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Table 1 Characteristics of Mother-Infant pairs according to delivery type

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

 

Medically-induced PTBsa

Spontaneous PTBsa

Term birthsb

p-valuec

 

(N = 466)

(N = 930)

(N = 3281)

 
 

Mean (SD)

 

Maternal age (years)

29.5 (6.8)

28.0 (6.6)

27.8 (6.4)

<0.001

Gestational age at birth (weeks)

33.7 (3.0)

33.7 (3.4)

39.5 (1.3)

<0.001

Prepregnancy BMI (kg/m2)

27.1 (6.6)

25.5 (6.0)

25.8 (6.1)

<0.001

Birth weight (grams)

1989 (734)

2237 (716)

3239 (563)

<0.001

 

N (%)

 

Prepregnancy BMI (kg/m2)

   

<0.001

  <18.5

13 (2.8)

54 (5.8)

149 (4.5)

  18.5-24.9

188 (40.3)

444 (47.7)

1613 (49.2)

  25.0-29.9

136 (29.2)

269 (28.9)

915 (27.9)

  ≥ 30.0

129 (27.7)

163 (17.5)

604 (18.4)

Hypertensive disorders of pregnancy

   

<0.001

  None

179 (38.7)

850 (92.1)

3004 (92.2)

  Chronic hypertension

19 (4.1)

27 (2.9)

71 (2.2)

  Mild preeclampsia

60 (13.0)

24 (2.6)

123 (3.8)

  Severe hypertensive disorders (severe pre-eclampsia, eclampsia, HELLP syndrome)

205 (44.3)

22 (2.4)

61 (1.9)

Chorioamnionitis

   

<0.001

  None

125 (26.8)

252 (27.1)

1265 (38.6)

  Subclinical chorioamnionitis

117 (25.1)

157 (16.9)

578 (17.6)

  Clinical chorioamnionitis

35 (7.5)

239 (25.7)

302 (9.2)

Unknown

189 (40.6)

282 (30.3)

1136 (34.6)

Glucose tolerance

   

<0.001

  No

401 (86.4)

855 (92.3)

3090 (94.5)

  Gestational diabetes

39 (8.4)

46 (5.0)

145 (4.4)

  Diabetes mellitus before index pregnancy

24 (5.2)

25 (2.7)

35 (1.1)

Gestational weight gain per 2009 IOM

   

<0.001

  Inadequate

50 (10.7)

118 (12.7)

479 (14.6)

  Adequate

38 (8.2)

115 (12.4)

635 (19.4)

  Excessive

148 (31.8)

306 (32.9)

853 (26.0)

  Unknown

230 (49.4)

391 (42.0)

1314 (40.0)

Married

159 (34.2)

250 (26.9)

1183 (36.2)

<0.001

Household income

   

0.13

  < $30,000/yr

213 (45.7)

475 (51.1)

1580 (48.2)

  ≥ $30,000/yr

69 (14.8)

100 (10.8)

387 (11.8)

  Unknown

184 (39.5)

355 (38.2)

1314 (40.0)

Education

   

0.02

  < High school

138 (29.6)

310 (33.3)

1100 (33.5)

  High school

176 (37.8)

336 (36.1)

1055 (32.2)

  > High school

152 (32.6)

284 (30.5)

1126 (34.3)

Maternal race/ethnicity

   

0.003

  White

52 (11.2)

130 (14.0)

342 (10.4)

  Black

260 (55.8)

482 (51.8)

1646 (50.2)

  Hispanic

106 (22.7)

213 (22.9)

892 (27.2)

  Other

48 (10.3)

105 (11.3)

401 (12.2)

Maternal smoking 3 months before or during index pregnancy

98 (21.0)

275 (29.6)

591(18.0)

<0.001

Maternal stress during pregnancy

   

<0.001

  No stress

144 (31.1)

304 (33.1)

1269 (38.9)

  Average stress

194 (41.9)

396 (43.1)

1385 (42.4)

  Very stressful

125 (27.0)

218 (23.7)

612 (18.7)

Any illicit drug use during pregnancy

76 (16.5)

218 (23.5)

432 (13.2)

<0.001

Alcohol use during pregnancy

30 (6.5)

65 (7.0)

211 (6.4)

0.84

Parity

   

0.02

  Nulliparous

207 (44.4)

385 (41.4)

1381 (42.1)

  Primiparous

119 (25.5)

239 (25.7)

977 (29.8)

  Multiparous

140 (30.0)

306 (32.9)

923 (28.1)

Cervical incompetence

16 (3.4)

64 (6.9)

37 (1.1)

<0.001

Placenta previa

22 (4.7)

29 (3.1)

32 (1.0)

<0.001

Preterm premature rupture of membranes

0 (0.0)

439 (47.2)

0 (0.0)

N/A

Mode of delivery

   

<0.001

  Vaginal

136 (29.2)

695 (74.8)

2302 (70.2)

  Cesarean section

330 (70.8)

234 (25.2)

977 (29.8)

Delivery type

   

N/A

  Medically-induced

466 (100.0)

0 (0.0)

971 (29.6)

  Spontaneous

0 (0.0)

930 (100.0)

2310 (70.4)

PTB according to gestational age

  

N/A

N/A

  Early PTB (<34 weeks)

189 (40.6)

320 (34.4)

  Late PTB (34–36 weeks)

277 (59.4)

610 (65.6)

Infant sex- female

247 (53.0)

447 (48.1)

1656 (50.5)

0.20

  1. PTB = Preterm Birth; BMI = Body Mass Index; IOM = Institute of Medicine; HELLP = hemolysis, elevated liver enzymes, low platelets.
  2. aPTBs include births at 23–36 weeks gestation.
  3. bTerm Births include births at 37–44 weeks gestation.
  4. cP-values calculated from chi-square tests for categorical variables and ANOVA for continuous variables.