<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 can not 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>
<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 can not 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
gestational sac but no yolk sac and embryo
blighted ovum or anembryonic gestation
blighted ovum or anembryonic gestation