Variables | No injury n=5898 n(%) | Injury n=406 n(%) | Model 1 Unadjusted IRR (95% CI) | Model 2 Adjusted IRR (95% CI) | Model 3 Adjusted IRR (95% CI) With interaction | |
Demographics | ||||||
Gender | Female | 2852 (93.9) | 184 (6.1) | 1 | 1 | 1 |
Male | 3046 (93.2) | 222 (6.8) | 1.12 (0.93 to 1.35) | 1.17 (0.95 to 1.44) | 1.19 (0.96 to 1.46) | |
Maternal age | <25 years | 1069 (91.1) | 105 (8.9) | 1.63 (1.24 to 2.15) | 1.40 (1.01 to 1.99) | 1.54 (1.20 to 2.16) |
25 to 34 years | 3310 (93.9) | 213 (6.1) | 1.10 (0.87 to 1.40) | 1.18 (0.87 to 1.48) | 1.17 (0.88 to 1.53) | |
≥ 35 years | 1518 (94.5) | 88 (5.5) | 1 | |||
Maternal education level | No secondary school | 375 (90.1) | 41 (9.9) | 1.54 (1.06 to 2.23) | 0.68 (0.41 to 1.13) | 0.63 (0.38 to 1.04) |
Secondary school | 1381 (93.9) | 89 (6.1) | 0.94 (0.69 to 1.29) | 0.66 (0.46 to 0.97) | 0.63 (0.43 to 0.92) | |
Diploma/Trade | 1814 (93.6) | 123 (6.4) | 0.99 (0.74 to 1.32) | 0.72 (0.51 to 1.03) | 0.71 (0.50 to 1.00) | |
Bachelors degree | 1362 (93.9) | 88 (6.1) | 0.95 (0.69 to 1.29) | 0.89 (0.64 to 1.26) | 0.85 (0.63 to 1.25) | |
Higher degree | 947 (93.6) | 65 (6.4) | 1 | 1 | 1 | |
Maternal ethnicity | European | 3240 (94.1) | 203 (5.9) | 1 | 1 | 1 |
Māori | 775 (91.4) | 73 (8.6) | 1.50 (1.13 to 1.89) | 1.22 (0.90 to 1.64) | 1.17 (0.87 to 1.59) | |
Pacific | 786 (90.7) | 80 (9.3) | 1.57 (1.22 to 2.01) | 1.12 (0.80 to 1.56) | 1.12 (0.80 to 1.56) | |
Asian | 877 (96.1) | 36 (3.9) | 0.64 (0.45 to 0.92) | 0.66 (0.45 to 0.99) | 0.67 (0.45 to 0.99) | |
Others | 202 (93.5) | 14 (6.5) | 1.09 (0.62 to 1.90) | 0.89 (0.64 to 1.26) | 0.81 (0.42 to 1.58) | |
Early childhood factors | ||||||
Birth complications for baby* | No | 748 (92.9) | 57 (7.1) | 1 | – | – |
Yes | 5018 (93.6) | 342 (6.4) | 0.90 (0.69 to 1.18) | |||
Gestational age | Preterm | 294 (95.2) | 15 (4.9) | 1 | ||
Term | 5448 (93.5) | 380 (6.5) | 1.34 (0.81 to 2.22) | – | – | |
Post-term | 146 (93.6) | 10 (6.4) | 1.32 (0.61 to 2.87) | – | – | |
Birth weight | Low | 202 (92.2) | 17 (7.8) | 1.314 (0.75 to 2.29) | – | – |
Normal | 4693 (93.5) | 325 (6.5) | 1.081 (0.82 to 1.43) | |||
High | 999 (94.0) | 64 (6.0) | 1 | |||
Maternal well-being | ||||||
Smoking status during pregnancy | Current smoker | 507 (89.3) | 61 (10.7) | 1.94 (1.48 to 2.54) | 1.36 (1.10 to 1.85) | 1.50 (1.08 to 1.06) |
Former smoker | 518 (92.5) | 42 (7.5) | 1.42 (1.03 to 1.94) | 1.20 (0.85 to 1.68) | 1.15 (0.82 to 1.63) | |
Non-smoker | 4379 (94.6) | 248 (5.4) | 1 | 1 | 1 | |
Maternal health | Poor to fair | 551 (89.4) | 65 (10.6) | 1.76 (1.37 to 2.26) | – | – |
Good to excellent | 5333 (94.0) | 341 (6.0) | 1 | |||
Maternal stress score† | 13.01 (6.4) | 14.59 (6.3) | 1.04 (1.02 to 1.05) | – | – | |
Maternal depression‡ | No | 4526 (94.33) | 272 (5.67) | 1.46 (1.14 to 1.86) | 1.03 (1.01 to 1.05) | 1.05 (0.79 to 1.41) |
Yes | 823 (91.75) | 74 (8.25) | 1 | 1 | 1 | |
Relationship status | Single | 262 (89.4) | 31 (10.6) | 1.73 (1.20 to 2.48) | 1.19 (0.79 to 1.80) | 0.90 (0.52 to 1.57) |
With partner | 5145 (94.1) | 322 (5.9) | 1 | 1 | 1 | |
Socioeconomic status | ||||||
Employment status | Employed | 2391 (93.0) | 180 (7.0) | 1 | 1 | 1 |
Not employed | 3314 (94.2) | 203 (5.8) | 1.19 (0.98 to 1.45) | 1.13 (0.91 to 1.41) | 0.90 (0.72 to 1.13) | |
Family stress | 10.56 (4.2) | 11.10 (4.0) | 1.03 (1.00 to 1.05) | 1.01 (0.98 to 1.03) | – | |
Household Income tested benefit | No | 4966 (94.2) | 305 (5.8) | 1.64 (1.16 to 2.34) | – | – |
Yes | 294 (90.5) | 31 (9.5) | 1 | – | ||
Deprivation index | Low (1-3) | 1518 (94.6) | 86 (5.4) | 1 | 1 | 1 |
Medium (4-7) | 2214 (94.6) | 127 (5.4) | 1.01 (0.78 to 1.32) | 1.08 (0.80 to 1.44) | 1.07 (0.80 to 1.43) | |
High (8-10) | 2162 (91.8) | 193 (8.2) | 1.52 (1.20 to 1.95) | 1.38 (1.02 to 1.87) | 1.35 (1.00 to 1.82) | |
Dwelling | Ownership | 2865 (94.4) | 169 (5.6) | 1 | 1 | 1 |
Private rental | 2065 (93.9) | 135 (6.1) | 1.10 (0.89 to 1.37) | 0.98 (0.66 to 1.45) | 0.96 (0.65 to 1.21) | |
Public rental | 382 (91.4) | 36 (8.6) | 1.55 (1.10 to 2.18) | 0.98 (0.78 to 1.23) | 0.96 (0.76 to 1.43) | |
Interaction effect | With partnerwith no maternal depression | – | – | – | 1 | |
Single parent with depression | 2.20 (1.04 to 4.64) | |||||
Deviance goodness-of-fit | 1846.1 (p=1.000) | 1840(p=1.000) | ||||
Pearson goodness-of-fit | 5317.57 (p=0.995) | 5301.1(p=0.995) |
Significant factors are in bold.
*admission to neonatal intensive care, hypoglycaemia, infections, jaundice, meconium aspiration, breathing difficulties and distress, and the use of a ventilator captured during the 16 month data collection wave.
†maternal stress score = Perceived stress anxiety.
‡maternal depression score=Edinburgh Postnatal Depression Scale20 (10-item questions total score=30).
1, reference group; IRR, incidence Risk Ratio; NCEA, National Certificate of Educational Achievement.