Activated protein C resistance during in vitro fertilization treatment

Acquired resistance to the anticoagulant action of activated protein C (APC ) has been proposed To explain the increased risk of venous thrombosis asso ciated with pregnancy, hormone replacement therapy and the use of oral cont raceptives, Tn this study, we have investigated whether the hormonal change s induced during in vitro fertilization (IVF) treatment are also associated with acquired APC resistance. Twenty-nine women, who were planned for an I VF cycle, donated blood at four time points during treatment, i.e. at basel ine, down-regulation, hyperstimulation and luteal support. Tn the plasma sa mples, APC sensitivity ratios (APCsr) and the levels of progesteron and est radiol were measured. The changes in plasma concentrations of hormones were in accordance with literature. The APCsr increased significantly during hy perstimulation and remained high during luteal support. The extent of APC r esistance occurring during IVF treatment was comparable to that observed du ring the use of second generation OC and was less pronounced than that occu rring during pregnancy. The change in estradiol between baseline and hypers timulation correlated with the change in APCsr. Although this suggests that plasma estrogen levels are an important determinant For acquired APC resis tance. it remains to be established a which plasma proteins are responsible for estrogen-induced APC resistance. (C) 2001 Elsevier Science Ireland Ltd . All rights reserved.