Pre-pregnancy body mass index and other risk factors for early- and late-onset hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome: A population-based retrospective cohort study.
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abstract
Background: Obesity increases risk of pre-eclampsia, but the
association with hemolysis, elevated liver enzymes, and low platelets
(HELLP) syndrome is understudied. Objective: To examine the
association between pre-pregnancy body-mass-index (BMI) and HELLP
syndrome, including early- vs. late-onset disease. Study
Design: A retrospective cohort study, population-based data.
Setting: British Columbia (BC), Canada, 2008/09-2019/20.
Population: All pregnancies resulting in live births or
stillbirths at ≥20 weeks’ gestation. Methods: BMI categories
(kg/m ) included: 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 assess the
associations between risk factors (BMI and, e.g., maternal age, parity)
and early- vs late-onset HELLP syndrome. Main outcome measures:
HELLP syndrome. Results: The rates of HELLP syndrome per 1000
women were 2.8 overall (1,116 per 391,941 women), and 1.9, 2.5, 3.2 and
4.0 in underweight, normal BMI, overweight and obese categories,
respectively. Overall, gestational age-specific rates increased with
pre-pregnancy BMI. Adjusted hazard ratio [AHR] was 2.24 for
early-onset (95% confidence interval [CI] 1.65-3.04) vs. AHR 1.48
(95% CI 1.23-1.80) for late-onset HELLP syndrome (p-value for
interaction 0.025). Chronic hypertension, multiple gestation, hemorrhage
(<20 weeks’ gestation and antepartum) also showed differing
AHRs between early- vs. late-onset HELLP. Conclusions:
Pre-pregnancy BMI is positively associated with HELLP syndrome and the
association is stronger with early-onset HELLP syndrome. Associations
with early- and late-onset HELLP syndrome differed for some risk
factors, suggesting possible differences in etiologic mechanisms.
