SERIAL HCG MEASUREMENTS TO DETERMINE THE IMPLANTATION WINDOW OF THE HUMAN TROPHOBLAST

Although the implantation of a human trophoblast cannot be directly ob served, in-vitro fertilization permits examination of the factors acco mpanying the nidation of the trophoblast. Against this background, the question arises: at what point in time does the nida tion of the huma n embryo take place in the endometrium of the uterus? In this study, w e investigated 104 pregnancies which had resulted from in-vitro fertil ization. The course curves of the HCG serum concentrations were drawn up and then set in relation to the course of the pregnancy. By means o f a regression analysis, we established the time point at which nidati on occurred. In pregnancies carried through to delivery, the implantat ion happens, on the median, 6.6 days after the follicle puncture. The implantation window lies between 5.9 and 7.5 days (25th to 75th percen tile). In the case of abortions, the median is 7,0 days (after follicl e puncture), and for extra-uterine pregnancies it is 8.1 days (after f ollicle puncture). This shows that implantations in pathological pregn ancies take place at a later point in time.