Click here for the Early Pregnancy Ultrasound Algorithm

Medical necessity: Confirm intrauterine pregnancy (IUP) and evaluate for signs of ectopic pregnancy.

Structures studied: Uterus and its contents, vesicouterine space, and rectouterine space (Pouch of Douglas).


Begin Transabdominally

1.) Obtain a video clip fanning through the uterus in its entirety in the longitudinal and transverse planes. Assess for uterine lie, presence or absence of free fluid and evidence of an IUP.

If the transabdominal scan is non-diagnostic for an IUP, perform a transvaginal scan. 

1.) Obtain a video clip fanning through the uterus in both the longitudinal and transverse (coronal) planes.

2.) Obtain one static representative image. 

no gestational sac, No intrauterine pregnancy

Gestational sac + yolk sac + surrounded by myometrium* = IUP

Gestational sac but no evidence of yolk sac or fetal pole = no iUP

gestational sac + yolk sac + fetal pole + surrounded by myometrium* = IUP


To be diagnostic for an IUP, the uterus must be scanned in it’s entirety in 2 orthogonal planes showing a minimum of a gestational sac (GS) containing a yolk sac. The sac must be confirmed to be located within the endometrial cavity. This is best determined by demonstrating continuity between the endometrial cavity containing the gestational sac and the endocervical canal.  Assessment for myometrial mantle all around the sac in 2 orthogonal planes must be confirmed. *If the myometrium is <6 mm, this is concern for a corneal/interstitial or ectopic pregnancy.

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