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Obstetric Ultrasound Scanning Technique

Obstetric Ultrasound Scanning Technique. Harry Gee (teaching materials provided by David Cole, Lecturer at City University, Birmingham). 2 nd & 3 rd Trimester Scans. Identify fetus Orientation Fetal heart beat Placental site Biometry Bi-Parietal Diameter (BPD)

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Obstetric Ultrasound Scanning Technique

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  1. Obstetric Ultrasound Scanning Technique Harry Gee (teaching materials provided by David Cole, Lecturer at City University, Birmingham)

  2. 2nd & 3rd Trimester Scans Identify fetus Orientation Fetal heart beat Placental site Biometry Bi-Parietal Diameter (BPD) Head Circumference (HC) Abdominal Circumference (AC), Femur length (FL) Liquor Estimation

  3. 2nd & 3rd Trimester Scans • Place probe longitudinal on lower abdomen superior to symphysis pubis • Slide probe superiorly using sweeping movements to locate fetus

  4. 2nd & 3rd Trimester Scans Slide probe superiorly - sweeping side to side up to uterine fundus.

  5. FH + Orientation

  6. Fetal Orientation • Lie • longitudinal • Transverse • Oblique • Presentation • cephalic • breech

  7. Cephalic

  8. Breech

  9. Breech legs extended

  10. Transverse lie

  11. Placental localisation • Full bladder • Midline sagittal section • Placental position anterior or posterior • Low placenta - measure distance between lower edge and internal os *

  12. Fundal placenta

  13. Major placenta praevia

  14. Minor placenta praevia

  15. Liquor volume • Subjective assessment • Maximum deepest pool (MPD) • Amniotic fluid index

  16. Subjective Assessment Normal liquor volume

  17. Maximum deepest pool Deepest pool in cm Do not include cord or fetal limbs

  18. Amniotic Fluid Index Sum of the deepest pools in each of four quadrants

  19. Oligohydramnios MPD < 3 cm up to 36 weeks MPD < 2 cm 36 weeks - term

  20. Polyhydramnios MPD > 8 cm

  21. Fetal Biometry • Biparietal diameter BPD • Head circumference HC • Abdominal circumference AC • Femur length FL

  22. BPD Measurement ROCK

  23. Biparietal diameter BPD

  24. BPD Errors • Few (best inter-observer error) • Oblique section (increases measurement) • Not at BPD (decreases measurement)

  25. Head CircumferenceTrans-ventricular Plane choroid plexus anterior horn posterior horn CSP falx cerebri

  26. Trans-ventricular Plane

  27. Measurement CriteriaBPD & HC • Landmarks: CSP, Falx, thalami • Alignment: symmetrical –midline no orbits, no cerebellum • Calipers: BPD widest distance 90o midline. • HC bony perimeter of skull

  28. Abdominal Circumference • Long Axis of fetus (Spine) • Fetal trunk parallel to transducer • Rotate transducer at right angles • Move up and down until landmarks identified. • Repeat to consistency

  29. Abdominal Circumference spine Ao UV stomach

  30. Abdominal Circumference

  31. AC Sources of Error • Oblique Section (Salami Effect) • Too high • Too low • Abdominal compression (oligo-hydramnios) • Fetal Breathing

  32. FL Measurement • Identify femur close to fetal bladder/pelvis.

  33. FL Measurement • Slide probe so that femur is central

  34. FL Measurement • Rotate probe to obtain full length image of femur.

  35. Femur Length

  36. Source of Error • Oblique image (shortens measurement)

  37. The End

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