Correlation between grade III placenta and plasma antithrombin III activity in full term pregnancy

We evaluated whether the presence of a grade III placenta correlates with blood hypercoagulability in pregnancy between 37 and 39 weeks of gestation. The placenta was graded by ultrasound in 155 healthy full-term women and the plasma levels of antithrombin III (AT III) activity, thrombin-antithrombin complex (TAT) and D-dimer were correlated with each placental grade. AT III activity levels tended to decrease with advancing placental grade from I to III (p < 0.05). D-dimer showed the same tendency while TAT did not. The incidence of reduced AT III activity levels (<70%) in women with a grade III placenta was about twice those in women with a grade II or I placenta, and that of AT III <80% was 3-fold greater. We concluded that the presence of a grade III placenta in full-term pregnancies correlates with blood hypercoagulability.