Table 2 Interrupted time series analysis of monthly preterm birth rate in singleton and multiple pregnancies in China, 2012–2020

From: Interrupted-time-series analysis of the immediate impact of COVID-19 mitigation measures on preterm birth in China

 

Singleton births

Multiple births

β (Coefficient)

P-value

95%CI

β (Coefficient)

P-value

95%CI

Preterm

 Baseline intercept

8.91

<0.001

6.02–11.81

50.56

<0.001

39.75–61.36

 Baseline slope

0.030

0.002

0.011–0.049

0.056

0.048

0.001–0.112

 Intervention-Intercept change

−0.675

0.002

−1.091~−0.260

−2.797

0.002

−4.507~−1.088

 Intervention-Slope change

0.095

<0.001

0.048–0.142

0.801

<0.001

0.384–1.218

Very preterm

 Baseline intercept

0.77

<0.001

0.43–1.12

4.35

0.011

1.00–7.71

 Baseline slope

0.003

0.052

−0.001–0.005

0.009

0.350

−0.011–0.029

 Intervention-Intercept change

-0.025

0.375

−0.082–0.031

0.186

0.715

−0.819–1.191

 Intervention-Slope change

0.005

0.215

−0.003–0.013

0.026

0.843

−0.235–0.288

Moderate preterm

 Baseline intercept

1.06

<0.001

0.653–1.468

6.15

0.026

0.75–11.55

 Baseline slope

0.003

0.067

−0.001–0.005

−0.001

0.927

−0.027–0.024

 Intervention-Intercept change

-0.073

0.005

−0.123~−0.022

−0.424

0.310

−1.248–0.400

 Intervention-Slope change

0.008

0.004

0.003–0.013

0.113

0.090

−0.018–0.244

Late preterm

 Baseline intercept

7.08

<0.001

4.52–9.64

40.06

<0.001

31.35–48.76

 Baseline slope

0.025

0.002

0.009~0.041

0.048

0.046

0.001–0.095

 Intervention-Intercept change

−0.577

0.001

−0.921~−0.234

−2.559

<0.001

−3.812~−1.307

 Intervention-Slope change

0.082

<0.001

0.050–0.114

0.662

<0.001

0.481–0.843

Spontaneous preterm

 Baseline intercept

5.41

<0.001

3.43–7.39

19.70

<0.001

13.06–26.35

 Baseline slope

0.020

0.007

0.005–0.034

0.036

0.082

−0.005–0.077

 Intervention-Intercept change

-0.458

0.005

−0.773~−0.142

−1.714

0.015

−3.093~−0.334

 Intervention-Slope change

0.032

0.143

−0.011–0.075

0.153

0.242

−0.105–0.412

Iatrogenic preterm

 Baseline intercept

3.50

<0.001

2.52–4.49

30.85

<0.001

22.07–39.63

 Baseline slope

0.011

<0.001

0.005–0.016

0.020

0.413

−0.028–0.068

 Intervention-Intercept change

−0.218

0.019

−0.399~−0.036

−1.084

0.208

−2.779~–0.612

 Intervention-Slope change

0.063

<0.001

0.036~0.090

0.648

<0.001

0.303–0.992

  1. The p values are two-sided.
  2. CI: confidence interval.
  3. Baseline: January 1, 2012 to January 31, 2020.
  4. Intervention stage: February 1, 2020 to December 31, 2020.
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