ABNORMALITIES IN LOCATION OF THE GESTATIONAL SAC

• Usually located eccentrically near the uterine fundus.

Normal gestational sac in uterine fundus	Low gestational sac

• Can occasionally be seen in the midportion of the uterine body. Implantation at this site may be impossible to distinguish from an abortion in progress.
• Low position of the gestational sac is thought to represent a stage rather than cause of abortion.
  A gestational sac situated completely or partially in the lower uterine segment is seen in 20% of abnormal pregnancies and predicts an abnormal outcome in 94% of cases (1).

REFERENCES

1. Filly RA. Ultrasound evaluation during the first trimester. In: Callen (ed). Ultrasonography in Obstetrics and Gynecology. 3rd edition. 1994. W B Saunders Company. pg 63-85.