Table 3.
Multivariate-adjusted Interaction Between Maternal Smoking and Preeclampsia on the Risk of Preterm Delivery Before 37 Weeks’ Gestation in 674,250 Singleton Pregnancies in New York City Between 1995 and 2003
| Level of Smoking by Preeclampsia Interaction | Total Preeclampsia Cases | Isolated Preeclampsia | Chronic Hypertension With Preeclampsia | |||
| aORa | 95% CI | aORa | 95% CI | aORa | 95% CI | |
| Nonsmoker and no preeclampsia | 1.00 | 1.00 | 1.00 | |||
| Smoker only | 1.76 | 1.69, 1.82 | 1.75 | 1.69, 1.82 | 1.73 | 1.67, 1.94 |
| Preeclampsia only | 4.59 | 4.30, 4.57 | 4.13 | 4.00, 4.27 | 7.94 | 7.40, 8.53 |
| Smoker and preeclampsiab | 3.99 | 3.46, 4.59 | 3.46 | 2.94, 4.08 | 6.22 | 4.67, 8.30 |
Abbreviations: aOR, adjusted odds ratio; CI, confidence interval.
a
The multivariate model included race/ethnicity, maternal age, maternal smoking, maternal education, parity, preeclampsia subtype, prepregnancy weight, year of birth, presence of gestational diabetes, and smoking-by-preeclampsia-subtype product term.
b
The 1-df Wald chi-square interaction P values: all preeclampsia (P < 0.001), isolated preeclampsia (P < 0.001), and chronic hypertension with preeclampsia (P < 0.001).