Table 2. Prevalence of smoking during pregnancy, and risk ratios (RRs) and relative excess incidence proportions (REIs) for obstetric complications.
|
Smoking prevalence |
Crude RR (95% CI) |
Age-adjusted RR (95% CI) |
Age-adjusted REIa (95% CI) |
|
| Control cohort | 5.8% | |||
| Cases of obstetric complications | ||||
| Threatened premature deliveryb | 8.0% | 1.42 (1.20–1.68) | 1.38 (1.17–1.64) | 27.7% (14.5%–38.9%) |
| Incompetent cervix | 8.8% | 1.58 (1.31–1.90) | 1.63 (1.35–1.96) | 38.5% (25.8%–49.1%) |
| Pregnancy-induced hypertension | 6.5% | 1.14 (0.97–1.35) | 1.20 (1.01–1.41) | 16.4% (1.2%–29.3%) |
| Eclampsia | 4.9% | 0.84 (0.39–1.82) | 0.82 (0.38–1.78) | |
| Pulmonary edema | 6.6% | 1.15 (0.46–2.88) | 1.22 (0.49–3.06) | |
| Placental abruption | 7.6% | 1.34 (1.07–1.67) | 1.37 (1.10–1.72) | 27.1% (8.8%–41.7%) |
| Placenta previa | 5.6% | 0.97 (0.77–1.21) | 1.07 (0.85–1.34) | |
| Preterm PROMb | 9.3% | 1.68 (1.43–1.97) | 1.67 (1.43–1.96) | 40.2% (29.9%–49.1%) |
| Chorioamnionitis | 9.3% | 1.68 (1.38–2.03) | 1.65 (1.36–2.00) | 39.4% (26.4%–50.0%) |
| Placenta accreta | 7.9% | 1.41 (0.83–2.39) | 1.52 (0.89–2.59) | |
| DIC syndrome | 7.3% | 1.29 (0.84–1.98) | 1.35 (0.88–2.08) |
CI: confidence interval; DIC: disseminated intravascular coagulation; PROM: premature rupture of the membranes.
aREI was calculated for obstetric complications significantly associated with maternal smoking during pregnancy.
bBefore 37 weeks of pregnancy.