The yolk sac is no longer visible on ultrasound beginning in which gestational week?

The yolk sac is no longer visible on ultrasound beginning in which gestational week?

• A. 8th week
• B. 10th week
• C. 12th week
• D. 14th week

Answer: (C)

The yolk sac is a temporary structure that nourishes the embryo early on and supports hematopoiesis until the placenta takes over. On ultrasound, it appears as a small round anechoic structure inside the gestational sac from about five weeks of gestation. As placental circulation becomes established, the yolk sac regresses and is typically too small to visualize after around the twelfth week. Therefore, the point at which it is no longer seen corresponds to the twelfth week of gestation. Earlier weeks would usually still show the yolk sac, while by later weeks it is already no longer visible.

The yolk sac is a temporary structure that nourishes the embryo early on and supports hematopoiesis until the placenta takes over. On ultrasound, it appears as a small round anechoic structure inside the gestational sac from about five weeks of gestation. As placental circulation becomes established, the yolk sac regresses and is typically too small to visualize after around the twelfth week. Therefore, the point at which it is no longer seen corresponds to the twelfth week of gestation. Earlier weeks would usually still show the yolk sac, while by later weeks it is already no longer visible.