Main findings:
Placental abruption (PA) occurs in 1-2% of pregnancies and incurs considerable maternal and perinatal morbidity and mortality. While the majority of research underlying the causes of PA has been directed at evaluating environmental risk factors (e.g. PROM, smoking, prior PA, hypertension, history of cesarean delivery), recent studies have assessed genetic causes. 8–16 A pivotal step in the distinction between environmental and genetic causes for PA is the estimation of familial risk in a population. We estimated 18-20% as the inherited odds for PA in FDRs, and 9% and 0-1% respectively, for SDRs and TDRs. We noted an elevated odds of PA for all degrees of relation for the highest risk individuals, or individuals who experienced two or more PAs.
With use of the ego-driven familial analysis, known clinical risk factors such as PROM, smoking, and hypertension were adjusted for, which diminished the estimated increased odds of PA for an individual towards the null (16% vs. 20% with the relative-driven analysis). We see that these environmental risk factors outweigh genetic heritability at the second- and third-degree relation level as those estimations were not statistically significant.