Incidence of Preeclampsia: Risk Factors and Outcomes Associated with Early- Versus Late-onset Disease

Objective: The population-based incidence of early-onset (<34 weeks) and late-onset preeclampsia (≥34 weeks) has not been adequately studied. We examined the gestational age-specific incidence of preeclampsia onset and identified the associated risk factors and birth outcomes.

Study Design: All singleton deliveries in Washington State, 2003-2008 (n = 456,668), were included, and preeclampsia onset was determined from hospital records linked to birth certificates. Cox and logistic regression models were used to obtain adjusted hazard ratios and odds ratios (AORs) for risk factors and birth outcomes, respectively.

Results: The overall preeclampsia rate was 3.1% and the incidence increased sharply with gestation; early- and late-onset preeclampsia rates were 0.38% and 2.72%, respectively. Among women with early-onset preeclampsia, 12% delivered at a gestation of 34 weeks or longer. Risk/protective factors common to both diseases included older maternal age, Hispanic and Native-American race, smoking, unmarried status, and male fetus. African-American race, chronic hypertension, and congenital anomalies were more strongly associated with early-onset preeclampsia, whereas younger maternal age, nulliparity, and diabetes mellitus were more strongly associated with late-onset disease. Early- but not late-onset preeclampsia conferred a high risk of fetal death (AOR, 5.8; 95% confidence interval [CI], 4.0-8.3 vs AOR, 1.3; 95% CI, 0.8-2.0, respectively). The AOR for perinatal death/severe neonatal morbidity was 16.4 (95% CI, 14.5-18.6) in early-onset and 2.0 (95% CI, 1.8-2.3) in late-onset preeclampsia.

Conclusion: Early- and late-onset preeclampsia shares some etiological features, differ with regard to several risk factors, and lead to different outcomes. The 2 preeclampsia types should be treated as distinct entities from an etiological and prognostic standpoint.