Large Yolk Sac

Definition - What does Large Yolk Sac mean?

A large yolk sac is a yolk sac that is greater than 5-6 mm at 5-10 weeks of gestation. The yolk sac provides nourishment to a developing embryo until the placenta fully forms and takes over this function around the 8th week of pregnancy.

FertilitySmarts explains Large Yolk Sac

Because it appears so early in pregnancy, the yolk sac is an important indicator of embryo health at the early stage. As a result, it is closely examined on ultrasounds for size and shape. Evidence suggests that a large yolk sac is associated with an increased risk of spontaneous abortion (miscarriage).

Studies have found that there is a correlation between yolk sac abnormalities and early pregnancy loss. These abnormalities include irregularly-shaped yolk sacs, absent yolk sacs, and large yolk sacs. Large yolk sacs are frequently related to poor outcomes. Therefore, if a large yolk sac is seen on an ultrasound, follow-up imaging and close monitoring will likely be recommended.

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