This document provides guidelines for performing obstetric ultrasound scans. It outlines the key steps in the scanning process, including getting started, setting gains, performing fetal surveys and anatomical scans, assessing amniotic fluid and placenta location, and writing the report. Details are provided on anatomical landmarks, measurements, and normal structures to evaluate for various gestational ages. The importance of a clear, organized report that addresses the clinical question and provides relevant conclusions is emphasized.

1. Methodological obstetric
scanning
Dr Abdisamad Abdullahi
SHO Radiology
Mbrara university

2. Steps: Should be followed
systematically
1. Getting Started
2. Setting the gains
3. Fetal Survey
4. Fetal anatomical Scan and biometry (Scan the
fetus from Head to Toe)
5. Amniotic fluid assessment
6. Localization of the placenta
7. Assessing Maternal Kidneys
8. Report Writing

3. • Getting started
– Introduces Self, greets patient
– Creates rapport
– Makes patient comfortable
– Ensure Privacy
– Explain procedure to the patient
– Obtain patient Information
– Enter patient's details e.g. Name, LNMP, Gravidity,
Any Complaints, Indication(Reason for scan)

4. • Set Gains- Using the
Liver- This is because
the liver is homogenous
and the largest visceral
organ in the abdomen

5. Early pregnancy (1ST Trimester) Scan
• Note the location of pregnancy/sac (Intra/extra uterine/or
heterotopic)- Look at Cervix
• If no evidence of gestation sac, endometrial thickness and
appearance should be described.
• Number of gestation sacs (Single/multiple). If no fetal pole
identified, mean sac diameter (MSD) or GSD should be taken
• Presence of yolk sac (measure size, evaluate for quality)
• Presence of embryo/fetal node/fetal pole, measure CRL
• Viability – Cardiac activity at B-Mode, M-Mode. Use Colour
Doppler if not certain and seek opinion of colleague/second
eye
• Evaluate for sub-chorionic fluid collections/ heamatomas and
size (2 dimensions)
• Measure Nuchal translucency (<3mm)

6. • Neck - Nuchal skin thickness

7. Early pregnancy (1ST Trimester) Scan
• Uterine and Adnexal masses and their appearance,
patient tenderness and vascularity and relation to
other pelvic organs
• Any ovarian cysts e.g. Corpus luteum cyst.
• Define the amount of free pelvic fluid and state if
either a trace, moderate or large amount and
quantify by measuring a volume where possible.
• Amniotic fluid Assessment
– Gestation sac should not appear tight (Qualitative
assessment)
– MSD – CRL should not be <4mm (Quantitative
assessment)

8. Standard Measurements
correlations in Early Pregnancy
• Gestation sac alone = Possible 5 week
pregnancy
• Gestation sac and yolk sac = 5½ weeks
• CRL 1-6mm = <6 weeks
• CRL 6mm = 6 weeks

9. 1st Trimester Scan: Anatomical pitfalls
1. Rhombencephalon (should not be mistaken for
pathology)
• The embryonic/fetal rhombencephalon is visible with
endovaginal ultrasound at ~8-10 weeks as a
hypoechoic region in the embryonic/fetal head.
• The hypoechoic region represents the developing
rhombencephalon/hindbrain (medulla, pons, and
cerebellum).
2. Physiological anterior abdominal wall herniation
• Physiological Omphalocele that usually occurs
between 6-8 and lasts until 12-13 weeks should not
be mistaken for abnormality.
• Consider follow up ultrasound to exclude

10. Rhombencephalon

11. Physiological Herniation of bowel

12. 2nd & Trimester Scan
Fetal Survey
• Survey the entire abdomen
– Location of Fetus (Intra/extra uterine)- Locating
the cervix.
– Number of feti (Single/multiple)
– Viability- Cardiac activity/General fetal
movements
– Fetal presentation
– Fetal lie & position

13. Intrauterine Pregnancy
• Start by locating the
cervix posterior to the
Urinary bladder
• The fetal parts should
be located superiorly to
the cervix with in the
uterus for an
intrauterine pregnancy

14. Fetal Anatomical Scan
• The fetal anatomical scan is best done in the
2nd trimester, when all organs are well
developed and when the amniotic fluid is still
enough, relative to the fetus to allow good
visualisation.
• Also known as the fetal anomaly scan

15. Fetal Head
• Head- Locate the calvarium, brain
parenchyma, Thalami, ventricles, falx cerebri,
cavum septum pellucidi, Cerebellum, cisterna
magna
• Head biometry- Measure BPD
• Land marks for BPD- Calvarium, falx Cerebri,
Thalami, cavum septum pellucidum
• BPD: Measure from outer to inner table of the
Calvarium, midline

16. Land marks For BPD

17. Spine
Scan in both Long axis and Transverse View

18. 1. Look out for nuchal
cord (Cord around
the neck)

19. Neck: Nuchal Skin Fold
1. Measure Nuchal fold thickness at ~18-22 weeks < 6mm

20. Fetal Heart
• Views – 4-Chamber
Outflow Tracts
Short Axis of Great Vessels
• Document Fetal Heart rate: (M-Mode)
• Normal heart rate is about 120-160 beats per
minute (bpm).
• Bradycardia is <100bpm for more than a few
minutes
• Tachycardia of more than 220bpm

21. 4-Chamber Image of the Heart

22. Chambers of the heart.
• Chest
–4 chambered
heart, apex
pointing to the
left
–Lungs

24. • Fetal Abdomen
– Abdominal wall
– Insertion of umbilical cord to the anterior
abdominal wall- 3 vessel cord
– Stomach
– Urinary bladder
– Renal fossa- Kidneys

25. Normal fetal stomach
• Left-sided; Same side as cardiac apex
• Must document fetal stomach after 14wks
- fills and empties in 30 – 45 minutes
- re-scan in 1 week
• Do not mistake gall bladder or umbilical vein for
stomach.
• Measure Abdominal Circumference(AC). AC in
combination with 2 other biometric measurements
id used to estimate fetal weight

26. Fetal abdomen.
Cord insertion

27. Umbilical Cord
• Note the three Vessel
Umbilical cord in
transverse view

28. Fetal kidneys
• Posterior paravertebral locations
• Best seen in late 2nd trimester and third
trimester when the kidneys are well
developed
• Renal size
- 1/3 diameter & area of abdomen
• Capsule very thin
- Early pregnancy: renal regions
• Cortex > echogenicity than medulla
• Renal pelvis: small amount of fluid

29. Fetal Kidneys
• Transverse
• Sagittal

30. Fetal adrenal glands
• Position: above kidneys
• Hypoechoic outer cortex
• Hyperechoic inner medulla
• Tend to be prominent in fetus & neonate cases
of renal agenesis

31. Fetal adrenal glands
Adrenal glands in supra renal
regions
Adrenal gland in unilateral
renal agenesis

32. Fetal urinary bladder
• Visible by 12 – 13 weeks MA
• Cystic area in fetal pelvis
• Fills & empties every 30 – 45 minutes
• Must be documented

33. Fetal Urinary Bladder

34. Fetal external genitalia
• If a patient would like to know the sex of their
baby and it is evident during the scan, the
Sonographer may pass on this information.
• If the sex is divulged, always explain that this
is not 100% guaranteed
• Medical indications for gender identification
- twins, X-linked disorders, lower urinary
tract obstruction, Turner’s suspect,
• Male: scrotum and penis
• Female: labia- maternal hormonal stimulation

35. Female Male

36. Fetal male genitals

37. Female fetus with labia

38. Fetal scrotum ( 1st picture), don’t mistake for
umbilical cord in second picture

39. Fetal Limbs
• Assess the fetal Limbs (both upper & lower)
– Upper Limb: Humerus, radius, ulna and hand
– Lower limb: Femur, tibia, fibula and Foot
• Biometry –FL ( Compare with BPD, should not
be more than 2 weeks variation)

40. Fetal Limbs (Both Upper & Lower)

41. Tibia and fibula and foot
Plantar aspect of the Fetal foot

42. Femur length
• FL measurements include only the diaphysis of the femur is measured
excluding the spurs at the end of the bone from the measurement.
• Compare FL measurements with other biometric measurements,
shouldn’t vary by more than 2 weeks

43. Amniotic fluid assessment
Clinical assessment is unreliable
Qualitative (at US)
Visual assessment- Used by very
experienced persons
Quantitative: Objective assessment depends on
US
a. Deepest Vertical Pool (DVP)
Single pocket 2 – 8cm
b. Amniotic Fluid Index(AFI) :Four quadrant
method

44. Placenta Location

45. Assess Maternal Kidneys
• Rule out Maternal
Hydronephrosis
• Scan both kidneys
• Normal appearance:
Hypoechoic cortex and
medulla, and a hyperechoic
center representing the sinus.

46. Report writing
• An obstetric ultrasound exam is never
complete with out a written report
• A report is never concluded until it has
reached the referring clinician
• If it is urgent, or crucial or critical, if it is an
emergency, you had better deliver it fast by
any means

47. Basic structure of an ultrasound report
• Identification of subject and exam performed,
date of report
• Indication: Reason for scanning, brief history
• Description of findings
• Conclusion
• Recommendations

48. • Clinicians seek for expert
information when they ask for an
ultrasound, and so they expect a
professionally written,
meaningful, clear, and
professional report!

49. What do clinicians want?
• Standard report formats
• Report should follow a logical order
• Take clinical picture into consideration
• Start with brief clinical info and indication
• More descriptive detail
• Clarity: Use clear language
• Appropriate conclusions tallying with clinical picture
& the description
• Focussed differential diagnosis
• Appropriate recommendations

50. Identification
• Identification of subject, and examination,
date sex, date of referral, number
• These are important for quality management
and audit of reports

51. Indication(Reason for scanning)
• Keep short and pertinent
• Indicates to the clinician that the person
scanning the patient is aware of the problem
and addressing it
• If history is inadequate state this explicitly as
you begin the report
“Histories provided are surprisingly a sensitive
indicator of level of medical care by physicians
as well as medical institutions”

52. Description
• Clear , concise, pertinent
• Whenever possible, describe structures following
anatomical arrangement and systems
• Describe pathology first, multiple abnormalities
addressed in order of importance
• If there is no pathology, then first address
clinicians question
• Describe significant positive and negative findings
• Use present tense for what is seen

53. Description (b)
• Descriptive detail depend on the clinical
circumstances
• Organize observations and group in as may
paragraphs as possible

54. Comparison with earlier data
• The report must show how current
observations relate to past investigation, both
radiological and lab, etc, disease is not just a
shot in time , it is a continuation of a
sequence of invents and this must
incorporated this so as to arrive at a
contextual conclusion

55. Interpretation and conclusion
• This is the last part of the report
• This section weaves together data to come to a
meaningful interpretation and diagnosis
• It must be clear to the reader whether the diagnosis
is definite, possible, suspected or equivocal
• Clinical decision making will hinge on degree of
certainty of the conclusion

56. Conclusion (a)
• The degree of certainty must be explicit
• If is equivocal, it leaves the clinician at sea or
in the dark and will prevent evidence-based
management

57. Conclusion (b)
“The statement made in the conclusion are an
excellent gauge of the knowledge, common
sense and clinical judgment of the
sonographer”
They give a good source of assessing the
probability of the disease and the sensitivity
and specificity of the imaging test used

58. Conclusion (c)
• The radiologist should write a phrase in the
conclusion which indicates as to whether the
findings explain the clinical observations or
they don’t.
• At times the conclusions are incidental and
may have no bearing to the symptoms or
possible disease outcome

59. Our currency
“Words really do have a meaning and
importance and are the currency in which we
deal, we should try to be clear, precise and
thrifty”

60. Tautological phrases
• Are a group of words which don’t add any
extra meaning but are at times a duplication
of each other
• These should be avoided
• Example; oval in shape, close proximity, small
in size, slightly anechoic, interval change,
previous history

61. Use of proper sentences
• Sentences must be proper English sentences
with articles, nouns verbs etc
• Not too long with over use of joining words or
the meanings get mixed up
• One observation should be dealt with in a
sentence, multiple observations make the
sentence confusing. Preferably short
sentences.

62. Paragraphs
• Use as many as possible to show you are
orderly and systematic
• Every paragraph should deal with one
particular item or related set of items. Don’t
mix items in a paragraph
• The sentence which begins a paragraph
should be a summary of what is to follow in
that paragraph

63. Summary
A good report must be :
• Appropriately structured
• Unambiguous and precise
• Succinct and direct
• Accurate
• Objective
• Written in the present tense
• The report is a medical consultation and not just a
statement for the rerecords
• It has to reach the clinician fast

64. Don’t forget
• A report is never concluded until it has
reached the referring clinician
• If it is urgent, or crucial or critical, if it is an
emergency, you had better deliver it fast by
any means