The relation between depth of trophoblastic invasion and beta-HCG levels in tubal pregnancies

beta-HCG (human chorionic gonadotropin) values of over 2500 I.U./l are associated with higher failure rates for therapy with prostaglandin F2 alpha in tubal pregnancies. The purpose of our study was to ascertain if the 2500 I.U./l limit correlates with histopathology. We therefore compared the pre-operative beta-HCG-values and intraluminal and extraluminal trophoblast growth in tubal pregnancy. Purely intraluminal trophoblast was significantly more frequent in patients of group I (beta-HCG < 2500 I.U./l), while group II patients (beta-HCG > 2500 I.U./l) almost exclusively had extraluminal growth (P = 0.0045). Since the efficacy of prostaglandin F2 alpha therapy depends on intact tubal musculature the correlation of the beta-HCG threshold level with histopathologic findings may explain the high failure rate in patients with beta-HCG values above 2500 I.U./l.