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Obstetric Ultrasound Felipe Moretti, MD Griff Jones, MD, FRCS

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Presentation on theme: "Obstetric Ultrasound Felipe Moretti, MD Griff Jones, MD, FRCS"— Presentation transcript:

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

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