The impact of the definition of preeclampsia on disease diagnosis and outcomes: a retrospective cohort study

Abstract

BACKGROUND:The diagnostic criteria for preeclampsia have evolved from the traditional definition of de novo hypertension and proteinuria to a broader definition of hypertension with evidence of end-organ dysfunction. While this change is endorsed by various societies such as the International Society for the study of Hypertension in Pregnancy (ISSHP) and the American College of Obstetricians and Gynecologists (ACOG), there remains controversy with regards to the implementation of broader definitions, and the most appropriate definition of end-organ dysfunction. OBJECTIVES:1) To assess the impact of different diagnostic criteria for preeclampsia on rates of disease diagnosis, disease severity and adverse outcomes. 2) To identify associations between each component of the different diagnostic criteria and adverse pregnancy outcomes. STUDY DESIGN:We performed a retrospective cohort study of singleton pregnancies at Monash Health between 1/1/2016 and 7/31/2018. Within this population, all cases of gestational hypertension and preeclampsia were reclassified according to the ISSHP 2001, ACOG 2018 and ISSHP 2018 criteria. Differences in incidence of preeclampsia, and maternal and perinatal outcomes were compared between the ISSHP 2001 group and the extra cases identified by ACOG 2018 and ISSHP 2018. Outcomes assessed included biochemical markers of preeclampsia, a composite of adverse maternal outcomes and a composite of adverse perinatal outcomes. Multiple logistic regression analysis was also performed to assess each component of the ACOG 2018 and ISSHP 2018 criteria and their associations with adverse maternal and perinatal outcomes. RESULTS:Of 22,094 pregnancies, 751 (3.4%) women had preeclampsia as defined by any of the three criteria. Compared to ISSHP 2001, the ACOG 2018 criteria identified an extra 42 women (n=654 vs n=696, 6.4% relative increase) with preeclampsia, and ISSHP 2018 identified an extra 97 women (n=654 vs n=751, 14.8% relative increase). The additional women identified by ISSHP 2018 exhibited a milder form of disease with lower rates of severe hypertension (62.4% vs 44.3%, p<0.01), magnesium sulfate use (11.9% vs 4.1%, p<0.05), and a trend towards lower rates of adverse maternal outcomes (9.8% vs 4.1%). These women also delivered at a later gestation, and their babies had a lower number of neonatal intensive care unit admissions and adverse perinatal outcomes. Objective features such as fetal growth restriction, thrombocytopenia, renal and liver impairment, and proteinuria were associated with an increased risk of adverse maternal and perinatal outcomes, whereas subjective neurological features demonstrated poorer associations. CONCLUSION:Implementation of broader definitions of preeclampsia will result in an increased incidence of disease diagnosis. However, since women that exclusively fulfil the new criteria have a milder phenotype of the disease, it remains uncertain whether this will translate to improved outcomes.