What is an irregular gestational sac?

An irregular gestational sac as the name suggests is a gestational sac which does not have the well defined, regular borders of a normal gestational sac. It is an imaging feature related to a non-viable pregnancy.

What size should gestational sac be at 5 weeks?

The gestational sac may be recognized as early as 4 weeks and 1 day from the last menstrual period and should always be seen after 4 weeks and 4 days. Its diameter when first seen is about 2 mm and the normal sac increases in size to measure 5–6 mm at 5 weeks.

What does a gestational sac look like at 5 weeks?

At this stage, the only things you’ll likely see are the yolk sac and the gestational sac. It’s possible that the sonographer might be able to point out the embryo, which at this stage is likely a tiny white curled object. Surrounding the embryo is the yolk sac, which will look like a small white circle.

Can a gestational sac change shape?

Size, growth and shape of the gestational sac can vary and the mean sac diameter (MSD) is calculated as the arithmetic mean of its greatest sagittal, transverse and coronal planes. A MSD cutoff of ≥25 mm with no embryo is diagnostic of failed pregnancy (Figure 4.6).

What does an irregular yolk sac mean?

In a normal pregnancy it should be possible to observe the yolk sac between 5-12 weeks of pregnancy or when it reaches 10 mm in size. Abnormal morphological appearance of the yolk sac and/or a size over 9 mm is suggestive of serious growth disorders of the fetus (2).

Is it normal for a gestational sac to be irregular?

Gestational sacs can vary in shape to a certain degree, but an irregular gestational sac is usually a cause for concern as they are predictors of poor pregnancy outcomes. Ultrasounds that show irregular gestational sacs are normally followed up by further ultrasounds or other imaging to confirm the diagnosis and determine the risk of miscarriage.

When will the gestational sac be visible on a transvaginal ultrasound?

The gestational sac forms around five to seven weeks after the last menstrual period in natural cycles, so it is usually visible between 3 and 5 weeks gestational age using a transvaginal ultrasound.

What does the gestational sac look like at 5 weeks?

The yolk sac is surrounded by a larger black area, known as the gestational sac. The gestational sac contains amniotic fluid and surrounds the embryo. You may see the gestational sac in an ultrasound as early as 4 1/2 to 5 weeks.

When does the yolk sac become visible on an ultrasound?

In some cases, a gestational sac will be detected on ultrasound, but a yolk sac is subsequently not found. The yolk sac usually becomes visible on a transvaginal ultrasound between 5 1/2 and 6 weeks gestation.