(1067) Pre-pregnancy body mass index and HELLP syndrome: A population-based retrospective cohort study

Objective: The association between pre-pregnancy body mass index (BMI) and HELLP (Hemolysis, Elevated Liver enzymes and Low Platelets) syndrome is understudied. We examined this association among women with early- and late-onset HELLP syndrome.

Study Design: This was a retrospective cohort study including all singleton live births and stillbirths in British Columbia (BC), Canada, 2008/09-2020/21. BMI categories included (kg/m²): underweight ( < 18.5), normal (18.5-24.9), overweight (25.0-29.9), and obese (≥ 30.0). Rates of early- and late-onset HELLP syndrome ( < 34 vs. ≥ 34 weeks, respectively) were calculated per 1000 ongoing pregnancies at 20 and 34 weeks’ gestation, respectively. Cox regression was used to adjust for confounders (e.g., nulliparity, maternal age, smoking and chronic conditions) and to assess differences in the association between BMI and early- vs late-onset HELLP syndrome (using an interaction between BMI and gestational age).

Results: This study included 391,939 women; the incidence of HELLP syndrome was 2.8 per 1000 total births (n = 1,116). BMI groups and their characteristics are shown in Table 1. The rates of HELLP syndrome in underweight, normal, overweight, and obese women were 1.9, 2.5, 3.2, and 4.0 per 1000 total births, respectively (Table 2). Increasing BMI was associated with an increase in risk of HELLP syndrome and this association was more prominent in early-onset HELLP syndrome. For instance, in early-onset HELLP, the adjusted hazard ratio (AHR) was 1.6 (95% CI 1.2-2.2) in overweight women and 2.3 (95% CI 1.7-3.1) in obese women. In contrast, in late-onset HELLP, the AHR was 1.2 (95% CI 1.1-1.5) in overweight women and 1.4 (95% CI 1.2-1.7) in obese women (Table 2). The interaction between BMI and gestational age was statistically significant in women with obesity (p < 0.01).

Conclusion: Pre-pregnancy BMI is positively associated with HELLP syndrome and the association is stronger with early-onset HELLP syndrome. This information is important for pre-pregnancy counselling and clinical management.