Large yolk sac

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A large yolk sac is one measuring >5-6 mm in pregnancies between a gestational age of 5-10 weeks. One study had shown that a yolk sac diameter of >5 mm can be associated with an increased risk of spontaneous miscarriage although few other authors have mentioned the existence of a very large yolk sac (e.g. around 8 mm) in a normal live pregnancy.

Abnormally large yolk sac may indicate a poor obstetric outcome and close follow-up with sonography is often recommended for these pregnancies.

Practical points

indeterminate abnormal yolk sac abnormality that should not be considered alone for the diagnosis of failed early pregnancy
follow-up ultrasonography at 7-14 days to assess the pregnancy for viability is generally appropriate