78)* | 0.88 (0.74–1.01)* | 0.65 (0.49–0.81)* |
| ≥44 | 0.83 (0.72–0.93)* | 1.77 (1.56–1.98)* | 0.94 (0.80–1.08)* | 0.73 (0.57–0.90)* |
Reference year of maternal age: 27.
* p<0.05.
n = 2,123,751 births;
n = 2,045,748 singleton live births. Covariates: (1) composite adverse birth outcome (at least one of stillbirth, preterm birth, low birth weight, congenital anomaly, macrosomia, neonatal death, and SGA): pregnancy-related disorders, obstetric complications, ethnicity, birth region, birth year, parity, sex at birth, Apgar score, and delivery mode; (2) stillbirth: pregnancy-related disorders, obstetric complications, ethnicity, birth region, birth year, sex at birth, parity, congenital anomalies, neonatal death, Apgar score, delivery mode, gestational age, and birth weight; (3) preterm birth: pregnancy-related disorders, obstetric complications, ethnicity, birth region, birth year, sex at birth, parity, congenital anomalies, neonatal death, Apgar score, delivery mode, and birth weight; (4) low birth weight: pregnancy-related disorders, obstetric complications, ethnicity, birth region, birth year, sex at birth, parity, congenital anomalies, neonatal death, Apgar score, delivery mode, and gestational age.