Placental abruption in each hypertensive disorders of pregnancy phenotype: a retrospective cohort study using a national inpatient database in Japan.

We designed a retrospective cohort study using the Diagnosis Procedure Combination database, a national inpatient database for acute-care inpatients in Japan, to examine whether recent global diagnostic criteria for preeclampsia, phenotypes of hypertensive disorders of pregnancy (HDP) and features of the disease are useful as predictors of placental abruption and whether other risk factors are associated with the onset of placental abruption. A total of 85,858 hospitalized patients with a diagnosis of HDP who gave birth during hospitalization between July 2010 and March 2018 were included in this study. We examined the associations between the occurrence of placental abruption after hospitalization and several factors, including gestational age (GA) at placental abruption onset, HDP subtypes, GA on admission, maternal age, body mass index, smoking, multiple pregnancy, prelabor rupture of membranes, diabetes mellitus, emergency admission by ambulance, and consciousness, using a multivariate logistic regression analysis. Placental abruption occurred in 541 patients (0.63%) after hospital admission, and the occurrence increased acutely after 32 weeks GA. A decrease in abruption was significantly associated with maternal BMI on admission (≥30 kg/m2; odds ratio [OR], 0.54; 95% confidence interval [CI], 0.41-0.70) and multiple pregnancy (OR, 0.29; 95% CI, 0.18-0.46). An increase in abruption was associated with earlier GA on admission (<34 weeks' GA; OR, 3.77; 95% CI, 3.13-4.53) and emergency admission by ambulance (OR, 1.34; 95% CI, 1.09-1.65). Individual features of severe PE showed no significant associations with the occurrence of abruption. In conclusion, HDP at an earlier GA was suggested to be a risk factor for placental abruption, and we recommend hospitalization and careful management of such patients to improve their prognosis.