Oral or Poster Presentation
Concurrent Session 4A - Perinatal Epidemiology
Sarka Lisonkova, PhD
1. Department of Obstetrics and Gynaecology, University of British Columbia and the Children’s and Women’s Hospital and Health Centre of British Columbia, Vancouver, BC, Canada. 2. School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada.
KS Joseph, MD, PhD
Department of Obstetrics and Gynaecology, Children's & Women's Health Centre of British Columbia; University of British Columbia; Women's Health Research Institute; BC Children's Hospital Research Institute
Introduction: The pathophysiology of obesity-associated perinatal death is not completely understood. Higher rates of perinatal death in women with pre-pregnancy obesity may be partly due to lower gestational age at delivery, compared with non-obese women. Our aim was to quantify the indirect effect of pre-pregnancy obesity (body-mass-index, BMI, ≥30 m/kg2) on perinatal death mediated through differences in gestational age at delivery distribution.
Methods: The study included all singleton births at ≥20 weeks gestation in British Columbia, 2004-2017; pregnancy terminations and births missing information on BMI were excluded (28%). Data were obtained from the British Columbia Perinatal Database Registry. Logistic regression models were used to estimate adjusted odds ratios (AOR) and 95% confidence intervals (CI). The proportion of the association between obesity and perinatal death that was mediated by gestational age at delivery (in weeks) was estimated by using natural effect models, adjusted for potential confounders.
Results: The study included 484,061 women with singleton births, of these, 60,040 (12.4%) were obese. Obese women had lower gestational age at delivery, e.g., preterm birth (<37 weeks) rates were 51.1 vs. 40.1 per 1000 total births per 1000 total births in obese vs non-obese women, respectively. Perinatal mortality was higher in obese women (66.5 vs. 44.7 per 1000 total births; AOR = 1.44, 95% CI 1.29-1.61). Mediation analysis showed that 64% of the association between obesity and perinatal death was mediated by gestational age at delivery (indirect effect AOR =1.27, 1.19-1.35, direct effect AOR=1.14, 95% CI 1.03-1.26). Assumptions required for mediation analysis with respect to causal inference are subject to assement through sensitivity analyses.
Conclusion: The association between pre-pregnancy obesity and perinatal death is partly mediated by lower gestational age distribution among obese women. Under specific assumptions, the results suggest that prematurity is implicated in aabout 64% of obesity-related causes of perinatal death.