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Table 2 Odds of medically-induced, spontaneous, and All PTB compared with term birth according to prepregnancy BMI a

From: Prepregnancy body mass index and risk of preterm birth: association heterogeneity by preterm subgroups

 

Medically-induced PTBb

Spontaneous PTBb

All PTBc

Crude and adjusted models

OR

95% C.I.

p-value

OR

95% C.I.

p-value

OR

95% C.I.

p-value

M1: Unadjusted

         

  < 18.5

0.75

0.42, 1.35

0.33

1.32

0.95, 1.83

0.10

1.15

0.85, 1.55

0.37

  18.5-24.9 (ref)

1.00

  

1.00

  

1.00

  

  25.0-29.9

1.28

1.01, 1.61

0.04

1.07

0.90, 1.27

0.45

1.13

0.97, 1.31

0.11

  ≥ 30.0

1.83

1.44, 2.34

<0.001

0.98

0.80, 1.20

0.85

1.23

1.04, 1.46

0.01

M2: Adjustedd

         

  <18.5

0.94

0.52, 1.71

0.84

1.40

0.99, 1.99

0.06

1.29

0.94, 1.77

0.12

  18.5-24.9 (ref)

1.00

  

1.00

  

1.00

  

  25.0-29.9

1.11

0.87, 1.43

0.39

0.99

0.82, 1.18

0.87

1.02

0.87, 1.20

0.79

  ≥ 30.0

1.59

1.23, 2.05

<0.001

0.90

0.73, 1.12

0.35

1.11

0.93, 1.33

0.25

Models to further assess mediation

         

M3: M2 + hypertensive disorders of pregnancye

         

  <18.5

1.19

0.60, 2.34

0.62

1.41

1.00, 2.00

0.05

1.38

0.99, 1.91

0.05

  18.5-24.9 (ref)

1.00

  

1.00

  

1.00

  

  25.0-29.9

0.96

0.72, 1.29

0.81

0.98

0.81, 1.17

0.80

0.97

0.83, 1.15

0.76

  ≥ 30.0

1.13

0.82, 1.54

0.46

0.91

0.73, 1.13

0.40

0.97

0.80, 1.17

0.73

M4: M2 + chorioamnionitisf

         

  <18.5

0.93

0.51, 1.69

0.81

1.48

1.04, 2.10

0.03

1.32

0.96, 1.82

0.09

  18.5-24.9 (ref)

1.00

  

1.00

  

1.00

  

  25.0-29.9

1.12

0.87, 1.43

0.39

0.99

0.83, 1.20

0.95

1.03

0.88, 1.21

0.73

  ≥ 30.0

1.58

1.22, 2.05

0.001

0.91

0.73, 1.12

0.37

1.12

0.93, 1.34

0.23

M5: M2 + gestational diabetesf

         

  <18.5

0.96

0.53, 1.75

0.90

1.42

1.00, 2.01

0.05

1.31

0.95, 1.80

0.10

  18.5-24.9 (ref)

1.00

  

1.00

  

1.00

  

  25.0-29.9

1.06

0.82, 1.36

0.66

0.96

0.79, 1.15

0.63

0.98

0.84, 1.15

0.83

  ≥ 30.0

1.40

1.08, 1.83

0.01

0.86

0.69, 1.07

0.16

1.03

0.85, 1.23

0.78

Grand model

         

M6: M2 + hypertensive disorders of pregnancye + chorioamnionitisf + gestational diabetesg

         

  <18.5

1.21

0.61, 2.39

0.58

1.51

1.06, 2.15

0.02

1.45

1.04, 2.02

0.03

  18.5-24.9 (ref)

1.00

  

1.00

  

1.00

  

  25.0-29.9

0.94

0.70, 1.27

0.69

0.95

0.79, 1.15

0.60

0.95

0.80, 1.12

0.54

  ≥ 30.0

1.08

0.78, 1.49

0.65

0.86

0.69, 1.07

0.17

0.92

0.75, 1.11

0.38

  1. BMI = Body Mass Index; PTB = Preterm Birth.
  2. aData from 466 mothers with medically-induced PTBs, 930 mothers with spontaneous PTBs, and 3281 mothers with term births.
  3. bMultinomial regression used to compare medically-induced and spontaneous PTB with term birth (reference group).
  4. cLogistic regression used to compare all PTB with term birth (reference group).
  5. dAdjusted model includes maternal age, race/ethnicity, marital status, income, education, child sex, maternal gestational weight gain, smoking, alcohol or illicit drug use, stress, parity, cervical incompetence, and placenta previa.
  6. eHypertensive disorders of pregnancy are categorized as chronic hypertension, mild preeclampsia, severe hypertensive disorders (severe preeclampsia, eclampsia, HELLP syndrome), and none.
  7. fChorioamnionitis is categorized as subclinical chorioamnionitis, clinical chorioamnionitis, and none.
  8. gMaternal diabetes is categorized as gestational diabetes or diabetes prior to pregnancy vs. none.