Adverse Reproductive Outcomes in the US Fire Service: Results From a Survey of Women Firefighters

Abstract

Background: Evidence from previous studies suggests that women firefighters have greater risk of adverse reproductive outcomes, including miscarriage and preterm birth. Some research also suggests that they are more likely to use fertility treatments, though infertility has not been previously described. Therefore, the purpose of this dissertation was to utilize a national study of women firefighters to 1) investigate occupational factors and risk of miscarriage, 2) evaluate occupational factors and risk of preterm birth, and 3) to describe infertility and fertility treatment utilization and evaluate associations between occupational factors and infertility and fertility treatment utilization. Methods: Data from the Health and Wellness of Women Firefighters Study (n=3,181), conducted by NDRI-USA was utilized. Data were self-reported via two online surveys administered in 2017 and 2019. The 2017 survey included questions covering firefighter occupational details and pregnancy history. The 2019 survey included questions assessing reproductive history (specifically infertility and fertility treatment utilization) that were developed by the author. Self-reported infertility was assessed and firefighters who experienced infertility reported additional details about their infertility and fertility treatment history.Data from the 2017 survey were used to study miscarriages and preterm births (PTBs) among pregnancies of US women firefighters. Prevalence of miscarriage and PTB among firefighters were compared to published rates from non-firefighters using age-at-pregnancy-standardized prevalence ratios (aSPRs). Generalized estimating equations were used to estimate relative risks (RRs) and 95% confidence intervals (CIs) between occupational factors and risk of miscarriage or risk of PTB. Models were adjusted for age at pregnancy, education, gravidity, BMI, and smoking. Variation by age at pregnancy or employment (career firefighter vs volunteer) were also evaluated. Data from the 2019 survey were examined to study infertility among firefighters. The distribution of infertility diagnoses and levels of fertility treatment utilization were described. Log binomial regression models were used to estimate RRs and 95% CIs between occupational factors and risk of infertility, and considered age at survey, BMI, and smoking as potential confounders. Additionally, among firefighters who reported infertility, associations between occupational factors and access to fertility care, any fertility treatment, and in vitro fertilization (IVF)/intrauterine insemination (IUI) were examined using log binomial models and age as a potential confounder. Results: An estimated 22% of all pregnancies that occurred while working in the fire service resulted in a miscarriage. Compared to a study of US nurses, firefighters had 2.33 times greater prevalence of miscarriage (95% CI 1.96-2.75). We observed that volunteers had a greater risk for miscarriage compared to career firefighters, which varied by wildland firefighter status (structural firefighters: RR 1.42, 95% CI 1.11-1.80; wildland/wildland-urban interface (WUI) firefighters: RR 2.53, 95% CI 1.35-4.78). Women who had livebirths while working in the fire service reported that 12% were born prematurely. The prevalence of PTBs among firefighters was 1.41 times greater compared to the general population (95% CI 1.18-1.68). Among wildland/WUI firefighters, volunteer firefighters had 2.82 times the risk of PTB (95% CI 1.19-6.67) compared to career firefighters. Our results also suggested that the timing of when work restriction was started during pregnancy may have influenced risk of PTB. Among women who responded to questions regarding their reproductive health, 16% reported a history of infertility. Most firefighters who experienced infertility had visited a clinician to discuss their infertility (81%) and utilized some form of fertility treatment (55%). The most common medically confirmed diagnoses were polycystic ovary syndrome (18%) and endometriosis (15%). Among those who had used any fertility treatment, 42% reported utilization of in vitro fertilization and 46% reported utilization of intrauterine insemination. We observed no difference in risk of infertility by occupational factors, though results suggested that total years of service may affect risk of infertility. We also observed no differences in access to fertility care or treatment utilization by occupational factors among women who had experienced infertility, though our results suggested that employment and wildland firefighter status my influence utilization of IVF or IUI. Conclusions: Results of this research are consistent with previous studies that have suggested that women firefighters may have greater risk of some adverse reproductive outcomes compared to non-firefighters. Our findings also suggest that there may be variation in risk of these outcomes by fire service role (career firefighter vs volunteer, wildland or WUI vs structural). Further research is needed to clarify these associations to help shape future policy development in the fire service and personal decision-making.