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Table 3 Odds of early and late medically-induced and spontaneous PTB compared with term birth according to prepregnancy BMI a,b

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

  Early medically-induced PTB Late medically-induced PTB Early spontaneous PTB Late spontaneous PTB
Crude and adjusted models OR 95% C.I. p-value OR 95% C.I. p-value OR 95% C.I. p-value OR 95% C.I. p-value
M1: Unadjusted             
  < 18.5 0.33 0.08, 1.37 0.13 0.97 0.51, 1.83 0.92 1.30 0.76, 2.20 0.34 1.33 0.91, 1.94 0.15
  18.5-24.9 (ref) 1.00    1.00    1.00    1.00   
  25.0-29.9 1.95 1.38, 2.76 <0.001 0.92 0.67, 1.25 0.59 1.12 0.85, 1.47 0.43 1.04 0.85, 1.28 0.67
  ≥ 30.0 2.05 1.40, 3.01 <0.001 1.72 1.27, 2.31 <0.001 1.34 0.99, 1.80 0.06 0.81 0.63, 1.05 0.11
M2: Adjustedc             
  <18.5 0.43 0.10, 1.80 0.25 1.18 0.61, 2.27 0.62 1.30 0.73, 2.30 0.37 1.46 0.99, 2.16 0.06
  18.5-24.9 (ref) 1.00    1.00    1.00    1.00   
  25.0-29.9 1.68 1.16, 2.41 0.01 0.81 0.59, 1.13 0.21 1.02 0.76, 1.37 0.90 0.98 0.79, 1.21 0.84
  ≥ 30.0 1.78 1.19, 2.66 0.01 1.49 1.09, 2.04 0.01 1.25 0.90, 1.72 0.18 0.76 0.58, 0.98 0.04
Models to assess mediation             
M3: M2 + hypertensive disorders of pregnancyd             
  <18.5 0.63 0.14, 2.84 0.55 1.35 0.66, 2.76 0.41 1.31 0.74, 2.33 0.35 1.47 0.99, 2.17 0.06
  18.5-24.9 (ref) 1.00    1.00    1.00    1.00   
  25.0-29.9 1.52 1.00, 2.33 0.05 0.73 0.52, 1.04 0.08 1.02 0.75, 1.37 0.91 0.97 0.78, 1.19 0.74
  ≥ 30.0 1.17 0.73, 1.87 0.53 1.12 0.79, 1.59 0.53 1.27 0.92, 1.75 0.15 0.76 0.58, 0.99 0.04
M4: M2 + chorioamnionitise             
  <18.5 0.42 0.10, 1.77 0.24 1.17 0.61, 2.26 0.63 1.48 0.81, 2.70 0.20 1.48 1.00, 2.19 0.05
  18.5-24.9 (ref) 1.00    1.00    1.00    1.00   
  25.0-29.9 1.70 1.18, 2.45 0.01 0.81 0.59, 1.12 0.21 1.04 0.76, 1.42 0.82 0.98 0.79, 1.21 0.86
  ≥ 30.0 1.77 1.18, 2.64 0.01 1.49 1.09, 2.04 0.01 1.30 0.93, 1.83 0.13 0.76 0.58, 0.98 0.04
M5: M2 + gestational diabetesf             
  <18.5 0.44 0.10, 1.82 0.26 1.22 0.63, 2.33 0.56 1.32 0.74, 2.34 0.34 1.48 1.00, 2.19 0.05
  18.5-24.9 (ref) 1.00    1.00    1.00    1.00   
  25.0-29.9 1.64 1.14, 2.36 0.01 0.75 0.54, 1.04 0.09 0.99 0.73, 1.33 0.93 0.95 0.77, 1.18 0.64
  ≥ 30.0 1.68 1.12, 2.52 0.01 1.25 0.90, 1.74 0.18 1.16 0.84, 1.61 0.37 0.73 0.56, 0.95 0.02
Grand model             
M6: M2 + hypertensive disorders of pregnancyd + chorioamnionitise + gestational diabetesf             
  <18.5 0.63 0.14, 2.86 0.55 1.39 0.68, 2.82 0.36 1.52 0.83, 2.78 0.17 1.50 1.01, 2.22 0.04
  18.5-24.9 (ref) 1.00    1.00    1.00    1.00   
  25.0-29.9 1.58 1.03, 2.42 0.04 0.69 0.49, 0.99 0.04 0.99 0.72, 1.37 0.98 0.94 0.76, 1.16 0.56
  ≥ 30.0 1.22 0.76, 1.98 0.41 1.01 0.70, 1.45 0.96 1.19 0.84, 1.69 0.33 0.73 0.56, 0.95 0.02
  1. BMI = Body Mass Index; PTB = Preterm Birth.
  2. aData from 189 mothers with early medically-induced PTBs, 277 mothers with late medically-induced PTBs, 320 mothers with early spontaneous PTBs, 610 mothers with late spontaneous PTBs, and 3281 mothers with term births.
  3. bMultinomial regression used to compare early and late medically-induced and spontaneous PTB with term birth (reference group).
  4. cAdjusted 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.
  5. dHypertensive disorders of pregnancy are categorized as chronic hypertension, mild preeclampsia, severe hypertensive disorders (severe preeclampsia, eclampsia, HELLP syndrome), and none.
  6. eChorioamnionitis is categorized as subclinical chorioamnionitis, clinical chorioamnionitis, and none.
  7. fMaternal diabetes is categorized as gestational diabetes or diabetes prior to pregnancy vs. none.