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Table 3 Estimates of risk of preterm birth (spontaneous and indicated, combined)a

From: Timing and severity of COVID-19 during pregnancy and risk of preterm birth in the International Registry of Coronavirus Exposure in Pregnancy

 

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)

  1. 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
  2. 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)
  3. cOdds ratios
  4. dSevere vs. negative
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