Empty Gestational Sac

Definition - What does Empty Gestational Sac mean?

An empty gestational sac is a cavity contained within the uterus of a pregnant female, which does not contain a living embryo. An empty gestational sac usually occurs due to a blighted ovum, which is a fertilized egg that has been capable of implanting itself within the uterus but fails to progress to the stage of an embryo.

An empty gestational sac is also referred to as a blighted ovum or an anembryonic pregnancy (i.e. a pregnancy with no embryo).

FertilitySmarts explains Empty Gestational Sac

The presence of a gestational sac (as detected on an ultrasound) indicates the start of pregnancy. In fact, it is the only marker of pregnancy until the identification of an embryo. A gestational sac can be detected on a transvaginal scan when it measures as little as 2 to 3 mm in diameter at around 5 weeks from the LMP. It evolves to enclose an embryo by around 5 to 6 weeks of pregnancy.

Doctors measure the mean diameter of the gestational sac to determine how far along a woman is in her pregnancy as dated from the first day of her last menstrual period (LMP). More importantly, the mean diameter of the sac is used to assess the presence of a viable embryo. A pregnancy sac is labeled as being "empty" when it approaches a mean diameter of 25 mm by the 7th week but the transvaginal ultrasound fails to identify a fetal pole (embryo), signaling a non-viable pregnancy, which will abort on its own.

In short, an empty gestational sac helps predict early pregnancy loss, which is defined as miscarriage occurring before or at 12 weeks from the first day of the LMP.

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