Associations of quartiles of factor scores, characterised by occupational physical activity and psychosocial stressors, and preterm birth (PTB) and small-for-gestational-age (SGA) in the first trimester of pregnancy, National Birth Defects Prevention Study, 1997–2009
| Factor* | PTB | SGA | ||
|---|---|---|---|---|
| Crude OR (95% CI) | Adjusted† OR (95% CI) | Crude OR (95% CI) | Adjusted† OR (95% CI) | |
| Occupational physical activity | ||||
| Q1 | Referent | Referent | Referent | Referent |
| Q2 | 1.00 (0.75 to 1.32) | 1.00 (0.76 to 1.33) | 1.09 (0.81 to 1.46) | 1.09 (0.81 to 1.46) |
| Q3 | 1.23 (0.94 to 1.61) | 1.12 (0.85 to 1.49) | 1.31 (0.99 to 1.74) | 1.18 (0.88 to 1.58) |
| Q4 | 1.37 (1.05 to 1.79) | 1.24 (0.93 to 1.64) | 1.52 (1.15 to 2.00) | 1.36 (1.02 to 1.82) |
| ptrend | 0.01 | 0.001 | ||
| Interpersonal stressor | ||||
| Q1 | Referent | Referent | Referent | Referent |
| Q2 | 0.92 (0.70 to 1.22) | 0.98 (0.74 to 1.30) | 1.02 (0.78 to 1.33) | 1.09 (0.83 to 1.43) |
| Q3 | 1.14 (0.87 to 1.48) | 1.18 (0.90 to 1.54) | 0.80 (0.60 to 1.05) | 0.86 (0.65 to 1.14) |
| Q4 | 1.14 (0.88 to 1.49) | 1.17 (0.89 to 1.53) | 1.02 (0.79 to 1.33) | 1.05 (0.80 to 1.37) |
| ptrend | 0.15 | 0.70 | ||
| Automated work | ||||
| Q1 | Referent | Referent | Referent | Referent |
| Q2 | 0.96 (0.73 to 1.27) | 0.93 (0.71 to 1.23) | 1.08 (0.81 to 1.44) | 1.03 (0.77 to 1.38) |
| Q3 | 1.02 (0.78 to 1.34) | 0.93 (0.71 to 1.23) | 1.28 (0.97 to 1.69) | 1.12 (0.84 to 1.49) |
| Q4 | 1.12 (0.87 to 1.46) | 1.03 (0.78 to 1.34) | 1.32 (1.00 to 1.75) | 1.16 (0.87 to 1.55) |
| ptrend | 0.32 | 0.02 | ||
| Job responsibility | ||||
| Q1 | Referent | Referent | Referent | Referent |
| Q2 | 0.82 (0.63 to 1.07) | 0.92 (0.70 to 1.22) | 0.77 (0.58 to 1.01) | 0.86 (0.65 to 1.14) |
| Q3 | 0.77 (0.59 to 1.02) | 0.82 (0.62 to 1.08) | 0.88 (0.68 to 1.13) | 0.94 (0.72 to 1.23) |
| Q4 | 0.99 (0.77 to 1.27) | 1.16 (0.88 to 1.53) | 0.72 (0.55 to 0.95) | 0.85 (0.63 to 1.15) |
| ptrend | 0.92 | 0.05 | ||
*Factor scores were categorised in quartiles: ‘occupational physical activity’ (<−0.88, −0.88 to <0.05, 0.05 to <0.91 and ≥0.91), ‘interpersonal stressor’ (<−0.39, −0.39 to <0.16, 0.16 to <0.65 and ≥0.65), ‘automated work’ (<−0.77, −0.77 to <−0.05, −0.05 to <0.50 and ≥0.50) and ‘job responsibility’ (<−0.69, −0.69 to <−0.11, −0.11 to <0.46 and ≥0.46).
†Adjusted for maternal age, race/ethnicity, education and smoking.