Ultrasound course

1. Obstetrics Ultrasound: An
overview From 1St
Trimester to delivery
Dr Rafaie Amin
O&G/MFM Consultant
Sarawak General Hospital

2. Why Scan ?
• Adjunct to
– Clinical history
– Physical Examination
– Other modalities of investigations
Diagnosis
Monitor progression
Monitor treatment

3. Before scanning
• Know what you are
looking for, rather than
hoping to see
something during
scanning
• Know strength and
limitation of your USG
machine
• Know how good is your
skill and your limitation

4. When scanning
• Able to see the image optimally
• Able to interpret/describe the image correctly
• Come out with diagnosis or differential or
conclusion.

5. After scanning
• Know how to write an
appropriate report
• Know how to counsel
patient
• Know what is/are the
appropriate
management.

6. First Trimester Scan
• Confirm pregnancy
• Confirm intrauterine/ rule out ectopic pregnancy
• Confirm viability
• Dating
• Diagnose multiple pregnancy and determine
chorionicity
• Diagnose abnormal pregnancy
• First trimester screening for Trisomy 21
• First trimester structural survey
• Uterine artery doppler

7. Sonographic Detection
• Thickened
endometrium –
decidual changes
• Intra-decidual Sac
Sign (IDDS)
• Yolk Sac
• Amnion
• Embryo
• Fetal heart activity

8. UPT
Negative
Secretary Phase
Early Pregnancy
Complete Miscarriage
Incomplete Miscarriage
Thickened
endometrium

9. UPT
Positive
Early Pregnancy
Completed Miscarriage
Incomplete Miscarriage

13. Double Ring Sign Chorionic
villous
Decidua

17. Amnion-Chorion
Amniotic Cavity
Chorionic Cavity

20. Normal Pregnancy
• Transabdomen
1. Double ring – MSD 10
mm
2. Yolk sac- MSD 20 mm
3. Embryo- MSD 30* mm
4. Fetal Heart- CRL 9mm
• Transvaginal
1. Double ring- MSD
5 mm
2. Yolk sac –MSD 8
mm
3. Embryo – MSD 25**
mm
4. Fetal heart- CRL 7 mm

21. Question answered?
• Is there IUP or ectopic ?
• Is IUP viable ?
• Is date correct ?
• How many GS ?
• If multiple sac, what is chorionicity, amniocity?
• Is there yolk sac?
• Is there a normal embryo?
• Is there any adnexal mass?

22. Combined First Trimester Screening

23. CRL Sagittal plane

25. NT + 1ST Biochemical +++

26. Which one is the best ?
Test DR FFR
A cFTS (Age + NT +BHCG + PAPPA) 85% 5 %
B Second Trimester Quad test ( AFP +BHCG +
Ue3 + Inhibin)
81% 5 %
C Age + NT
Age + NT + (NB + TF +DV)
75%
80% 87%
94%
5%
3%
D First Trimester Serum screening ( BHCG +
PAPPA + AFP +PIGF)
Integrated (1St Trimester BHCG + PAPPA) + (2nd
Trimester Quad test)
90%
90%
20%
2%
E Integrated cFTS + 2nd Quad 95% 5%
BJOG. 2004;111(6):521
N Engl J Med. 2005;353(19):2001.
Prenat Diagn. 2015;35(12):1182. Epub 2015 Sep 7.
.

27. Screening for risk of Pre-Eclampsia

28. DCDA

31. DCDA

32. Biometry
For Accurate Measurement
• Correct Plane
• Image as big as possible
• Correct Placement of the
calliper

33. BPD and HC

34. Biparietal Diameter
• Landmark
– Falx cerebri
– Cavum septum pellucidum
(CSP)
– Thalamus with 3rd ventricle
– Posterior horn of lateral
ventricle
– Sylvian sulcus
• Outer to inner
perpendicular to the
midline.
• Do not include soft tissue
around the bone.

37. Abdominal Circumference
• Landmark
– Stomach shadow
– Spine
– Abdominal part of
umbilical vein
– Left portal vein
• Kidneys and/or rib
should not visible in the
plane

38. Abdominal Circumferences

40. Femur Length (FL)
• Obtain image which is
parallel to the top of
the screen as this gives
the most accurate
measurement of FL
• Taken from the central
end-point of each
metaphysis

42. Mean Sac Diameter
– Usually early, less than 6 weeks
– Should only be used before the
appearance of the embryo
– Use Mean Sac Diameter (MSD).
– Most reliable up to 14 mm MSD
– Generally accepted up to 25mm MSD
– Accuracy +/- 5 days.
– Repeat scan after 10-14 days to
establish viability.
MSD + 35 DAYS = POG in days

43. Crown Rump Length (CRL)
– Once embryo is seen, CRL should be measured.
– Can be used up to 14 weeks (CRL 84 mm).
– Be careful not to include Yolk Sac (YS) in the
measurement.
– Measure pole to pole if fetus not well formed.
– True mid sagittal view in well formed fetus.
– Accuracy +/- 5 days (up t0 9 weeks) +/- 7 days (10-
14 weeks)
– No need repeat scan to confirm date.

44. CRL: Fetal Pole
CRL + 42 DAYS = POG in days

45. CRL: Well formed fetus

46. Not Mid Sagittal

47. • Between 12-14 weeks,
if there is a difficulty in
obtaining true mid
sagittal plane, then a
composite
measurement of FL-BPD
or FL-HC can be used
(accuracy +/- 7 days)

48. 14-24 weeks, FL, BPD, HC
– From 14 weeks onward Femur Length (FL) and
Biparietal Diameter (BPD) or Head Circumference
(HC) should be measured.
– Use composite date based on FL-BPD or FL-HC
– Accuracy +/- 10 days
If there is significant different between femur and head measurement,
consider fetal anomaly (either skeletal or brain anomalies)

49. Deciding Date
– Up to 14 weeks :- Use LMP if USG date is within +/- 5-7
days of LMP date by GS or CRL measurement , otherwise
revise the date following USG measurement
– 12-14 weeks (If using FL-BPD/FL-HC):- Use LMP date if USG
date is within +/- 7 days of LMP date, otherwise revise the
date following USG measurement
– 14-24 weeks:- Used LMP if USG date is within +/- 10 days
of LMP date, otherwise revise the date following USG
measurement.
– Do not change the earlier date.

50. 16-24 weeks
• Cervical Length Surveillance in indicated case.
• Monitoring for MCDA/MCMA twin to detect
severe early onset TTTS
• Early Fetal ECHO in indicated case (14-16
weeks)

51. Mid-trimester Screening scan 18-24
weeks

52. Growth Scan
• Usually in 3rd Trimester ( Early even in 2nd
trimester in MCDA Twin)
• Indication:
– Routine
– Monitoring high risk pregnancy
– Suspected small/large baby (Uterus </> dates)
– Follow up small/big baby.

53. Protocol
• CHECK THE GESTATIONAL AGE WHICH
SHOULD BE ACCURATELY ESTABLISH
• Measure BPD,HC, AC,FL
• Assess amniotic fluid volume
• Presentation, lie , placental location
• CHART AND REVIEW YOUR MEASUREMENT.

54. Clinical Interpretation
• The measurement should be plotted on centile chart.
• AC is the most sensitive predictor of fetal weight.
• If serial growth- Not less than every 2 weeks ( AC
increase about 20 mm in every 2 weeks in average
fetus)
• EFW- Hadlock using combination of BPD,HC,AC,FL
appear to be the most accurate.

55. Symmetrical/Early-onset IUGR

56. Late onset IUGR

57. Macrosomia

58. DOPPLER IN OBSTETRICS
• Doppler ultrasound provides a non-invasive
method for the study of placenta and fetal
hemodynamics.
• Investigation of the uterine and umbilical arteries
gives information on the perfusion of the
uteroplacental and fetoplacental circulations,
respectively,
• Doppler studies of selected fetal organs are
valuable in detecting the hemodynamic
rearrangements that occur in response to fetal
hypoxemia.

59. DOPPLER IN OBSTETRICS
• DOPPLER VELOCIMETRY : Pregnancy
assessment mainly in 3 areas;
1. Maternal site: Uterine artery
2. Placenta site : Umbilical artery
3. Fetal circulation (i.e middle
cerebral)

60. Umbilical artery
doppler

61. TECHNIQUE
• Identify a free-floating loop of cord and try to avoid
sites adjacent to the placenta or fetal abdomen
• Using PW doppler, position the gate over the
umbilical artery.
• Ensure that the doppler angle is acute enough (<60
degree is optimal), otherwise the trace will be small
and inaccurate

62. UMBILICAL ARTERY FLOW
characteristic saw-tooth appearance of arterial flow in
one direction and continuous umbilical venous blood flow
in the other.
Umbilical artery

63. Benefit of Umbilical Artery Evaluation
Less experienced operators can achieve
highly reproducible results with simple,
inexpensive continuous-wave equipment .
Umbilical artery

64. •With advancing
gestation, umbilical
arterial Doppler
waveforms demonstrate a
progressive rise in the
end-diastolic velocity and
a decrease in the
pulsatility index.
Umbilical artery

65. Umbilical artery doppler
• Good in identifying early onset IUGR
• Not reliable in identifying late onset IUGR and
associated complications.
MCA waveform analysis emerge as a promising diagnostic
tool for the diagnosis of late third trimester IUGR among
those with normal UA doppler.
Further studies are required to support its widespread use

66. Middle cerebral artery
doppler

67. An early stage in fetal adaptation to hypoxemia - central
redistribution of blood flow
( brain-sparing reflex)
increased blood flow to protect the brain, heart, and
adrenals
reduced flow to the peripheral and placental circulations
Middle cerebral artery

68. When the fetus is hypoxic, the cerebral arteries
tend to become dilated in order to preserve
the blood flow to the brain and The systolic
to diastolic (A/B) ratio will decrease (due to
an increase in diastolic flow)
Middle Cerebral Artery

69. (the angle q between the beam and the direction of flow
becomes smaller). This is of the utmost importance in
the use of Doppler ultrasound.
Freq.
q
The angle of insonation
Flow velocity
3
2
1
Factors affecting doppler frequency

70. Angle of isonation
• Optimum angle : 0-30 degree

71. (the angle q between the beam and the direction of flow becomes
smaller). This is of the utmost importance in the use of Doppler
ultrasound.
beam (A) is more aligned than (B)
The beam/flow angle at (C) is almost 90° and there is a very poor Doppler signal
The flow at (D) is away from the beam and there is a negative signal.

72. Assessment of liquor volume
• Subjective evaluation
• Maximum volume pocket
(MVP)
• Amniotic fluid index (AFI)

74. Amniotic fluid index
technique
• Identify deepest
unobstructed vertical pool of
liquor
• Calipers to be placed in
vertical position
• Process repeated in four
quadrants
• Sum of values (in cm) = AFI

75. Maximum/Deepest Vertical
Pocket(MVP/DVP)

76. Summary
Weeks/POA Objectives
5-10 Confirm pregnancy
Rule out ectopic
Diagnose twin and its chorionicity
Diagnose abnormal pregnancy
Dating
11-13+6 Dating
First Trimester screening for aneuploidy
Screening for Pre-eclampsia
Early structural survey
Twin chorionicity
14-20 Surveillances for Monochorionic twin ( Start from 16/52)
Cervical length surveillance (16-24/52)
Early fetal Echo in high risk
Dating
20-24 Mid-trimester screening scan
Cervical length screening/continue surveillance
> 24 Growth and liqour
Placenta location
Presentation

77. How frequent do we need to do scan?
• My Ideal for everyone
11-14 weeks
dating
FTS and PE screening
20-24 weeks
Mid-trimester screening
28-34 weeks
Growth
• Minimal standard for
low risk patient in
Sarawak
Dating: < 20 weeks
Growth: 28-36 weeks