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Table 3 Associations between occupational factors and risk of miscarriage among 1074 firefighters and 1864 pregnanciesa,b

From: Occupational factors and miscarriages in the US fire service: a cross-sectional analysis of women firefighters

 

Miscarriages

N (%)

RR (95% CI)

Model 1c

RR (95% CI)

Model 2d

Firefighter subgroups

 Employment, stratified by wildland firefighter status

  Structural

No

Yes

  

   Career

891 (76%)

281 (24%)

1.00 (Ref.)

1.00 (Ref.)

   Volunteer

140 (69%)

64 (31%)

1.41 (1.11–1.79)

1.42 (1.11–1.80)

  Wildland/WUI

No

Yes

  

   Career

388 (90%)

41 (10%)

1.00 (Ref.)

1.00 (Ref.)

   Volunteer

38 (68%)

18 (32%)

3.09 (1.76–5.42)

2.53 (1.35–4.78)

  Interaction p-value e

  

< 0.01

< 0.01

Work practices

 Shift schedule of career firefighters, stratified by age at pregnancy

   < 35 years old

No

Yes

  

   Less than 24 h on shift

232 (77%)

69 (23%)

1.00 (Ref.)

1.00 (Ref.)

   24 or more hr. on shift

772 (84%)

144 (16%)

0.67 (0.50–0.90)

0.74 (0.55–0.99)

  35+ years old

No

Yes

  

   Less than 24 h on shift

64 (78%)

18 (22%)

1.00 (Ref.)

1.00 (Ref.)

   24 or more hr. on shift

211 (70%)

89 (30%)

1.29 (0.84–2.00)

1.28 (0.82–1.99)

  Interaction p-value f

  

0.01

0.02

  Worked fire/rescue calls at pregnancy start

No

Yes

  

   No

138 (70%)

58 (30%)

1.00 (Ref.)

1.00 (Ref.)

   Yes

1250 (79%)

340 (21%)

0.81 (0.60–1.09)

0.82 (0.61–1.11)

  1. RR Relative risk, CI confidence interval, BMI Body mass index (kg/m2), WUI wildland urban interface
  2. a Generalized estimating equations models with Poisson distribution and sandwich variance estimators were used to estimate risk ratios and 95% CIs
  3. b 86 pregnancies had missing information for wildland status (3), shift schedule (5) and fire/rescue calls (78) and were not included in those models
  4. c Model 1 is adjusted for age at pregnancy, modeled as age at pregnancy and (age at pregnancy)2
  5. d Model 2 is additionally adjusted for highest education completed (some college/at least college degree), gravidity (yes/no), BMI (< 30 kg/m2 / ≥30 kg/m2), and smoking status (current or former/never). Highest education completed, BMI, and smoking status were measured in 2017 at time of survey. Gravidity was assessed for each pregnancy
  6. e p-value for interaction between employment and wildland firefighter status
  7. f p-value for interaction between shift schedule and age at pregnancy, among career firefighters
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Environmental Health

ISSN: 1476-069X