Ultrasound: Pelvic

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OB

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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 Transabdominal 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[1]

Nonpregnant

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

Diagnostic Algorithm

See Ectopic Pregnancy

Video

See Also

References

  1. Shetty A, Weerakkody Y. Fetal Heart Rate. http://radiopaedia.org/articles/fetal-heart-rate