Objective: The objective of the study was to evaluate whether the association between low birthweight and placental abruption is mediated through preterm birth or restricted fetal growth and whether these associations were influenced by maternal thrombophilia status.
Study design: Data were derived from the New Jersey-Placental Abruption Study, an ongoing, multicenter, case-control study conducted in New Jersey since August 2002. Abruption cases (n = 156) were identified based on a clinical diagnosis, and controls (n = 170) were matched to cases based on parity and maternal race. Low birthweight (<2500 g) was stratified based on preterm birth (<37 weeks' gestation) and small for gestational age (birthweight < the 10th percentile for gestational age). Maternal thrombophilia assessment was based on serum evaluation (protein C and S deficiency, activated protein C resistance ratio, and anticardiolipin antibodies) as well as genetic polymorphisms (methylenetetrahydrofolate reductase, prothrombin gene, and factor V Leiden). Associations were expressed based on odds ratios (ORs) with 95% confidence interval (CI).
Results: Among abruption cases, 60.3% (n = 94) were low birthweight in comparison with 11.2% (n = 19) of controls (OR, 13.7; 95% CI, 7.4-25.2). Furthermore, placental abruption had a significantly increased association with preterm birth in both small for gestational age (OR, 17.4; 95% CI, 4.6-64.9) and appropriately grown fetuses (OR, 15.8; 95% CI, 8.4-29.8). However, the association between abruption and low birthweight were similar between women with and without thrombophilia.
Conclusion: The association between placental abruption and low birthweight is chiefly mediated through preterm birth, and this association does not appear to be modified by maternal thrombophilia status.