THE NORMAL GESTATIONAL SAC     

 

ULTRASOUND

 

 

 

Small gestational sac prior to visualization of the yolk sac or embryo.

Note the marked vascularity on power Doppler at the site of implantation.

 

 

TRUE GESTATIONAL SAC

 

 

 

 

Video clip of an elongated gestational sac in a non-viable pregnancy.

 

 

 

Low implantation of gestational sac in lower uterine segment

 

 

Case 1 (above) – 5 weeks of gestation

 

Case 2  (left) – 8 weeks of gestation

 

 

 

   Intradecidual sign”. This differentiates a low lying pregnancy or cervical ectopic pregnancy from an abortion in progress.

   This sign is only reliable prior to 12 weeks GA as the inferior portion of the gestational sac reaches the uterine corpus by 12 weeks GA.

 

Positive intradecidual sign

  1. It is a sign of a true intrauterine pregnancy.
  2. It differentiates a true gestational sac from a pseudosac (associated with ectopic pregnancy).
  3. It differentiates a low lying pregnancy or cervical pregnancy from an abortion in progress.
  4. An intact gestational sac can be seen in cervical pregnancy, low lying pregnancy and passing abortion.

 

 

Negative intradecidual sign

Conceptus and fluid is in the endometrial cavity and not within the decidua (passing abortion).

Other signs associated with  a negative intradecidual sign include:

1.      Hourglass shape of the uterus due to enlargement of the cervix

(80% cervical pregnancy and 25% passing abortion).

2.      Enlarged corpus only in passing abortion (25%) but not in cervical pregnancy (in passing abortion the pregnancy was initially in the uterine corpus whereas in cervical pregnancy, the pregnancy was in the cervix from the beginning.

3.      External os is more frequently closed in passing abortion (80%) than in cervical pregnancy (60%).

4.      Internal os is more frequently open in passing abortion (38%) than in cervical pregnancy (20%).