system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
This is a sonogram demonstrating CRL of an 8 weeks fetus. The arrow in the field points to which of the following?
assistant
The correct answer is  The above USG image shows Anaechoic (black) gestational sac with an embryo and yolk sac (arrow). The yolk sac is seen as a small well-defined anaechoic structure in side the Gestational sac.Presence of yolk sac or fetal pole within the gestation sac confirms pregnancy. Double decidua sign of the gestational sac is due to the interface between the decidua and the chorion, which appears as two distinct layers of the wall of the gestation sac.