EP12.08: Risk of superimposed pre‐eclampsia and adverse outcomes in pregnant women with chronic hypertension

To evaluate the rates of adverse maternal and perinatal outcomes in pregnant women with chronic hypertension (CH) compared to normotensive controls, and to assess the risk factors for the occurrence of superimposed pre-eclampsia (PE). Retrospective cohort study encompassing all births over 20 weeks of gestation between 2014 and 2018 in the state of Victoria, Australia. 390,282 births were analysed, being 98.5% singletons and 96.0% spontaneously conceived. CH, PE and eclampsia occurred in 1.24%, 2.56% and 0.08% of pregnant women, respectively. Superimposed PE occurred in 0.25% of the overall population and 20.5% of CH patients. Rates of placental abruption, acute pulmonary edema (APE), stroke, thromboembolic event, disseminated intravascular coagulation (DIC) and thrombocytopenia were all below 0.5%. Stillbirth and neonatal death rates were 0.42% and 0.2%, respectively. The most prevalent perinatal complications were respiratory distress (4.85%) and neonatal sepsis (1.30%). Compared to controls, pregnant women with CH presented higher rates (p < 0.05 for all) of APE (0.02% x 0%, odds ratio (OR) 20.1, 95% CI 2.3-178.9), PE (20.5% x 2.33%, OR 10.8, 95% CI 10.1-11.6), eclampsia (0.7% x 0.07%, OR 9.7, 95% CI 6.8-13.8), DIC (0.02% x 0%, OR 7.3, 95% CI 0.9-56.2), abruption (0.93% x 0.51%, OR 1.8, 95% CI 1.4-2.5), and thrombosis (0.46% x 0.24%, OR 1.9, 95% CI 1.2-2.9). Perinatal complications were also increased, mainly necrotising enterocolitis (OR 10.1) and retinopathy (OR 8.5). Significant risk factor for superimposed PE were multiple pregnancies (OR 2.4, 95% CI 1.6-3.4) and being attended on the public health sector (OR 1.9. 95% CI 1.5-2.3), whereas higher socioeconomic status quintiles showed a tendency to decreased risk (OR 0.8. 95% CI 0.6-1.0). CH results in increased rates of maternal and perinatal complications. Superimposed PE is frequent and knowledge of risk factors may be important for patient counselling.