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Similar to 2nd trimester scan
2nd trimester scan
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- 2. 2nd trimester scanning Confirmingdating of pregnancy Fetal normality/ abnormality Placental localisation AF volume
- 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. BPD Lateral ventricle view: Rugbyshaped 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
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- 6. BPD Thalamic view: Rugby ballshape Short midline CSP The thalami (arrow head)
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- 8. BPD Both levels comparable HC/OFDsame level Outer to outer Outer to inner OA/OP position
- 9. BPD To obtain thecorrect level
- 10. BPD Estimating GA fromBPD: 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
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- 12. BPD Confirming or assigningGA: 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. Head circumference Same viewas BPD Outer to outer Superior to BPD for dating
- 16. Abdominal circumference Landmark features: Circularsection 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
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- 19. Femur length As accurateas 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
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- 23. Placental localisation Placenta ismore echogenic than myometrium Alignment of probe standardised Cervix to the right Fundus to the left
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- 25. Placental localisation Cervical canaldirectly posterior to bladder Lower edge >5 cm from internal os <5cm low lying Placentae previa after 28w Braxton hicks
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- 27. Placental localisation Localisation at20-22w 5% low lying Only 1% placenta previa
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- 29. Amniotic fluid volume Producedby 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
- 30. Fetal anatomy assessment Dependant onsonographer- correct images, correct interpretation Go through all-complete coverage--> then no major abnormalities will be missed E.g.After 12w - anencephaly
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- 32. Fetal anatomy assessment After 20-22w: encephalocoele cystichygroma abdominal wall defect lemon sign - spina bifida banana sign - hydrocephalus severe limb reduction ascites pleural effusion severe oligo/ polyhydramnios
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- 37. Fetal anatomy assessment AVHR/PVHR: < 0.5after 18w gestation Ventriculomegaly
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- 40. Fetal anatomy assessment Fetal heart: Occupy1/3 with apex pointing to the left 3 views of the heart: 4 chamber view 2 outflow tract views
- 41. Fetal anatomy assessment Fetal heart: moderatorband = 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
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- 43. Fetal anatomy assessment Fetal heart: Abnormalitiesof 4c view: No disparity in size between 2 ventricles Tricuspid/ mitral valve defects: Enlargement of atrium Hypoplasia of ventricle
- 44. 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
- 45. Fetal anatomy assessment Fetal heart: Theaortic outflow tract rotate to right fetal shoulder
- 46. Fetal anatomy assessment Demonstrate leftventricle: 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
- 47. Fetal anatomy assessment Pulmonary arteryoutflow tract: Demonstrate: Right ventricle Pulmonary valve Main pulmonary artery abnormal in double outlet right ventricle & pulmonary stenosis
- 48. Fetal anatomy assessment Fetal abdomen: Singleleft sided stomach bubble--> after 16w Cord insertion Abdominal defects --> oomphalocoele, gastrochisis Kidneys
- 52. Fetal anatomy assessment Cleft lipand palate: Incidence 1:700 births 80% isolated incidence But association with trisomy 13 &18, anti epileptics drugs
- 53. Fetal anatomy assessment Fetal sex: Recognisablefrom 14 weeks
- 55. Craniospinal abnormality Causes ofincreased AFP
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- 61. Craniospinal abnormality Between 16-24w--> only as a marker
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- 67. Fetal abdominal abnormality Doublebubbleduodenal atresia
- 68. Fetal abdominal abnormality Doublebubbleoesophageal atresia
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- 72. Fetal abdominal abnormality Renalagenesis Cystic disease of the kidneys
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