Set-up

Transabdominal

• Probe: Curvilinear
• Mode: Early OB
• Starting Depth: 16 cm

Transvaginal

• • Probe: Endocavitary
• Mode: Early OB
• Starting Depth: 10 cm

Views

• Uterus in transverse and sagittal planes
• IUP within uterus = Gestational sac + yolk sac/fetal pole in the fundus
• Adnexa
• Cul-de-sac

Scanning

• Scan through entire uterus in transverse and sagittal planes
• Identify IUP, measure FHR and gestational age
• Look for presence of free fluid
• Scan through adnexa

Measurements

Transverse Uterus (TA probe)

IUP = fetal pole within GS in fundus

Sagittal Uterus (TA probe)

Transverse Adnexa (TA probe)

Sagittal Uterus (TV probe)

Transverse Uterus (TV probe)

Fetal Heart Rate

Using M-Mode, freeze cursor over beating heart, then measure peak-to-peak of 2 subsequent waves

Gestational Sac Measurement

Crown Rump Length Measurement

Biparietal Diameter Measurement

Measurement from outer to inner edge of calvarium perpendicular to falx cerebri

Femur Length

Ruptured ectopic

Gestational sac outside the fundus with free fluid present

Free fluid

Anechoic with sharp edges; may or may not be pathologic

Subchorionic hemorrhage

Blood located between the uterine wall and the gestational sac

Molar pregnancy 

Usually within the uterus and resemble a cluster of grapes

Ovarian Cyst

Physiologic cysts: <3cm

Functional cysts (e.g. follicular or corpus luteum cysts) > 3cm

Not able to identify a yolk sac or fetal probe

Fix → Switch to endocavitary probe, and increase frequency on your probe

Difficulty identifying ovaries 

Fix → Look lateral to the uterus at the level; typically ovaries have a “chocolate chip appearance” 

Mistaking ectopic for IUP

Fix → IUP must have a fetal pole or yolk sac in the gestational sac within the fundus of the uterus

Failing to perform a bedside US because bHCG is below the discriminatory zone

          Fix → A bedside US should be performed if indicated regardless of the quantitative bHCG

→Even if IUP is identified, be sure of examine the adnexa