Irregular yolk sac

Last revised by Jeremy Jones on 20 Sep 2021

An irregular yolk sac or an abnormally shaped yolk sac is an imaging feature that can be observed in early pregnancy scanning. It may be seen in up to 17% of early pregnancy scans 1. In contrast to an irregular gestational sac, the observation of an irregular yolk sac in not thought to correlate with pregnancy failure - low sensitivity but high specificity 2.

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

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