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

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Presentation on theme: "Obstetric Ultrasound Scanning Technique Harry Gee (teaching materials provided by David Cole, Lecturer at City University, Birmingham)"— Presentation transcript:

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

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

4 2 nd & 3 rd 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 Circumference Trans-ventricular Plane choroid plexus posterior horn falx cerebri CSP anterior horn

26 Trans-ventricular Plane

27 Measurement Criteria BPD & HC Landmarks: CSP, Falx, thalami Alignment: symmetrical –midline no orbits, no cerebellum Calipers: BPD widest distance 90 o 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 UV stomach spine Ao

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


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