Ultrasound: Pelvic

OB

In a normal pregnancy, the gestational sac appears as a hypoechoic structure encircled by an echogenic border within the endometrial cavity at 4-5 weeks

IUP at 6 wks

Definite IUP = gestational sac containing yolk sac

• Occurs ~5.5th week
  • MUST contain yolk sac to be confirmed IUP. Pseudogestational sac possible in ectopic pregnancy
• B-HCG below Discriminatory Zone = <1,500-3,000 mIU/ml
• Consider Transabd US for IUP: >6000 mIU/ml

Endometrial mantle

• normal size > 8 mm

Estimated gestational age

• can be measured by crown rump length, femur length, biparietal diameter, etc.
  • depends on gestational age and quality/type of image acquired

Fetal Heart Rate

• normal 120-160
• Use M-mode to calculate
• First visible on US ~6 wks at 100-120 bmp

Nonpregnant

• Ovarian Torsion
  • increased risk with cyst(s) > 5mm
  • Want to visualize arterial and venous flow

Diagnostic Algorithm

See Ectopic Pregnancy

See Also

• Ultrasound (Main)
• Ectopic Pregnancy

Source

• Sonoguide
• Barnhart KT. Ectopic Pregnancy [clinical practice]. N Engl J Med. 2009;361(4):379-387.