Table 4.
Gestational-age specific association between maternal age and fetal/infant mortality
| Offspring age |
Conventional risk ratio, maternal age (95% CI)a |
Fetuses-at-risk risk ratio, maternal age (95% CI)a |
Change log (RR)b |
|||
|---|---|---|---|---|---|---|
| <20 years | ≥35 years | <20 years | ≥35 years | <20 years | ≥35 years | |
| Stillbirth, wk | ||||||
| 22–24 | 1.06 (0.90–1.25) | 0.94 (0.81–1.09) | 1.32 (1.12–1.56) | 1.43 (1.23–1.65) | 0.22 | 0.42 |
| 25–27 | 0.89 (0.70–1.13) | 1.14 (0.94–1.39) | 1.21 (0.95–1.54) | 1.69 (1.38–2.05) | 0.30 | 0.39 |
| 28–31 | 0.92 (0.75–1.13) | 1.04 (0.86–1.24) | 1.23 (1.00–1.50) | 1.50 (1.25–1.80) | 0.29 | 0.37 |
| 32–36 | 1.03 (0.88–1.21) | 1.12 (0.97–1.29) | 1.10 (0.94–1.30) | 1.41 (1.23–1.63) | 0.07 | 0.23 |
| ≥37 | 1.12 (0.98–1.28) | 1.53 (1.37–1.71) | 1.12 (0.98–1.28) | 1.53 (1.37–1.71) | 0 | 0 |
| Early neonatal, wk | ||||||
| 22–24 | 1.04 (0.96–1.12) | 0.95 (0.89–1.02) | 1.29 (1.07–1.55) | 1.40 (1.19–1.65) | 0.22 | 0.39 |
| 25–27 | 1.47 (1.15–1.89) | 0.85 (0.66–1.11) | 2.06 (1.56–2.73) | 1.14 (0.86–1.51) | 0.34 | 0.29 |
| 28–31 | 1.26 (0.90–1.76) | 0.92 (0.66–1.27) | 1.63 (1.15–2.31) | 1.14 (0.81–1.59) | 0.26 | 0.22 |
| 32–36 | 1.31 (0.99–1.75) | 1.13 (0.89–1.43) | 1.43 (1.06–1.91) | 1.37 (1.08–1.75) | 0.08 | 0.20 |
| ≥37 | 1.03 (0.83–1.29) | 1.15 (0.96–1.37) | 1.03 (0.83–1.29) | 1.15 (0.96–1.37) | 0 | 0 |
| Late neonatal, wk | ||||||
| 22–24 | 0.90 (0.51–1.61) | 1.09 (0.67–1.76) | 0.84 (0.43–1.66) | 1.92 (1.13–3.26) | −0.07 | 0.56 |
| 25–27 | 1.22 (0.72–2.06) | 1.36 (0.86–2.14) | 1.82 (1.46–2.28) | 1.30 (1.06–1.59) | 0.40 | −0.04 |
| 28–31 | 0.99 (0.46–2.12) | 1.21 (0.65–2.26) | 1.21 (0.55–2.62) | 1.52 (0.82–2.85) | 0.20 | 0.23 |
| 32–36 | 1.96 (1.14–3.36) | 1.58 (1.01–2.49) | 2.12 (1.22–3.67) | 1.90 (1.21–2.99) | 0.08 | 0.18 |
| ≥37 | 1.98 (1.48–2.64) | 0.99 (0.74–1.31) | 1.98 (1.48–2.64) | 0.99 (0.74–1.31) | 0 | 0 |
| Post neonatal, wk | ||||||
| 22–24 | 1.34 (0.60–2.98) | 1.14 (0.59–2.23) | 1.44 (0.59–3.55) | 2.00 (0.99–4.06) | 0.07 | 0.56 |
| 25–27 | 1.63 (0.96–2.78) | 0.88 (0.51–1.54) | 2.00 (1.14–3.51) | 1.21 (0.68–2.13) | 0.21 | 0.32 |
| 28–31 | 1.27 (0.70–2.28) | 0.96 (0.52–1.79) | 1.59 (0.86–2.92) | 1.22 (0.65–2.28) | 0.23 | 0.24 |
| 32–36 | 2.39 (1.78–3.19) | 0.81 (0.57–1.14) | 2.73 (2.02–3.69) | 0.97 (0.68–1.38) | 0.13 | 0.19 |
| ≥37 | 3.75 (3.27–4.30) | 1.02 (0.87–1.20) | 3.75 (3.27–4.30) | 1.02 (0.87–1.20) | 0 | 0 |
aRelative to maternal age 25–29 years (stillbirth) and 30–34 years (early, late and post neonatal mortality), adjusted for marital status, parity, region and period; other age categories not shown, to conserve space.
bFetuses-at-risk log(risk ratio) minus conventional log(risk ratio).