Association between weekly working hours and pregnancy outcomes in subgroup of pregnant women with paid employment†
| Pregnancy outcomes | n | OR for adverse pregnancy outcome (95% CI) | p For trend | ||
| 1–24 h (n=1136) | 25–39 h (n=2216) | 40 h or more (n=1056) | |||
| Pregnancy-induced hypertension | 4327 | Reference | 0.86 (0.57 to 1.30) | 0.76 (0.47 to 1.24) | 0.875 |
| Pre-eclampsia | 4327 | Reference | 0.90 (0.51 to 1.61) | 0.96 (0.50 to 1.84) | 0.938 |
| Gestational diabetes | 4263 | Reference | 1.59 (0.78 to 3.25) | 1.74 (0.69 to 4.38) | 0.210 |
| Preterm ruptured membranes | 4255 | Reference | 1.19 (0.74 to 1.91) | 1.35 (0.79 to 2.31) | 0.278 |
| Poor progress of delivery | 4253 | Reference | 0.89 (0.71 to 1.12) | 0.83 (0.64 to 1.08) | 0.174 |
| Mode of delivery | 4042 | ||||
| Assisted vaginal delivery‡ | Reference | 0.98 (0.77 to 1.25) | 0.98 (0.75 to 1.29) | 0.916 | |
| Elective caesarean delivery‡ | Reference | 1.03 (0.70 to 1.50) | 1.06 (0.68 to 1.66) | 0.796 | |
| Emergency caesarean delivery‡ | Reference | 0.95 (0.69 to 1.31) | 0.76 (0.52 to 1.11) | 0.126 | |
| Preterm birth (<37 weeks) | 4408 | Reference | 1.37 (0.91 to 2.06) | 1.30 (0.81 to 2.10) | 0.345 |
| Meconium-stained amniotic fluid (yes) | 4214 | Reference | 1.00 (0.80 to 1.25) | 1.12 (0.86 to 1.46) | 0.399 |
| Apgar score at 5 min (<7) | 4269 | Reference | 0.62 (0.27 to 1.41) | 0.94 (0.38 to 2.35) | 0.982 |
| Small-for-gestational-age (<10th percentile) | 4403 | Reference | 0.95 (0.72 to 1.25) | 1.01 (0.73 to 1.39) | 0.924 |
| Difference between weekly working hours categories (95% CI) | |||||
| Birth weight (g) | 4405 | Reference | −21 (−56 to 15) | −45 (−89 to −1)* | 0.044 |
↵* p<0.05.
↵† Adjusted for pregnant women's age, parity, educational level, family income, ethnicity, marital status, psychopathological symptoms, smoking and drinking during pregnancy, body mass index (BMI) and offspring's gender. The analyses for birth weight were additionally adjusted for gestational age at birth.
↵‡ Compared to spontaneous vaginal delivery.