Severe placental abruption: clinical definition and associations with maternal complications

Placental abruption traditionally is defined as the premature separation of the implanted placenta before the delivery of the fetus. The existing clinical criteria of severity rely exclusively on fetal (fetal distress or fetal death) and maternal complications without consideration of neonatal or preterm delivery-related complications. However, two-thirds of abruption cases are accompanied by fetal or neonatal complications, including preterm delivery. A clinically meaningful classification for abruption therefore should include not only maternal complications but also adverse fetal and neonatal outcomes that include intrauterine growth restriction and preterm delivery.

The purpose of this study was to define severe placental abruption and to compare serious maternal morbidity profiles of such cases with all other cases of abruption (ie, mild abruption) and nonabruption cases.

We performed a retrospective cohort analysis using the Premier database of hospitalizations that resulted in singleton births in the United States between 2006 and 2012 (n = 27,796,465). Severe abruption was defined as abruption accompanied by at least 1 of the following events: maternal (disseminated intravascular coagulation, hypovolemic shock, blood transfusion, hysterectomy, renal failure, or in-hospital death), fetal (nonreassuring fetal status, intrauterine growth restriction, or fetal death), or neonatal (neonatal death, preterm delivery or small for gestational age) complications. Abruption cases that did not qualify as being severe were classified as mild abruption cases. The morbidity profile included amniotic fluid embolism, pulmonary edema, acute respiratory or heart failure, acute myocardial infarction, cardiomyopathy, puerperal cerebrovascular disorders, or coma. Associations were expressed as rate ratios with 95% confidence intervals that were derived from fitting log-linear Poisson regression models.

The overall prevalence rate of abruption was 9.6 per 1000, of which two-thirds of cases were classified as being severe (6.5 per 1000). Serious maternal complications occurred in 15.4, 33.3, and 141.7 per 10,000 among nonabruption cases and mild and severe abruption cases, respectively. In comparison with no abruption, the rate ratio for serious maternal complications were 1.52 (95% confidence interval, 1.35-1.72) and 4.29 (95% confidence interval, 4.11-4.47) in women with mild and severe placental abruption, respectively. Rate ratios for the individual complications were 2- to 7-fold higher among severe abruption cases. Furthermore, the rate ratios for serious maternal complications among severe abruption cases compared with mild abruption cases was 3.47 (95% confidence interval, 3.05-3.95). This association was considerably stronger for virtually all maternal complications among cases with severe abruption compared with mild abruption. Annual rates of mild and severe abruption were fairly constant during the study period. Although the maternal complication rate among non-abruption births was stable from 2006-2012, the rate of complications among mild abruption cases dropped from 2006-2008 and then leveled off thereafter. In contrast, the rate of serious complications among severe abruption cases remained fairly stable from 2006-2010 and increased sharply thereafter.

Severe abruption was associated with a distinctively higher morbidity risk profile compared with the other 2 groups. The clinical characteristics and morbidity profile of mild abruption were more similar to those of women without an abruption. These findings suggest that the definition of severe placental abruption based on the proposed specific criteria is clinically relevant and may facilitate epidemiologic and genetic research.