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Table 3 Associations of exposure to the COVID-19 lockdown with preterm birth

From: Associations of COVID-19 lockdown with gestational length and preterm birth in China

 

Unexposed group (n, %)

Exposed group (n, %) a

OR for PTB (95%CI)

Term birth

PTB

Term birth

PTB

MPTB + VPTB

MPTB

VPTB

MPTB + VPTB

MPTB

VPTB

MPTB + VPTB

MPTB

VPTB

Crude OR

Adjusted OR *

Crude OR

Adjusted OR *

Crude OR

Adjusted OR *

Gestational week at the beginning of the Level I lockdown

 All

451,284 (94.7)

25,631 (5.3)

23,510 (4.9)

2121 (0.4)

92,669 (94.3)

5593 (5.7)

5150 (5.2)

443 (0.5)

1.06 (1.03, 1.09)

1.08 (1.05, 1.11)

1.07 (1.03, 1.10)

1.09 (1.05, 1.12)

1.02 (0.92, 1.13)

1.04 (0.94, 1.16)

 Conception during the lockdown

61,117 (94.5)

3528 (5.5)

3171 (4.9)

357 (0.6)

10,682 (94.4)

635 (5.6)

573 (5.1)

62 (0.5)

1.03 (0.94, 1.12)

1.09 (0.99, 1.20)

1.03 (0.94, 1.13)

1.08 (0.98, 1.19)

0.99 (0.76, 1.30)

1.20 (0.90, 1.61)

 Prior to 4th

50,272 (94.3)

3028 (5.7)

2746 (5.2)

282 (0.5)

10,295 (94.1)

642 (5.9)

591 (5.4)

51 (0.5)

1.04 (0.95, 1.13)

1.18 (1.08, 1.29)

1.05 (0.96, 1.15)

1.20 (1.09, 1.32)

0.88 (0.65, 1.19)

0.97 (0.71, 1.32)

 4th -7th

48,023 (94.3)

2950 (5.7)

2671 (5.2)

279 (0.5)

9821 (93.6)

673 (6.4)

613 (5.8)

60 (0.6)

1.12 (1.02, 1.22)

1.12 (1.03, 1.22)

1.12 (1.03, 1.23)

1.13 (1.03, 1.24)

1.05 (0.79, 1.39)

1.07 (0.81, 1.42)

 8th -11th

46,128 (94.3)

2798 (5.7)

2544 (5.2)

254 (0.5)

9581 (93.6)

656 (6.4)

597 (5.8)

59 (0.6)

1.13 (1.03, 1.23)

1.14 (1.04, 1.24)

1.13 (1.03, 1.24)

1.14 (1.04, 1.25)

1.12 (0.84, 1.49)

1.13 (0.85, 1.51)

 12th -15th

43,652 (94.4)

2603 (5.6)

2356 (5.1)

247 (0.5)

9236 (93.9)

608 (6.1)

546 (5.5)

62 (0.6)

1.10 (1.01, 1.21)

1.11 (1.02, 1.22)

1.10 (1.00, 1.21)

1.10 (1.00, 1.21)

1.19 (0.90, 1.57)

1.21 (0.91, 1.59)

 16th -19th

43,439 (94.6)

2474 (5.4)

2252 (4.9)

222 (0.5)

8966 (94.0)

573 (6.0)

524 (5.5)

49 (0.5)

1.12 (1.02, 1.23)

1.14 (1.04, 1.25)

1.13 (1.02, 1.24)

1.14 (1.04, 1.26)

1.07 (0.78, 1.46)

1.11 (0.82, 1.52)

 20th -23rd

38,806 (94.6)

2211 (5.4)

2011 (4.9)

200 (0.5)

8281 (93.8)

549 (6.2)

502 (5.7)

47 (0.5)

1.16 (1.06, 1.28)

1.19 (1.08, 1.31)

1.17 (1.06, 1.29)

1.19 (1.08, 1.32)

1.10 (0.80, 1.51)

1.14 (0.83, 1.57)

 24th -27th

38,052 (94.3)

2306 (5.7)

2112 (5.2)

194 (0.5)

8291 (94.8)

459 (5.2)

420 (4.8)

39 (0.4)

0.91 (0.82, 1.01)

0.93 (0.84, 1.03)

0.91 (0.82, 1.02)

0.93 (0.83, 1.03)

0.92 (0.65, 1.30)

0.99 (0.70, 1.40)

 28th -31st

36,145 (94.8)

2001 (5.2)

1915 (5.0)

86 (0.2)

7663 (94.6)

438 (5.4)

424 (5.2)

14 (0.2)

1.03 (0.93, 1.15)

1.05 (0.95, 1.17)

1.04 (0.94, 1.16)

1.06 (0.95, 1.19)

0.77 (0.44, 1.35)

0.80 (0.45, 1.42)

 32nd -36th

45,650 (96.3)

1732 (3.7)

1732 (3.7)

NA

9853 (96.5)

360 (3.5)

360 (3.5)

NA

0.96 (0.86, 1.08)

0.97 (0.86, 1.09)

0.96 (0.86, 1.08)

0.97 (0.86, 1.09)

NA

NA

 

Exposure dose in unexposed group

(Mean ± SD)

Exposure dose in exposed group

(Mean ± SD)

OR for PTB (95%CI)

Term + PTB

Term

PTB

MPTB + VPTB

MPTB

VPTB

MPTB + VPTB

MPTB

VPTB

Crude OR

Adjusted OR*

Crude OR

Adjusted OR*

Crude OR

Adjusted OR*

Cumulative exposure dose in the first 22 weeks during Level I to Level 3 lockdown b

 Per 100 unit increase

0 ± 0

195.14 ± 82.19

194.15 ± 82.57

194.23 ± 82.60

193.35 ± 82.38

1.06 (1.04, 1.08)

1.07 (1.05, 1.09)

1.05 (1.04 1.07)

1.07 (1.05, 1.08)

1.10 (1.05, 1.16)

1.12 (1.06, 1.18)

Categories of cumulative exposure dose

 Unexposed group

0 ± 0

–

Reference

Reference

Reference

Reference

Reference

Reference

 Q1 (< 132)

–

73.52 ± 38.09

71.59 ± 38.28

71.49 ± 38.32

72.57 ± 38.07

1.14 (1.07, 1.22)

1.16 (1.08, 1.23)

1.13 (1.05, 1.21)

1.14 (1.07, 1.22)

1.27 (1.03, 1.67)

1.31 (1.06, 1.62)

 Q2 (132–225)

–

178.64 ± 27.17

179.01 ± 27.26

179.14 ± 27.26

177.76 ± 27.29

1.21 (1.13, 1.29)

1.22 (1.14, 1.30)

1.19 (1.11, 1.27)

1.20 (1.12, 1.28)

1.39 (1.14, 1.70)

1.43 (1.17, 1.74)

 Q3 (226–263)

–

247.16 ± 10.59

247.52 ± 10.28

247.50 ± 10.26

247.91 ± 10.58

1.11 (1.04 1.19)

1.14 (1.07, 1.22)

1.10 (1.03, 1.18)

1.13 (1.05, 1.21)

1.25 (1.01, 1.54)

1.27 (1.03, 1.58)

 Q4 (≥264)

–

278.81 ± 8.57

278.69 ± 8.77

278.55 ± 8.76

280.23 ± 8.79

1.14 (1.06, 1.21)

1.19 (1.11, 1.27)

1.13 (1.05, 1.21)

1.18 (1.10, 1.26)

1.21 (0.97, 1.49)

1.25 (1.01, 1.55)

 P for trend test

      

<  0.001

 

<  0.001

 

<  0.001

  1. In calculating the cumulative exposure dose to lockdown, we assigned a weighting of 3 to days with Level I response, 2 to days with Level II response, 1 to days with Level III response, and 0 to other days
  2. PTB preterm birth, MPTB moderate preterm birth, VPTB very preterm birth
  3. N/A: There is no VPTB case in the subgroup
  4. *: Adjusted for maternal age, marital status, parity, residential city, delivery type and infant sex
  5. a Pregnant women who have experienced the COVID-19 lockdown (from 1/23/2020 to 2/24/2020) during any period of their pregnancy were defined as the exposed group. We further divided the exposed group into subgroups. According to their gestational weeks (GW) on 1/23/2020, the beginning of lockdown
  6. b: The exposed group refers to the pregnant women who have experienced the COVID-19 lockdown in their first 22 GWs. The rest of included participants were defined as the unexposed group. The individual cumulative exposure dose was calculated by combining the weightings with the overlap between their pregnancy period ≤22 GWs and the three levels of responses. Q1-Q4 were defined as the cumulative exposure dose of the exposed group classified by quartiles, and the unexposed group were used as reference
  7. -: Not applicable
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