Preterm preeclampsia as an independent risk factor for thromboembolism in a large national cohort

Abstract

BackgroundPreterm preeclampsia, a product of vascular dysfunction, is associated with prolonged hospital admission and proteinuria, significant risk factors for thromboembolism in pregnancy. The risk of thromboembolism in preterm preeclampsia warrants further investigation. ObjectivesTo determine the relationship between preterm preeclampsia and thromboembolic risk. We hypothesize that preterm preeclampsia is an independent risk factor for thromboembolism in pregnancy. Study DesignThis is a retrospective cohort study using the National Inpatient Sample database via HCUP-AHRQ from 2017-2019. All subjects with an ICD-10 code for pregnancy or peripartum encounter were included. Subjects were excluded if gestational age at delivery was less than 20 weeks or if they had a history of thromboembolism, inherited thrombophilia, or antiphospholipid syndrome. Patients with preterm (delivered less than 37 weeks) preeclampsia and term (delivered 37 weeks or greater) preeclampsia were compared to those without preeclampsia. The primary outcome was a composite of any thromboembolic event, including pulmonary embolism, deep vein thrombosis, cerebral thrombosis/transient ischemic attack (TIA), or other thromboses. The secondary outcomes were rates of each individual type of thromboembolic event. The groups were compared via analysis of variance, chi-squared, and logistic regression analyses. The logistic regression included those variables that differed between groups with p<0.05. ResultsOf individuals in the database more than 2.2 million met inclusion criteria. A total of 56,446 (2.7%) had preterm preeclampsia and 86,152 (6.7%) had term preeclampsia. Those with preterm preeclampsia were more likely to be older, identify as non-Hispanic black, be obese, have chronic hypertension among other chronic diseases, and be in the lowest quartile of income (p<0.001). Among patients with preterm preeclampsia, 0.32% experienced thromboembolism while those with term preeclampsia and without preeclampsia experienced thromboembolism 0.10% and 0.09%, respectively. After controlling for confounders that differed between groups with p<0.05, preterm preeclampsia remained independently associated with any thromboembolic event (aOR 2.21 95%CI 1.84-2.65) as well as each individual type of thromboembolism. Term preeclampsia was not associated with an increased risk of thromboembolism (aOR 1.18, 95%CI 0.94-1.48). ConclusionPreterm preeclampsia is independently associated with an increased risk of thromboembolic events.