1. Obstetric Ultrasound Felipe Moretti, MD Griff Jones, MD, FRCS
Assistant Professor – Uottawa
Maternal Fetal Medicine Division

2. “About 4% of all pregnancies are complicated by one or more major fetal malformations, 2% by a fetal genetic disorder, 1% by miscarriage after the first trimester, and another 1% result in infant death in the first year of life”.
Obstetrical and Gynecological Survey, 2008.

3. What is Prenatal Diagnosis?
Aneuploidy Downs’ Syndrome
Anomalies Spina bifida / NTD
Fetal disease Iso-immunisation (Rh)
Infection
Cardiac arrythmias

4. Obstetric Ultrasound First Trimester scan Second trimester
Third trimester

5. Obstetric Ultrasound First Trimester scan Determine Gestational age
Viability
Number of embryos or fetus
Intrauterine pregnancy

6. First Trimester scan
Determine Gestational age: CRL (Crump Rump Length)

7. Normal Early Pregnancy
Empty uterus
Positive HCG
Gestation sac
Plus or minus yolk sac
Gestation Sac
Fetal pole
No fetal cardiac activity seen
What you see depends when you look, pregnancies can also develop to a point and then fail
Fetal cardiac activity present

8. Viability

9. Viability

10. First Trimester scan
Number of embryos or fetus

11. Intrauterine pregnancy or Ectopic pregnancy

12. First Trimester scan IPS ( Integrated Prenatal Screen):
Combine test with Maternal blood work and Ultrasound
Blood work and US at days: pregnancy associate plasma protein-A (PAAP-A) and free-hCG plus NT
Blood work at weeks: AFP, estriol and inhibin.

13. Fetal Structural Anomalies
Anatomy review done at weeks
Striking a balance
Adequate visualisation of fetal structures
Allow adequate time for further investigation
Leave parents the option of not continuing the pregnancy
Studies have shown a higher detection rate at 20+ weeks

14. Nuchal Translucencia

15. NT

16. IPS result

17. Second trimester Morphology scan at 18-20 weeks
Body System
Detection Rates
Abdominal Wall
95%
CNS
80%
Renal
60%
Skeletal
30%
Cardiac
20% to 50%

18. Difficulties in Imaging
Covered this in gynae talk, after 12 weeks, most of fetus is in the abdomen and therefore can only use low frequency TA probes. Distance to fetus impairs image quality
Obesity

19. Fetal Position Apposing structures Shadowing Orientation Engagement
TV scanning
Heart
Head
Engagement
Spine lying against uterine wall in top image

20. Amniotic Fluid Volume
Fluid surrounding fetus provides contrast, severe oligohydramnios impairs image quality, leads to fetus curling up and makes it less likely fetus with move into a better position

21. Congenital Cardiac Anomalies
Detection rate remains poor
25-50%
Technically difficult
Complex anatomy
Movement
Function changes at birth

22. Small & Rapidly Moving Target

23. Level 2 Ultrasound for Maternal Valproate Exposure
“Normal” genetic sonogram
“Normal” extended anatomy review
Baby discovered to have Downs’ Syndrome at birth

24. Prenatal ultrasound is not a perfect science
Risks are modified
Nothing is 100%

25. Normal Fetal Spine

26. What is wrong with this spine?
Next slide highlights abnormal area

27. Abnormal Lower Spine

28. What if you can’t see the spine?

29. Other ways to make the diagnosis
Banana sign and obliterated cysterna magna, diagnostic especially if AFP elevated
Other ways to make the diagnosis

30. Ventriculomegaly

32. What else Ultrasound can help us in the 2nd and 3rd trimester?
Placenta Location;
Anterior/Posterior/Fundal/Lateral
Previa or non-previa
Presentation;
Cephalic
Breech
Transverse

33. How is the Baby Doing? Fetal Well Being

34. Fetal Growth
There is a higher morbidity and mortality in babies that are small for gestational age
Unfortunately, most babies weighing <10th centile are “normally” grown and a significant number of IUGR babies have birthweights >10th centile

35. Fetal Measurement 2nd and 3rd trimester
Fetal Head: BPD and HC
Fetal Abdomen: AC
Femur Length
Estimate Fetal Weigth (EFW)

36. EFW: 10 to 90% centile

37. Variability in Weight Estimates
Technical / image quality
Caliper placement
Numerous mathematical models
Log weight = (BPD *AC – *AC*BPD)
All tend to be poor at weight extremes
Aim for +/- 10% in 90% estimates
Highlight the mathematical model used to estimate the fetal weight

38. Ultrasound Assessment of Fetal Behaviour
Significant Canadian contribution to the field
Followed on from the introduction of real-time ultrasound
Led to the development of the Biophysical Profile (BPP)

39. Fetal Breathing Occurs 30% of time at term
Clusters lasting 20+ minutes every minutes
Apnea episodes lasting up to 2 hours occasionally seen
Cine clip of breathing, click to start if not automatic

40. Fetal Movement Fetus moves 10% of time at term Average of 31
movements per hour
No movement occasionally occurs
for up to 75 minutes
Cine clip of movement, click to start if not automatic

41. Fetal Tone One episode of extension and return to flexion in 30 min
More recent modification to reflect fine motor activity
Hand opening / closing
Mouth opening / closing

42. Biophysical Profile Component Criteria to score “2”
1.Breathing movements
At least one episode continuing more than 30 seconds. Hiccoughs / hiccups count.
2.Body Movements
At least three body or limb movements.
3. Tone
An episode of active extension with return to flexion or opening and closing.
4. Amniotic fluid volume
At least one cord and limb free fluid pocket which is 2 cm by 2 cm in two measurements at right angles.
Modified BPP without NST

43. Oligohydramnios Three pathologies to consider Renal tract anomaly
Rupture of membranes –
especially if very preterm
Renal hypoperfusion
Compensatory mechanism to maintain blood flow to heart and brain
Analagous to oliguria in sick adults
Seen in IUGR

44. Oligohydramnios and Perinatal Mortality

45. Amniotic Fluid Assessment
One measure
2 x 2 pocket
Single deepest pool
Four quadrants
AFI
Subjective impression
Mention none better at predicting morbidity or mortality but single pocket leads to less unnecessay intervention

46. Doppler

47. Umbilical Artery Doppler

48. Abnormal Umbilical Artery Dopplers
Absent EDF
4x PNM
Reversed EDF
11x PNM

49. Antepartum Haemorrhage
Abruption
By the time an abruption can be seen on ultrasound, there will often be haemodynamic effects on mother or fetus
Praevia
TV ultrasound is diagnostic method of choice

50. Discuss gestational age related changes
The principle role of ultrasound in antepartum haemorrhage is to exclude placenta praevia

51. Classification of Placenta Previa

52. Invasive Diagnostic Tests
CVS 10 to 14 weeks
(earlier result)
Amniocentesis 15+ weeks
Cordocentesis 18+ weeks
(quicker result)

53. Amniocentesis Risk of miscarriage 1 in 400 Done at 15+ weeks
1% chance of amniotic fluid leakage post-procedure

54. CVS Essentially is a placental biopsy Larger diameter needle
More uncomfortable
Higher miscarriage rate (1%)
Technically more challenging
Can be done after 10 weeks

55. Thank You