Medline ® Abstracts for References 11,12

OBJECTIVE: To estimate the magnitude of associations of acute and chronic processes with abruption in preterm and term gestations.

METHODS: A retrospective cohort study was performed using data on women that delivered singleton live births and stillbirths at 20 or more weeks of gestation in the United States, 1995-2002 (n = 30,378,902). Rates of 1) acute-inflammation-associated clinical conditions (premature rupture of membranes and intrauterine infection); 2) chronic processes associated with vascular dysfunction or chronic inflammation (chronic and pregnancy-induced hypertension, preexisting or gestational diabetes, small for gestational age, and maternal smoking); and 3) both acute and chronic processes, were examined among women with and without abruption. Rates were examined separately among preterm (<37 weeks) and term births, with adjustment for confounders. Relative risk (RR) for aforementioned groups in relation to abruption was derived from multivariate logistic regression models after adjusting for potential confounders.

RESULTS: At preterm gestation, the rates of acute-inflammation-associated conditions were higher among women with than without abruption (12.0% compared with 10.2%; RR 1.38, 95% confidence interval [CI]1.34-1.42). At term, acute-inflammation-associated conditions were present in 4.2% and 3.3% of births with and without abruption, respectively (RR 1.39, 95% CI 1.33-1.45). At preterm gestation, the rates of chronic processes were 43.9% and 30.0% among women with and without abruption, respectively (RR 1.87, 95% CI 1.85-1.90). At term, the corresponding rates of chronic processes were 41.0% and 22.7%, respectively (RR 2.37, 95% CI 2.34-2.41). Association between both acute and chronic processes and abruption are similar to those of acute-inflammation-associated conditions.

CONCLUSION: Among women with placental abruption, conditions associated with acute inflammation are more prevalent at preterm than term gestations, whereas chronic processes are present throughout gestation.

LEVEL OF EVIDENCE: II-2.

BACKGROUND: Clinicians widely regard placental abruption as an acute event, though accumulating data point towards abruption being the end-result of chronic processes early in pregnancy, and perhaps even extending to conception. The Collaborative Perinatal Project was a prospective cohort study performed from 1959 to 1966 in the United States. Since enrolled pregnancies were managed without the biases created by modern perinatal surveillance and interventions, the natural history of disease in these data is ideal to study obstetrical complications such as placental abruption.

OBJECTIVE: We assessed the associations versus contributions of the clinical feature of early gestational vaginal bleeding and histologic lesions (chronic and acute) with placental abruption.

STUDY DESIGN: Women enrolled in the Collaborative Perinatal Project (1959-1966) were used, restricting the analysis to those that delivered singleton births (n=46,364). Risksof placental abruption were compared between women with and without vaginal bleeding at<20 weeks gestation. We also examined the relationships between placental abruption and chronic and acute histologic lesions, including infarcts, decidual necrosis, presence of macrophages in the decidua, amnion or chorion, and neutrophil infiltration in the amnion, chorion, placental surface, and umbilical vein.

RESULTS: Any episode of vaginal bleeding at<20 weeks in pregnancy conferred an increased risk of placental abruption (adjusted relative risk (RR) 1.6, 95% confidence interval (CI) 1.3, 1.8). The greatest risk occurred with bleeding in both the first two trimesters (RR 3.1, 95% CI 2.3, 4.1). The presence of histologic lesions in the placenta, cord and membranes similarly carried an increased risk of placental abruption, even in the absence of vaginal bleeding. The risk of abruption was, however, highest in the presence of both histologic lesions and vaginal bleeding early in pregnancy.

CONCLUSION: Vaginal bleeding early in pregnancy and histologic lesions of the placenta, umbilical cord, and membranes are associated with increased risk of placental abruption in later pregnancy. However, the increased risk associated with placental lesions, especially chronic inflammatory lesions, even in the absence of early vaginal bleeding, suggests that prolonged inflammation may be implicated in placental abruption.