Ultrasound features of a normal gestational sac
By 5 weeks of gestational age, the gestational sac is typically visible as a small, round or oval cystic-fluid collection located within the decidua of the thickened and echogenic endometrium along the upper uterine body.
The gestational sac grows at a rate of 1.1 mm/day and is typically visible by a serum beta human chorionic gonadotropin (β-hCG) level of 1000 to 2000 mIU/mL. Definitive diagnosis of a pregnancy can only be made once a gestational sac contains a yolk sac and/or embryo.
If a suspected gestational sac is seen without a yolk sac or embryo, then follow-up US and/or follow-up serial maternal serum β-hCG levels are performed to ensure accurate diagnosis and management of a potentially viable early pregnancy.
