Table 5.
Assessment of competing risk of preterm birth for pre-eclampsia among all participants.
| PTB among no pre-eclampsia | Pre-eclampsia among no PTB | Competing risk regression for pre-eclampsia | ||||
|---|---|---|---|---|---|---|
| Adjusted models§ | Hazards ratio (95% CI) | P value | Hazards ratio (95% CI) | P value | Hazards ratio* (95% CI) | P value |
| Opioids | 1.39 (1.01, 1.90) | 0.04 | 1.69 (1.06, 2.70) | 0.03 | 1.03 (0.80, 1.34) | 0.80 |
| Cocaine | 1.34 (0.85, 2.11) | 0.20 | 0.47 (0.11, 1.97) | 0.30 | 0.76 (0.39, 1.49) | 0.43 |
| Cannabis | 1.01 (0.76, 1.34) | 0.93 | 0.79 (0.49, 1.27) | 0.33 | 1.11 (0.77, 1.61) | 0.56 |
| Alcohol | 1.04 (0.85, 1.28) | 0.68 | 0.95 (0.72, 1.27) | 0.75 | 0.87 (0.71, 1.07) | 0.19 |
| Tobacco | 1.29 (1.08, 1.54) | 0.006 | 0.81 (0.63, 1.04) | 0.10 | 0.85 (0.71, 1.02) | 0.07 |
| Polysubstance score† | 1.18 (1.08, 1.29) | <0.001 | 0.93 (0.81, 1.08) | 0.34 | 0.88 (0.80, 0.97) | 0.01 |
*
Fine-Gray subdistribution hazards model with preterm birth as the competing risk, and pre-eclampsia (mild, moderate, or severe) as the main outcome of interest. For all hazards models conducted, the gestational age was the time metric.
†
Polysubstance score was an unweighted sum of the number of substances used in order to estimate the aggregate burden of substance use in pregnancy.
§
Adjusted for maternal age, maternal pre-pregnancy BMI, yearly income, educational status, immigration history, parity, and sex of the child. Gestational age was the time metric for Cox regression. BMI, body mass index; CI, confidence interval; PTB, preterm birth.