The gestational sac
is the earliest sonographic finding in pregnancy
. The gestational sac appears as an ring surrounding a clear center. The gestational sac is an ultrasonic finding characteristic of early pregnancy.
The gestational sac first appears at about 4 weeks gestational age
, and grows at a rate of about 1 mm a day through the 9th week of pregnancy.
As the pregnancy advances, the next structure to become visible to ultrasound
is the yolk sac
. This is a round, sonolucent structure with a bright rim.
The yolk sac first appears during the fifth week of pregnancy and grows to be no larger than 6 mm. Failure to identify a yolk sac when the gestational sac has grown to 12 mm is also usually indicative of a failed pregnancy.
Absence of yolk sac along with absence of beta HCG denotes a failed pregnancy.
Consult your doctor for further advise and management.