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1.2.2.2 Development of corpora lutea during the estrous cycle and in early pregnancy

The site of the development of a corpus luteura can already be recognized by its intense ultrasonic echogen-icity within the first 24 hours after ovulation (Fig. 1.24). In some cases this site can even be detected within minutes after ovulation (Ginther and Pierson 1984 a, Kahn and Leidl 1987 b). These intense reflections originate from the hemorrhage into the follicular lumen which occurs after ovulation (Allen et al. 1987). The development of such hyperechoic areas at the sites of

former follicles can also be seen after iatrogenicaliy induced hemorrhages during follicular punctures (sce Chapter 1.2.1.3 and FIG. 1.19).

The hemorrhagic area of young corpora lutea re-mains very echoic for the first 3 to 4 days following ovu-lation (Palmer and Driancourt 1980). This hyper-echogenicity is only detectable for a short time after ovulation, because with the increasing proliferation of luteal cells in the area of the blood ciot it becomes less echoic. This process of luteinization usually progresses so rapidly, that large areas of the blood ciot are taken over by luteal tissue (Fig. 1.25).