Empty gestational sacs can be due to a number of causes: anembryonic pregnancy (also known as blighted ovum ) early pregnancy (intrauterine): by 5.5 weeks gestational age, a yolk sac should be identifiable by transvaginal ultrasound, The gestational sac (GS) is the first sign of early pregnancy on ultrasound and can be seen with endovaginal ultrasound at approximately 3-5 weeks gestation when the mean sac diameter (MSD ) would approximately measure 2-3 mm in diameter. A true gestational sac can be distinguished from a pseudogestational sac by noting:, A pseudogestational sac, also known as a pseudosac or intra-cavitary fluid, is the concept that a small amount of intrauterine fluid in the setting of a positive pregnancy test and abdominal pain could be erroneously interpreted as a true gestational sac in ectopic pregnancy.
What Does an Empty Gestational Sac Mean? An embryo is usually seen within the gestational sac by 6 weeks gestation. One of the more common types of miscarriages—known as an an embryonic pregnancy, empty sac, or blighted ovum—happens when a gestational sac does not contain an embryo. In other words, an embryo failed to develop.
Yolk sac is the first anatomical structure identified within the gestational sac.It plays a critical role in embryonal development by providing nutrients, serving as the site of initial hematopoiesis, providing endocrine, metabolic and immunological functions and contributing to the development of fetal gastrointestinal and reproductive systems 2.
MSD of >25 mm with absent fetal pole indicates pregnancy failure ( missed miscarriage ) an MSD of 16-24 mm without an embryo is suspicious for pregnancy failure, but not definitive. when the MSD measures 8 mm a yolk sac should be visible, however ,lack of a yolk sac is not an indication of pregnancy failure.
The gestational sac is the implantation product that occurs in the uterus on approximately day 21. At that time the blastocyst is approximately 0.1 mm in size and cannot be seen by US. Normal sacs become visible when they reach 2 to 3 mm. Measurements: Mean sac diameter (MSD) =.
The typical sonographic appearance of anembryonic pregnancy is a large, empty gestational sac that does not demonstrate a yolk sac, an amnion, or an embryo ( Figure 50-4 ). The MSD increases by 1.13 mm/day in a normal gestation, but the growth rate of an abnormal sac is only 0.70 mm/day.
