IMPACT OF TROPHOBLAST PENETRATION THROUGH THE BASAL MEMBRANE ON THE EFFICACY OF DRUG-THERAPY IN TUBAL PREGNANCIES

Concentrations of beta-human chorionic gonadotrophin (HCG) of 2500 IU/ l are generally considered to be maximal for successful drug therapy o f tubal pregnancies [instillation of prostaglandin-F-2 alpha (PGF(2 al pha)) or hyperosmolar glucose]. The purpose of our study was to ascert ain if there was an association between the significantly higher failu re rates above this threshold value and the histologically determined anatomopathological substratum. We therefore evaluated the impact of t rophoblast penetration through the basal membrane of the Fallopian tub e on the efficacy of drug therapy. Pre-operative serum beta-HCG concen trations were compared with the histologically determined trophoblast penetration, distinguishing between ectopic pregnancies with intra-lum inal growths up to the myosalpinx, and those with extra-luminal growth s going beyond the basal membrane and penetrating the myosalpinx. Basi c data were obtained from a group of patients who received primary sur gical treatment but it had never been the intention for them to receiv e drug therapy (independently of their initial beta-HCG values; group I, n = 43). These reference data were compared with the findings in pr eparations from another group of patients obtained during secondary su rgical intervention, performed to achieve final cure of tubal pregnanc y after failure of primary PGF(2 alpha) instillation (group II, n = 30 ). Group I patients showed a significantly higher rate of intra-lumina l trophoblast growths (P = 0.0001) at beta-HCG values <2500 IU/l; abov e this threshold value, extra-luminal spread was found significantly m ore often (P = 0.0001). In histological preparations from group II, ho wever, the number of extra-luminal growths was significantly higher ev en at low beta-HCG values (P = 0.007); at values above the threshold l evel, the distributions in the two groups were similar. These results suggest that drug therapy of tubal pregnancy becomes inefficient in tu bal pregnancies as soon as the trophoblast penetrates the basal membra ne of the Fallopian tube.