Page 21 - SONO 260 THE FIRST TRIMESTER
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The first structure seen with sonography within the gestational sac is the secondary yolk sac.
It appears within the gestational sac as a round, anechoic structure surrounded by a thin, echogenic rim.
It is located within the chorionic cavity, between the amnion and chorion.
This cavity may also be referred to as the extraembryonic coelom or extracelomic space.
¡ When concerned about an ectopic pregnancy, visualization of a yolk sac within the gestational sac virtually excludes an ectopic
pregnancy.
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