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Table 1 Maternal and infant characteristics by maternal smoking behavior during pregnancy; non-smokers, early stoppers and late- or non-stoppers

From: Women who smoke during pregnancy are more likely to be referred to an obstetrician during pregnancy and birth: results from a cohort study

 

Total population

N = 41 088

Non-smokers

n = 34 102 (83.0%)

Early stoppers

n = 3217 (7.8%)

Late- or non- stoppers

n = 3769 (9.2%)

Statistical differences between subgroups that differed in smoking status

 

N (%)a

n (%)a

n (%) a

n (%)a

p-value

Maternal characteristics

Maternal age (in years)

    

 ≤ 0.001

  < 20

249 (0.6)

118 (0.3)

54 (1.7)

77 (2.0)

 

 20–24

3209 (7.8)

1997 (5.9)

438 (13.6)

774 (20.5)

 

 25–29

12 499 (30.4)

9939 (29.1)

1200 (37.3)

1360 (36.1)

 

 30–34

16 660 (40.5)

14 577 (42.7)

1055 (32.8)

1028 (27.3)

 

 35–39

7331 (17.8)

6482 (19.0)

410 (12.7)

439 (11.6)

 

  > 39

1140 (2.8)

989 (2.9)

60 (1.9)

91 (2.4)

 

BMIa

    

 ≤ 0.001

 Underweight

1266 (3.1)

944 (2.8)

97 (3.0)

225 (6.0)

 

 Normal weight

24 251 (59.0)

20 521 (60.2)

1831 (56.9)

1899 (50.4)

 

 Pre-obesity

9542 (23.2)

7867 (23.1)

753 (23.4)

922 (24.5)

 

 Obesity class I

3496 (8.5)

2741 (8.0)

333 (10.4)

422 (11.2)

 

 Obesity class II

1170 (2.8)

915 (2.7)

103 (3.2)

152 (4.0)

 

 Obesity class II

270 (0.7)

210 (0.6)

27 (0.8)

33 (0.9)

 

 Missing

1093 (2.7)

904 (2.7)

73 (2.3)

116 (3.1)

 

Ethnic backgroundb

    

 ≤ 0.001

 Dutch

31 271 (76.1)

25 965 (76.1)

2462 (76.5)

2844 (75.5)

 

 Western (non-Dutch)

2668 (6.5)

2107 (6.2)

275 (8.5)

286 (7.6)

 

 Non-Western

3892 (9.5)

3407 (10.0)

195 (6.1)

290 (7.7)

 

 Other

243 (0.6)

183 (0.5)

33 (1.0)

27 (0.7)

 

 Missing

3014 (7.3)

2440 (7.2)

252 (7.8)

322 (8.5)

 

Socio economic statusc

 Low

12 942 (31.5)

9874 (29.0)

1170 (36.4)

1898 (50.4)

 ≤ 0.001

 Middle

20 841 (50.7)

17 643 (51.7)

1626 (50.5)

1572 (41.7)

 

 High

6992 (17.0)

6325 (18.5)

394 (12.2)

273 (7.2)

 

 Missing

313 (0.8)

260 (0.8)

27 (0.8)

26 (0.7)

 

Marital status

    

 ≤ 0.001

 Single

926 (2.3)

515 (1.5)

117 (3.6)

294 (7.8)

 

 In a relationship

39 040 (95.0)

32 832 (96.3)

2964 (92.1)

3244 (86.1)

 

 Missing

1122 (2.7)

755 (2.2)

136 (4.2)

231 (6.1)

 

Parity

    

 ≤ 0.001

 Nulliparous

19 300 (47.0)

15 616 (45.8)

1989 (61.8)

1695 (45.0)

 

 Multiparous

21 788 (53.0)

18 486 (54.2)

1228 (38.2)

2074 (55.0)

 

Gestational age at birth

    

 ≤ 0.001

 Extremely preterm (< 28 weeks)

337 (0.8)

272 (0.8)

25 (0.8)

40 (1.1)

 

 Very preterm (28–32 weeks)

196 (0.5)

159 (0.5)

14 (0.4)

23 (0.6)

 

 Moderate to late preterm (32–37 weeks)

1535 (3.7)

1184 (3.5)

138 (4.3)

213 (5.7)

 

 Term (37–42)

36 109 (87.9)

30 136 (88.4)

2783 (86.5)

3190 (84.6)

 

 Postterm (≥ 42 weeks)

547 (1.3)

478 (1.4)

41 (1.3)

28 (0.7)

 

 Missing

2364 (5.8)

1873 (5.5)

216 (6.7)

275 (7.3)

 

Lifestyle

Alcohol consumptiond

    

 ≤ 0.001

 No

24 367 (59.3)

20 310 (59.6)

1875 (58.3)

2182 (57.9)

 

 Yes

241 (0.6)

183 (0.5)

28 (0.9)

30 (0.8)

 

 Stopped after a positive  pregnancy test

611 (1.5)

448 (1.3)

106 (3.3)

57 (1.5)

 

Missing

15 869 (38.6)

13 161 (38.6)

1208 (37.6)

1500 (39.8)

 

Drug consumptione

    

 ≤ 0.001

 No

22 700 (55.2)

18 949 (55.6)

1767 (54.9)

1984 (52.6)

 

 Yes

182 (0.4)

56 (0.2)

43 (1.3)

83 (2.2)

 

 Stopped recently

150 (0.4)

25 (0.1)

56 (1.7)

69 (1.8)

 

 Missing

18 056 (43.9)

15 072 (44.2)

1351 (42.0)

1633 (43.3)

 

Pregnancy complicationsf

     

 Gestational Diabetes Mellitus

1385 (3.4)

1142 (3.3)

106 (3.3)

137 (3.6)

0.63

 Hypertensive disorder

2311 (5.6)

1925 (5.6)

220 (6.8)

166 (4.4)

 ≤ 0.001

 Placenta previa

212 (0.5)

177 (0.5)

17 (0.5)

18 (0.5)

0.94

 Fetal growth restriction

1489 (3.6)

1055 (3.1)

131 (4.1)

303 (8.0)

 ≤ 0.001

Mode of birth characteristics

    

 ≤ 0.001

 Spontaneous vaginal birth

30 327 (73.8)

25 358 (74.4)

2223 (69.1)

2746 (72.9)

 

 Instrumental birth

3212 (7.8)

2639 (7.7)

301 (9.4)

272 (7.2)

 

 Cesarean delivery

4060 (9.9)

3317 (9.7)

379 (11.8)

364 (9.7)

 

 Other

695 (1.7)

578 (1.7)

61 (1.9)

56 (1.5)

 

 Missing

2794 (6.8)

2210 (6.5)

253 (7.9)

331 (8.8)

 

Maternal Outcomes

    

 ≤ 0.001

 Postpartum hemorrhage > 1000 ml

1227 (3.0)

1032 (3.0)

104 (3.2)

91 (2.4)

 

Infant characteristics

Sex

    

0.005

 Female

18 819 (45.8)

15 688 (46.0)

1383 (43.0)

1748 (46.4)

 

 Male

19 837 (48.3)

16 490 (48.4)

1612 (50.1)

1735 (46.0)

 

 Missing

2432 (5.9)

1924 (5.6)

222 (6.9)

286 (7.6)

 

Birthweight (grams)

    

 ≤ 0.001

  ≤ 1500

415 (1.0)

323 (0.9)

33 (1.0)

59 (1.6)

 

 1501–2500

1271 (3.1)

854 (2.5)

120 (3.7)

297 (7.9)

 

 2501–3500

18 052 (43.9)

14 519 (42.6)

1438 (44.7)

2095 (55.6)

 

 3501–4500

18 055 (43.9)

15 709 (46.1)

1342 (41.7)

1004 (26.6)

 

  ≥ 4501

750 (1.8)

671 (2.0)

55 (1.7)

24 (0.6)

 

 Missing

2545 (6.2)

2026 (5.9)

229 (7.1)

290 (7.7)

 

Mortality

    

0.125

 Fetal death

273 (0.7)

218 (0.6)

18 (0.6)

37 (1.0)

 

 Neonatal death

43 (0.1)

37 (0.1)

2 (0.1)

4 (0.1)

 
  1. Percentages may not add up to 100% due to rounding
  2. aBMI classified as: Underweight (< 18.5), Normal Weight (18.5–24.9), Pre-obesity (25.0–29.9), Obesity class I (30.0–34.9), Obesity class II (35.0–39.9), Obesity class III (> 40)
  3. bEthnic background classified as: Dutch, Western non-Dutch (European), Non-Western (African, Asian, Turkish, Moroccan) and other migration backgrounds
  4. cSocioeconomic status classified as: Low (below the 25th percentile), Middle (between the 25th and 50th percentile), High (above the 75th percentile)
  5. dAlcohol consumption: No (no alcohol use), Yes (ranging from occassional use to daily use), Stopped after a positive pregnancy test
  6. e Drugs consumption: No (no drug use), Yes (ranging from occasional use to daily use), Stopped recently
  7. fMultiple pregnancy complications are possible, therefore they do not add up to 100%
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