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2nd trimester scan


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2nd trimester scan

  1. 1. 2nd trimester scanning
  2. 2. 2nd trimester scanning Confirming dating of pregnancy Fetal normality/ abnormality Placental localisation AF volume
  3. 3. BPD Correct levels 2 views: lateral ventricle view, thalamic view More accurate than CRL +/- 5 days Maximum diameter of transverse section of fetal skull at level ofthe parietal eminences
  4. 4. BPD Lateral ventricle view: Rugby shaped skull Long midline equidistant prox-distal skull echoes Cavum septum pellucidum (CSP) bisecting midline Two anterior horns of lat ventricle- symmetrical Post horns of lat ventricle- symmetrical
  5. 5. BPD Lateral ventricle view
  6. 6. BPD Thalamic view: Rugby ball shape Short midline CSP The thalami (arrow head)
  7. 7. Thalamic view BPD
  8. 8. BPD Both levels comparable HC/OFD same level Outer to outer Outer to inner OA/OP position
  9. 9. BPD To obtain the correct level
  10. 10. BPD Estimating GA from BPD: Not to rely on estimates of GA from US software GA should not be made from single parameter Different charts GA and growth require different charts and charting
  11. 11. BPD Estimating GA from BPD
  12. 12. BPD Confirming or assigning GA: If LMP and earlier dating 1st trimester US matches- stick to this date 2nd trimester US is only for growth and not for dating If the 2nd trimester US is the first scan done error is greater: below 24w +/- 2 w After24w >3w
  13. 13. Head circumference Same view as BPD Outer to outer Superior to BPD for dating
  14. 14. Abdominal circumference Landmark features: Circular section with ribs One vertebra -triangle of 3 white spots Umbilical vein (short) - hockey stick Stomach left abdomen Good for dating of pregnancy Sensitive to growth aberrations Fetal weight assessment
  15. 15. Abdominal circumference
  16. 16. Femur length As accurate as BPD for GA From 12w to term Slide probe caudally from AC section till iliac bones Cross section of 1 femur seen Upper femur for measurement Rotate
  17. 17. Femur length
  18. 18. Femur length
  19. 19. Placental localisation Placenta is more echogenic than myometrium Alignment of probe standardised Cervix to the right Fundus to the left
  20. 20. Placental localisation
  21. 21. Placental localisation Cervical canal directly posterior to bladder Lower edge >5 cm from internal os <5cm low lying Placentae previa after 28w Braxton hicks
  22. 22. Placental localisation
  23. 23. Placental localisation Localisation at 20-22w 5% low lying Only 1% placenta previa
  24. 24. Placental localisation
  25. 25. Amniotic fluid volume Produced by fetal kidneys (urine) and removed by fetal bowel (swallowing) Oligohydromnios = decreased volume Polyhydromnios = increased volume Measurements : Visual Max vertical depth 3cm AFI - <5cm =oligo, >25cm = poly
  26. 26. Fetal anatomy assessment Dependant on sonographer- correct images, correct interpretation Go through all-complete coverage--> then no major abnormalities will be missed E.g.After 12w - anencephaly
  27. 27. Fetal anatomy assessment
  28. 28. Fetal anatomy assessment After 20-22w: encephalocoele cystic hygroma abdominal wall defect lemon sign - spina bifida banana sign - hydrocephalus severe limb reduction ascites pleural effusion severe oligo/ polyhydramnios
  29. 29. Fetal anatomy assessment
  30. 30. Fetal anatomy assessment Cerebral ventricles
  31. 31. Fetal anatomy assessment Anterior horn
  32. 32. Fetal anatomy assessment Posterior horn
  33. 33. Fetal anatomy assessment AVHR/PVHR: < 0.5 after 18w gestation Ventriculomegaly
  34. 34. Fetal anatomy assessment
  35. 35. Fetal anatomy assessment
  36. 36. Fetal anatomy assessment Fetal heart: Occupy 1/3 with apex pointing to the left 3 views of the heart: 4 chamber view 2 outflow tract views
  37. 37. Fetal anatomy assessment Fetal heart: moderator band = right ventricle 2 ventricles/ walls of equal size 2 atria / walls of equal size apex point left of fetal chest foramen ovale moving in left atrium pulmonary veins entering left atrium motion of mitral valves (left side) regular motion of tricuspid valves (right side) regular 'offset crux' of the heart: AV valve should not insert into IV septum at the same level intervertebral septum should be complete
  38. 38. Fetal anatomy assessment
  39. 39. Fetal anatomy assessment Fetal heart: Abnormalities of 4c view: No disparity in size between 2 ventricles Tricuspid/ mitral valve defects: Enlargement of atrium Hypoplasia of ventricle
  40. 40. Fetal anatomy assessment eg: (i) regurgitation of tricuspid valve - enlarged right atrium (ii) hypoplastic left heart syndrome - left ventricle small (iii) coarctation - right ventricle enlarged (iv) Ebstein anomaly - enlarged right atrium due to abnormal implantation of tricuspid valve normal IV septum - excludes VSD normal offset crux - exclude AVSD Both ASD & AVSD are assessed with trisomy 21
  41. 41. Fetal anatomy assessment Fetal heart: The aortic outflow tract rotate to right fetal shoulder
  42. 42. Fetal anatomy assessment Demonstrate left ventricle: continuity of IV septum--> ant wall of aorta--> aortic valve & short section of ascending aorta Abnormal AOT: Overriding aorta Aortic stenosis Double outlet right ventricle Fallot's tetralogy
  43. 43. Fetal anatomy assessment Pulmonary artery outflow tract: Demonstrate: Right ventricle Pulmonary valve Main pulmonary artery abnormal in double outlet right ventricle & pulmonary stenosis
  44. 44. Fetal anatomy assessment Fetal abdomen: Single left sided stomach bubble--> after 16w Cord insertion Abdominal defects --> oomphalocoele, gastrochisis Kidneys
  45. 45. Fetal anatomy assessment Cleft lip and palate: Incidence 1:700 births 80% isolated incidence But association with trisomy 13 &18, anti epileptics drugs
  46. 46. Fetal anatomy assessment Fetal sex: Recognisable from 14 weeks
  47. 47. Craniospinal abnormality Causes of increased AFP
  48. 48. Craniospinal abnormality
  49. 49. Craniospinal abnormality
  50. 50. Craniospinal abnormality
  51. 51. Craniospinal abnormality
  52. 52. Craniospinal abnormality
  53. 53. Craniospinal abnormality Between 16-24w --> only as a marker
  54. 54. Craniospinal abnormality Hydrocephalus
  55. 55. Craniospinal abnormality Encephalocoele
  56. 56. Craniospinal abnormality Hydrancephaly Porencephalic cysts
  57. 57. Craniospinal abnormality Dandy walker malformation
  58. 58. Chest abnormality Diaphragmatic hernia
  59. 59. Fetal abdominal abnormality Double bubbleduodenal atresia
  60. 60. Fetal abdominal abnormality Double bubbleoesophageal atresia
  61. 61. Fetal abdominal abnormality Dilated bowels
  62. 62. Fetal abdominal abnormality Oomphalocoele
  63. 63. Fetal abdominal abnormality Gastrochisis
  64. 64. Fetal abdominal abnormality Renal agenesis Cystic disease of the kidneys
  65. 65. Fetal abdominal abnormality Fetal hydrops