Introduction: Abnormal yolk sac size is associated with fetal miscarriage. This is a case report of two pregnancies with abnormal yolk sacs.
Materials and methods: In one case, a twofold sac was found; in the other case, the yolk sac was not of spherical form.
Conclusion: Currently available publications demonstrate a correlation between abnormal yolk sac size and miscarriage. However, in both cases a trisomy was confirmed. It should therefore be discussed whether form and size of the yolk sac could be a marker for chromosomal abnormalities of the fetus.