Thrombophilias and adverse pregnancy outcomes: results from the Danish National Birth Cohort

Summary.  Background:  Inherited thrombophilias have inconsistently been linked to adverse pregnancy outcomes. Differences in study design, size and population could explain this heterogeneity. Objective:  The aim of the present study was to evaluate if factor (F)V Leiden G1691A, prothrombin mutation G20210A (PTM) and methylenetetrahydrofolate reductase C677T (MTHFR) increased the risk of severe preeclampsia, fetal growth restriction, very preterm delivery, placental abruption and a composite of these outcomes also including stillbirth. Patients and methods:  In a nested case–cohort study of pregnant women in Denmark, we genotyped 2032 cases and 1851 random controls. Each of the medical records of the cases was validated. We calculated both genomic and allelic models, and present both models. We also performed sensitivity analyses adjusting for parity, age, smoking, body mass index and socioeconomic status. Results:  In the allelic models, FV Leiden increased the risk of the composite outcome (odds ratio [OR] 1.4, 95% confidence interval [CI] 1.1–1.8), severe preeclampsia (OR 1.6, 95% CI 1.1–2.4), fetal growth restriction (OR 1.4, 95% CI 1.1–1.8) and placental abruption (OR=1.7 (95% CI 1.2–2.4). In the sensitivity analyses, adjustment diminished these estimates slightly. PTM was not significantly associated with any of the outcomes, and MTHFR was only significantly associated with severe preeclampsia (OR 1.3, 95% CI 1.1–1.6). Conclusion:  FV Leiden predisposes to adverse pregnancy outcomes in a setting of Scandinavian women.