Genetic background and risk of postpartum haemorrhage: results from an Italian cohort of 3219 women.

Postpartum haemorrhage (PPH) is a leading cause of maternal mortality, particularly in the developing countries, and of severe maternal morbidity worldwide. To investigate the impact of genetic influences on postpartum haemorrhage, in association with maternal and intrapartum risk factors, using a candidate gene approach. All women (n = 6694) who underwent a vaginal delivery at the Obstetric Unit of a large University hospital in Milan (Italy) between July 2007 and September 2009 were enrolled. The first consecutive 3219 women entered the genetic study. Postpartum haemorrhage was defined as ≥500 mL blood loss. Eight functional polymorphisms in seven candidate genes were chosen because of their potential role in predisposing to or protecting from haemorrhagic conditions: tissue factor (F3), factor V (F5), tissue factor pathway inhibitor (TFPI), platelet glycoprotein Ia/IIa (ITGA2), prothrombin (F2), platelet glycoproteins Ibα (GP1BA) and angiotensin-converting enzyme (ACE). After correction for the already known PPH risk factors, only the promoter polymorphism of the tissue factor gene (F3 -603A>G) showed a significant association with PPH, the G allele exerting a protective effect (P = 0.00053; OR = 0.79, 95% CI = 0.69-0.90). The protective effect against PPH of the TF -603A>G polymorphism is biologically plausible since the G allele is associated with an increased protein expression and Tissue Factor is strongly represented in the placenta at term, particularly in decidual cells of maternal origin.