[Clinical significance of detection time and site of early gestational sac by ultrasonography].

Ultrasonography was used to determine not only the shape but also the appearance time and site of GS before the formation of the embryo. These factors were analysed for their clinical significance in association with early GS. The following results were obtained. 1. GS with diameters of 2 < or = approximately < or = 4 mm (abr. EGS) were found at 17-25 postovulatory days (gestational age: GA 4w2d-5w3d) in the ovulation presumed group. EGS was detected at GA 4w2d-7w5d in the normal menstrual group and 17.6% of cases were detected at GA 6w or later. 2. 95.3% of EGS were found in the upper 2/3 of the uterine cavity, while only 4.6% were found in the lower 1/3. This difference in incidence was significant. When EGS was found in the lower uterine segment at GA 6w or later, the abortion rate was very high. 3. In cases where gestation continued to term, there was no difference between the ovulation presumed and normal menstrual groups in terms of various fetal conditions. When normal menstrual group cases where EGS was detected at GA 6w or later were compared with the members of the ovulation presumed group, gestation duration was prolonged in the former. From the above mentioned findings, it can be concluded that even in the early stage of gestation, there can be individual growth differences and that in cases with normal menstrual cycles, gestation can take place much later than the expected date of ovulation, and further that the diagnosis of intrauterine gestation should be postponed until the end of GA 6w. Many blighted ova are detected in cases where GS is found at GA 6w or later, but when gestation is carried to term, no fetal growth abnormalities are found. The ideal nidation site is the endometrium near the fundus and when nidation takes place in the lower segment, the incidence of abortion or placenta previa is very high.