<Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> A blighted ovum or anembryonic gestation (anembryonic pregnancy) is a pregnancy in which the embryo never develops or develops and is reabsorbed . It typically results in a miscarriage . In a normal pregnancy, an embryo would be visible on an ultrasound by six weeks after the woman's last menstrual period . Anembryonic gestation is one of the causes of miscarriage of a pregnancy . </P> <P> A blighted ovum or anembryonic gestation is characterized by a normal - appearing gestational sac, but the absence of an embryo . It 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 . For diagnosis, the sac must be of sufficient size that the absence of normal embryonic elements is established . The criteria depends on the type of ultrasound exam performed . A pregnancy is anembryonic if a transvaginal ultrasound reveals a sac with a mean gestational sac diameter (MGD) greater than 25 mm and no yolk sac, or an MGD> 25 mm with no embryo . Transabdominal imaging without transvaginal scanning may be sufficient for diagnosing early pregnancy failure when an embryo whose crown--rump length is 15 mm or more has no visible cardiac activity . </P>

Gestational sac but no yolk sac and embryo