Table 1 Descriptive results for the complete cohort.

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

 

Non-Exposed

(N=15117)

Exposed

(N=10229)

Combined

(N=25346)

P value

Categories or Statistic

N (%)

N (%)

N (%)

Exposure Variables

Days of PM2.5 Exposure (>25µg/m3)

Mean (SD)

0 (0)

15.30 (14.97)

6.18 (12.12)

<0.001

Median (IQR)

0 (0)

9 (30)

0 (2)

Range

0

1-64

0-64

PM2.5 Tower

Armidale

32 (0.21)

712 (6.96)

744 (2.94)

<0.001

Beresfield

11,527 (76.25)

6526 (63.80)

18053 (71.23)

Gunnedah

107 (0.71)

317 (3.63)

478 (1.89)

Muswellbrook

173 (1.14)

796 (7.78)

969 (3.82)

Narrabri

132 (0.87)

229 (2.24)

361 (1.42)

Singleton

694 (4.59)

1023 (10.0)

1717 (6.77)

Tamworth

2452 (16.22)

572 (5.59)

3024 (11.93)

Maternal Variables

Anaemia

No

7496 (49.59)

4489 (43.89)

11985 (47.29)

<0.001

Yes

2987 (19.76)

1885 (19.41)

4972 (19.62)

Unknown

4634 (30.65)

3755 (36.71)

8389 (33.10)

Birth Type

Vaginal

9270 (61.32)

6097 (59.61)

15367 (60.63)

0.002

Instrumental

1357 (8.98)

879 (8.59)

2236 (8.82)

Caesarean

4490 (29.70)

3253 (31.80)

7743 (30.55)

BMI

Mean (SD)

26.74 (6.74)

26.88 (6.58)

26.79 (6.68)

0.093

Median (IQR)

25.15 (8.36)

25.44 (10.39)

25.26 (8.24)

Range

12.5-69.56

9.21-72.84

9.21-72.84

Diabetes

No

13286 (87.89)

8981 (87.80)

22267 (87.85)

0.932

Yes

1772 (11.72)

1205 (11.78)

2977 (11.75)

Unknown

59 (0.39)

43 (0.42)

102 (0.40)

Ethnicity

Indigenous

1695 (11.21)

1164 (11.38)

2859 (11.28)

<0.001

Non-Indigenous

13261 (87.72)

9052 (88.49)

22313 (88.03)

Unknown

161 (1.07)

13 (0.13)

174 (0.69)

Hypertension

No

14230 (94.13)

9593 (93.78)

23823 (93.99)

0.514

Yes

874 (5.78)

627 (6.13)

1501 (5.92)

Unknown

13 (0.09)

9 (0.09)

22 (0.09)

Maternal Age (years)

Mean (SD)

29.33 (5.49)

29.438 (5.42)

29.435 (5.46)

0.451

Median (IQR)

29 (8)

29 (7)

29 (8)

Range

14-51

15-49

14-51

Previous Pregnancies

No

5523 (36.54)

3602 (35.21)

9125 (36.00)

0.032

Yes

9594 (63.46)

6627 (64.79)

16221 (64.00)

Smoking

No

12518 (82.81)

8502 (83.12)

21020 (82.93)

0.521

Yes

2599 (17.19)

1727 (16.88)

4326 (17.07)

Infant Variables

Birthweight (g)

Mean (SD)

3405.08 (561.83)

3405.22 (555.64)

3405.13 (559.33)

0.985

Median (IQR)

3440 (330)

3440 (690)

3440 (670)

Range

439-5650

570-5410

439-560

Birthweight Percentile

Mean (SD)

0.56 (0.29)

0.55 (0.29)

0.55 (0.29)

0.104

Median (IQR)

0.58 (0.5)

0.57 (0.51)

0.58 (0.50)

Range

0.03-0.98

0.03-0.98

0.03-0.98

Foetal Growth Restriction

No

14251 (94.27)

9658 (94.42)

23909 (94.33)

0.884

Yes

496 (3.28)

333 (3.26)

829 (3.27)

Clinical Suspicion

356 (2.35)

227 (2.22)

583 (2.30)

Unknown

14 (0.09)

11 (0.11)

25 (0.10)

Gender

Male

7823 (51.75)

5245 (51.28)

13068 (51.56)

0.459

Female

7294 (48.25)

4984 (48.72)

12278 (48.44)

Gestation (days)

Mean (SD)

274.02 (12.82)

274.36 (12.49)

274.16 (12.69)

0.039

Median (IQR)

275 (13)

276 (13)

275 (13)

Range

168-304

168-314

168-314

  1. Complete cohort results demonstrating those exposed to at least 1 day of PM2.5 over the designated threshold of 25µg/m3 or no days over the threshold and total cohort.
  2. 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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