Outcomes of assisted reproductive technology cycles following bushfire exposure: a retrospective cohort study

Does an association exist between assisted reproductive technology (ART) cycle outcomes and residential proximity to bushfires in Victoria, Australia?

Retrospective cohort study of participants undergoing oocyte retrieval at Victoria Monash IVF clinics up to 6 months before or after bushfire events (n = 2001 cycles, July 2019 to June 2020). Data were stratified by cycle date (pre- or post-fires) and by residential postcode (proximal or non-proximal to fires). The proximal regions had active fire within that post code. Analysis of variance (or Kruskal-Wallis test) and Fisher's exact test were used for continuous and categorical data, respectively. Generalized estimating equations and binary logistic regressions were also used, with adjustments for cofactors. Regression was used to access the correlation between time after fires and ART outcomes.

Numbers of oocytes retrieved and fertilized, number of embryos used, rates of fertilization, utilization, clinical pregnancy and live birth were similar between proximal and non-proximal groups after the fires. Furthermore, numbers and rates were similar between proximal groups before and after fires, and non-proximal groups before and after fires (P > 0.1). Correlation analyses revealed the strongest trend was in embryo utilization rates over time after fires in the proximal versus non-proximal group in either IVF and intracytoplasmic sperm injection (ICSI) (R² = 0.08, P = 0.057) or ICSI only cycles (R² = 0.09, P = 0.071). The correlation, however, was not statistically significant.

Residential proximity to major bushfire events was not associated with any significant alterations to ART outcomes between time- and clinic-matched cycles. As global fire events continue to rise in incidence and severity, associations between bushfire exposure and long-term reproductive outcomes are important factors to consider in future research.