Clinical risk factors and protective factors of preeclampsia in China

The pathophysiology of preeclampsia remains unclear. The identification of risk factors and protective factors may help elucidate the pathophysiologic basis of preeclampsia and improve its prediction. A cross-sectional survey of all deliveries in 39 hospitals across 14 provinces in mainland China from January 1 to December 31, 2011 was conducted to evaluate risk factors and protective factors for preeclampsia. The incidence rate of preeclampsia was 3.7% (4137/110, 926). Multivariate logistic analysis revealed advanced maternal age (aOR=2.058; 95% CI: (1.894–2.235)), chronic hypertension (aOR=8.391; 95% CI: (7.352–9.576)], obesity (aOR=3.761; 95% CI: (3.487–4.056)), GDM/DM (aOR=1.656 (1.479–1.855)), multiple pregnancies (aOR=1.491; 95% CI: (1.283–1.735)), anemia (aOR=1.253; 95% CI: (1.110–1.414)) and blood type AB (aOR=1.134; 95% CI: (1.006–1.279)) as independent risk factors. The protective factors included placenta previa (aOR=0.401; 95% CI: 0.296–0.543) and blood type A (aOR=0.901; 95% CI: 0.829–0.980). The prevalence of obstetric complications associated with preeclampsia was higher, including preterm birth [aOR=8.542; 95% CI: (7.985–9.137)], FGR [aOR= 5.020; 95% CI: (4.635–5.437)], placental abruption [aOR=3.453; 95% CI: (2.777–4.293)] and oligohydramnios [aOR=1.520; 95% CI: (1.306–1.768)]. The results revealed that chronic hypertension and obesity were more strongly associated with early-onset preeclampsia; whereas multiple gestation, maternal age, GDM/DM, and anemia were more strongly associated with late-onset preeclampsia. Placenta previa was a protective factor against preeclampsia (PE), particularly early-onset PE. Early-onset PE was more likely to cause placental abruption, FGR and oligohydramnios than late-onset PE. Our study revealed different epidemiological features between early-onset and late-onset PE, suggesting the involvement of different mechanisms, which requires further research.