Table 3.
Estimates of risk of preterm birth (spontaneous and indicated, combined)a
| Risk ratiosb | Standardized risksb | |||||
|---|---|---|---|---|---|---|
| Model | Positive vs. negative | Severe vs. mild/moderate | Negative | Positive | Mild/moderate | Severe |
| Log-linear regression | 1.3 (1.0, 1.7) | 2.4 (1.7, 3.3) | ||||
| Multinomial regression (Indicated)c | 2.1 (1.2, 3.7) | 4.6 (2.3, 9.3) | ||||
| Multinomial regression (Spontaneous)c | 1.1 (0.7, 1.6) | 2.6 (1.4, 4.8) | ||||
| Case-time-controlc | 1.2 (0.6, 2.3) | 2.1 (0.4, 12.1)d | ||||
| Gestational-age-specific | ||||||
| Week 20 | 1.0 (0.8, 1.2) | 1.0 (0.7, 1.4) | 9.8% (9.1, 10.5) | 10.0% (7.8, 12.0) | 10.0% (7.8, 12.0) | 9.6% (6.2, 14.0) |
| Week 21 | 1.0 (0.8, 1.2) | 1.0 (0.8, 1.5) | 9.8% (9.1, 10.5) | 9.9% (7.8, 12.0) | 9.9% (7.8, 11.9) | 10.2% (6.9, 14.2) |
| Week 22 | 1.0 (0.8, 1.3) | 1.1 (0.8, 1.5) | 9.8% (9.1, 10.5) | 10.0% (7.9, 12.3) | 9.9% (7.8, 12.2) | 11.0% (7.5, 15.3) |
| Week 23 | 1.0 (0.8, 1.3) | 1.2 (0.9, 1.6) | 9.7% (9.1, 10.4) | 10.2% (8.0, 12.8) | 10.1% (7.9, 12.7) | 12.1% (8.4, 16.7) |
| Week 24 | 1.1 (0.8, 1.4) | 1.3 (1.0, 1.7) | 9.7% (9.0, 10.4) | 10.5% (8.3, 13.3) | 10.4% (8.1, 13.0) | 13.3% (9.3, 18.5) |
| Week 25 | 1.1 (0.9, 1.4) | 1.4 (1.1, 1.8) | 9.7% (9.0, 10.3) | 10.9% (8.7, 13.5) | 10.7% (8.6, 13.1) | 14.8% (10.7, 19.9) |
| Week 26 | 1.2 (0.9, 1.4) | 1.5 (1.2, 1.9) | 9.6% (9.0, 10.3) | 11.3% (9.1, 13.6) | 11.0% (9.0, 13.3) | 16.4% (12.1, 21.7) |
| Week 27 | 1.2 (1.0, 1.5) | 1.6 (1.3, 2.0) | 9.6% (8.9, 10.3) | 11.7% (9.6, 13.9) | 11.3% (9.2, 13.5) | 18.1% (13.3, 23.6) |
| Week 28 | 1.3 (1.0, 1.5) | 1.7 (1.3, 2.2) | 9.5% (8.8, 10.2) | 12.0% (10.0, 14.1) | 11.5% (9.6, 13.5) | 19.8% (14.5, 25.5) |
| Week 29 | 1.3 (1.1, 1.5) | 1.9 (1.4, 2.4) | 9.4% (8.8, 10.1) | 12.1% (10.1, 14.1) | 11.5% (9.7, 13.4) | 21.4% (15.7, 27.2) |
| Week 30 | 1.3 (1.1, 1.5) | 2.0 (1.5, 2.6) | 9.3% (8.7, 10.0) | 12.0% (10.1, 13.9) | 11.4% (9.6, 13.2) | 22.6% (16.7, 29.2) |
| Week 31 | 1.3 (1.1, 1.5) | 2.1 (1.6, 2.8) | 9.1% (8.5, 9.8) | 11.7% (9.9, 13.6) | 11.0% (9.2, 12.8) | 23.5% (17.3, 30.4) |
| Week 32 | 1.3 (1.1, 1.5) | 2.3 (1.7, 3.0) | 8.9% (8.3, 9.5) | 11.2% (9.4, 13.0) | 10.4% (8.7, 12.1) | 23.9% (17.5, 31.3) |
| Week 33 | 1.2 (1.0, 1.4) | 2.5 (1.8, 3.3) | 8.5% (8.0, 9.1) | 10.4% (8.7, 12.0) | 9.6% (8.1, 11.2) | 23.6% (17.1, 31.4) |
| Week 34 | 1.2 (1.0, 1.4) | 2.6 (1.9, 3.6) | 7.9% (7.4, 8.4) | 9.3% (7.9, 10.7) | 8.5% (7.1, 9.8) | 22.4% (16.0, 30.2) |
| Week 35 | 1.1 (0.9, 1.3) | 2.8 (2.0, 4.0) | 6.9% (6.4, 7.3) | 7.6% (6.5, 8.8) | 6.9% (5.9, 8.0) | 19.6% (13.8, 26.6) |
| Week 36 | 1.0 (0.9, 1.2) | 3.1 (2.1, 4.5) | 4.8% (4.4, 5.1) | 4.9% (4.2, 5.7) | 4.4% (3.7, 5.1) | 13.6% (9.4, 19.4) |
aEstimates of risk of preterm birth from the various models and comparisons across levels of COVID-19. Gestational age-specific results (standardized risks and risk ratios estimated from the time-to-delivery models) are presented by week of COVID-19. Confidence intervals for the regression models were estimated with robust standard errors, and with the bootstrap for the gestational-age-specific risks and risk ratios
bAdjusted for continent (Africa, Asia, Europe, North America, South America), maternal age (years), pre-pregnancy BMI (kg/m2), parity (primi-/multiparous), race/ethnicity (Asian, Black, Latina, White, mixed, other), pre-existing condition (chronic diabetes, asthma, cardiovascular disease, or autoimmune disease), healthcare coverage (yes/no), and reason for testing (symptoms, contact tracing, surveillance, other/not tested)
cOdds ratios
dSevere vs. negative