Characteristics of eclampsia not preceded by hypertensive disorders of pregnancy: a case control study

Eclampsia is traditionally considered a complication of hypertensive disorders of pregnancy (HDP). However, atypical cases occur without preceding HDP, and their pathophysiological mechanisms remain unclear. This study aimed to compare the clinical features of eclampsia with and without prior HDP diagnosis.

We retrospectively analyzed 31 singleton pregnancies with eclampsia diagnosed at nine Japanese perinatal centers between 2007 and 2023. Cases were classified into two groups: eclampsia preceded by HDP (n = 14) and eclampsia not preceded by HDP (n = 17). Clinical characteristics, laboratory findings, and perinatal outcomes were compared.

Of the 31 cases of eclampsia, 17 (57%) were not preceded by HDP, while the remaining cases had been diagnosed with HDP prior to the onset of eclampsia. In the eclampsia not preceded by HDP group, compared to the eclampsia preceded by HDP group, the BMI was significantly lower (22.07 ± 2.05 vs. 25.60 ± 6.19 kg/m², P = 0.047), the gestational week at delivery was significantly later (median 40.0 [32.0-41.0] vs. 37.5 [26.0-41.0] weeks, P = 0.020), and the proportion of male neonates was significantly higher (58.8% vs. 14.3%, P = 0.024). When comparing the onset periods-antepartum, intrapartum, and postpartum-the eclampsia not preceded by HDP group exhibited the highest number of cases during the intrapartum period, with 9 cases, while the eclampsia preceded by HDP group showed the highest number during the postpartum period, with 8 cases. Furthermore, in the eclampsia not preceded by HDP group, the white blood cell count was significantly higher immediately after onset (20,626 ± 7,956 vs. 14,687 ± 5,664 /μL, P = 0.039).

Atypical eclampsia without preceding HDP shows distinct clinical features, including later gestational age at onset, higher intrapartum incidence, and elevated inflammatory markers. These findings suggest a need for further investigation into alternative pathophysiological mechanisms and tailored clinical strategies for such cases.