[Determining implantation time frame of the trophoblast by hCG level monitoring].

Although the implantation of a human trophoblast cannot be directly observed, in-vitro fertilization permits examination of the factors accompanying the nidation of the trophoblast. Against this background, the question arises: at what point in time does the nidation of the human embryo take place in the endometrium of the uterus? In this study, we investigated 104 pregnancies which had resulted from in-vitro fertilization. The course curves of the HCG serum concentration were drawn up and then set in relation to the course of the pregnancy. By means of a regression analysis, we established the time point at which nidation occurred. In pregnancies carried through to delivery, the implantation 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 percentile). In the case of abortions, the median is 7,0 days (after follicle puncture), and for extra-uterine pregnancies it is 8.1 days (after follicle puncture). This shows that implantations in pathological pregnancies take place at a larger point in time.