Table 2 Descriptive results for people who identified as having smoked during pregnancy at any time compared to those who did not.

From: Effects of PM2.5 exposure during high bushfire smoke days on birthweight and gestational age in Hunter New England, NSW, Australia. A study on pregnant people who smoke and don’t smoke

Variable

Category

Non-Smoking

(N = 21020)

Smoking

(N = 4326)

P value

N (%)

N (%)

Exposure Variables

Days of PM2.5 Exposure (> 25 µg/m 3 )

Mean (SD)

6.19 (12.13)

6.10 (12.07)

0.642

Median (IQR)

0 (2)

0 (2)

Range

0–64

0–64

PM2.5 Tower Location

Armidale

620 (2.95)

124 (2.87)

< 0.001

Beresfield

15,202 (72.32)

2851 (65.90)

Gunnedah

386 (1.84)

92 (2.31)

Muswellbrook

732 (3.48)

237 (5.48)

Narrabri

282 (1.34)

79 (1.83)

Singleton

1465 (6.97)

252 (5.83)

Tamworth

2333 (11.10)

691 (15.97)

Maternal Variables

Anaemia

No

9928 (47.23)

2057 (47.55)

0.782

Yes

4140 (19.70)

832 (19.23)

Unknown

6952 (33.07)

1437 (33.22)

Birth Type

Vaginal

12,577 (59.83)

2790 (64.49)

< 0.001

Instrumental

1945 (9.25)

291 (6.73)

Caesarean

6498 (30.91)

1245 (28.78)

BMI

Mean (SD)

26.84 (6.63)

26.56 (6.88)

0.011

Median (IQR)

25.26 (8.15)

25.28 (8.98)

Range

9.21–72.84

11.72–64.44

Diabetes

No

18,448 (87.95)

3779 (87.36)

< 0.001

Yes

2477 (11.78)

500 (11.56)

Unknown

55 (0.26)

47 (1.09)

Ethnicity

Indigenous

1793 (8.53)

1066 (24.64)

< 0.001

Non-Indigenous

19,075 (90.75)

3238 (74.85)

Unknown

152 (0.72)

22 (0.51)

Hypertension

No

19,702 (93.73)

4121 (95.26)

< 0.001

Yes

1308 (6.22)

193 (4.46)

Unknown

10 (0.05)

12 (0.28)

Maternal Age (Years)

Mean (SD)

29.71 (5.30)

27.61 (5.89)

< 0.001

Median (IQR)

30 (7)

27 (9)

Range

14–51

15–50

Previous Pregnancies

No

7903 (37.60)

1222 (28.25)

< 0.001

Yes

13,117 (62.40)

3104 (71.75)

Infant Variables

Birthweight (g)

Mean (SD)

3450.48 (541.31)

3184.82 (592.25)

< 0.001

Median (IQR)

3480 (650)

3210 (740)

Range

439–5650

570–5420

Birthweight Percentile

Mean (SD)

0.57 (0.28)

0.45 (0.30)

< 0.001

Median (IQR)

0.60 (0.48)

0.43 (0.53)

Range

0.03–0.98

0.03–0.98

Foetal Growth Restriction

No

20,116 (95.70)

3793 (87.68)

< 0.001

Yes

531 (2.53)

298 (6.89)

Clinical Suspicion

358 (1.70)

225(5.20)

Unknown

15 (0.07)

10 (0.23)

Gender

Male

10,867 (51.70)

2201 (50.88)

0.326

Female

10,153 (48.30)

2125 (49.12)

Gestation (days)

Mean (SD)

274.76 (12.38)

271.29 (13.74)

< 0.001

Median (IQR)

276 (13)

273 (14)

Range

168–314

169–303

  1. Key: P value results reflect chi-squared values for categorical variables and mean t-test values for continuous variables. “PM2.5 tower” denotes the suburb location of the air quality monitoring site from which the exposure variables were collected.
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