An anembryonic gestation (aka blighted ovum) is a pregnancy in which a visible embryo never develops within a normal-appearing gestational sac, which likely occurs as a result of early embryonic death with continued development of the trophoblast. When small, the sac cannot be distinguished from the early normal pregnancy, as there may be a yolk sac, though a fetal pole is not seen.

This is one of the causes of miscarriage of a pregnancy.

For diagnosis, the sac must be of sufficient size that the absence of normal embryonic elements is established.

A pregnancy is anembryonic if a transvaginal ultrasound reveals a sac with a mean gestational sac diameter (MGD) greater than 13mm and no yolk sac, or a MGD >18 mm with no embryo.

Many centers offer mothers a follow-up ultrasound 10 days later to verify diagnosis.

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Anembryonic gestation