1. Obstetrical Measurements 2nd & 3rd Trimester
Fetal Biometry Workshop
Day 2 & Day 3

2. Learning Objectives List guidelines for 2nd & 3rd trimester OB exams
Evaluate fetal anatomy
Fetal "screening" may be performed as either part of a basic exam ("level 1") or a detailed scan ("level 2" or higher).  A basic or level 1 scan does not need to make a specific diagnosis but should be able to tell when something is wrong, resulting in a referral for a detailed or "level 2" scan.  Both the "screen" and the "diagnosis" can even take place at the time of a single ultrasound.

3. Protocol – 2nd & 3rd Trimester
Cervix
Fetal Lie
Situs
AFI
Placenta
Cord
Facial Profile
Nose & Lips
BPD & HC
Cerebellum
Cisterna Magna
Choroids
Lateral Ventricle
Diaphragm AC
Bladder
Kidneys
Fetal Heart
4 chamber
LV & RV outflow
3 Vessel view
Femur length
Extremities
Phalanges
Gender
Spine
One of the most important technical considerations in developing scanning expertise is to become organized and systematic in assessing the fetus, placenta, and amniotic fluid

4. Cervix
Avoid measuring the cervix with a LUS contraction or overly distended bladder.
Need fluid in front of the internal cervical os to comment on relationship to placenta

5. Cervix Normal = 3-4cm If >4 bladder is probably too full
Empty and rescan
If < 3cm
Evaluate with translabial first then transvaginal
If evaluating by TV, maternal bladder should be emptied
Watch out for curved cervix make sure you trace the curve instead of straight line
Most of the time cervix is stable from day to day

6. Cervix Preterm labor <37 weeks gestation
Cervical effacement and dilatation
Funneling
Cervix is shortened
The cervix appear to be separating apart

7. Why we need to see cervix…

8. Fetal Lie
These vectors demonstrate the three major possible axes that a fetus may occupy. Fetal lie does not necessarily indicate whether the vertex or the breech is closest to the cervix.
Knowledge of the plane of section across the maternal abdomen (longitudinal or transverse) and the position of the fetal spine and left-side (stomach) and right-side (gallbladder) structures, can be used to determine fetal lie and presenting part.

9. Fetal Lie Cephalic/Vertex Breech Transverse Right side Left Side
Fetal spine toward maternal Right
Stomach towards maternal front
Left Side
Fetal spine toward maternal left
Stomach towards maternal back
Breech
Right Side
Fetal Spine Toward maternal left
Transverse

10. Fetal Lie
A, This transverse scan of the gravid uterus demonstrates the fetal spine on the maternal right with the fetus lying with its right side down (stomach anterior, gallbladder posterior). Because these images are viewed looking up from the patient’s feet, the fetus must be in longitudinal lie and cephalic presentation.
B, When the gravid uterus is scanned transversely and the fetal spine is on the maternal left with the right side down, the fetus is in a longitudinal lie and breech presentation.

11. Fetal Lie
C, When a longitudinal plane of section demonstrates the fetal body to be transected transversely and the fetal spine is nearest the uterine fundus with the fetal left side down, the fetus is in a transverse lie with the fetal head on the maternal left.
D, When a longitudinal plane of section demonstrates the fetal body to be transected transversely and the fetal spine is nearest the lower uterine segment with the fetal left side down, the fetus is in a transverse lie with the fetal head on the maternal right. Although real-time scanning of the gravid uterus quickly allows the observer to determine fetal lie and presenting part, this maneuver of identifying specific right- and left-side structures within the fetal body forces one to determine fetal position accurately and identify normal and pathologic fetal anatomy.

12. Breech Position Complete Frank Footling Baby sits with legs crossed
Bottom first
Legs are up by face
Footling
Either foot comes first

13. Vertex or Breech?

14. Vertex or Breech?

15. Vertex or Breech?

16. Situs Situs Solitus Situs Inversus Heterotaxy or Situs ambiguous
Larger lobe liver on right
Gallbladder on right
Stomach on left
Spleen posterior lateral
Abdominal aorta posterior
IVC anteriorly on right
Situs Inversus
Right / left relationships reversed
Heterotaxy or Situs ambiguous
Complex / hard to define
Jumbled-up arrangement non paired organs
Asplenia or Polysplenia
Heterotaxy = Greek for other arrangement
Arrangement of organs different from the orderly arrangement of either situs solitus or inversus;
Heterotaxy with asplenia = symmetric liver extending from one side of abdomen to the other with stomach on either side
Most cases IVC and Abd Ao are juxtaposed on same side of spine; with Ao in front of IVC
Heterotaxy with polysplenia = liver asymmetric contour with one side being larger than the other; IVC interruption of superrenal-infrahepatic segment & connects to the azygos or hemiaszygos verin t drain into the SVC.
Interruption of IVC – vessels are seen in front of spine in transverse view
Upper abdomen and thorax

17. Amniotic Fluid Aides in symmetrical growth Cushions fetus
Prevents adhesions
Freedom of movement for fetus
Aides in lung, GI, and musculoskeletal development
Maintains constant temp. for fetus
Prevents infection

18. Production of AF 1st Trimester 12 wks to term
Cells lining amnion secrete AF
H2O diffuses across chorion frondosum
Prior to kidney function, passive diffusion from fetus across skin
Amnion covers cord
12 wks to term
12-15 weeks kidneys start to produce amniotic fluid
Fetal kidneys produce majority of fluid through urination
AF increases till about 30 weeks

19. Resorbtion of AF Ingested by fetus
At term rate of ingestion = urine production
Equilibrium must be maintained

20. Composition of AF Early pregnancy is clear or translucent fluid
Later in pregnancy it becomes cloudy
Vernix
Cells from skin and cord
Lanugo (fetal body hair)
Alkaline pH
98% H2O/2% is salts and organics

21. Measuring AF Not measured till 18 wks
Make sure transducer is perpendicular,
No tilting of transducer
Use Color to make sure no cord or baby part in pocket
Cord can be difficult to see especially in 3rd trimester pregnancies
Measure A-P

22. Variety of thresholds for normal:
Cayle – oligohydramnios -- < 7 – 8 cm
Rutherford – oligodhyrominos -- <5
Normal >5 & <18 to 20 cm

24. Placenta

25. Placenta
sonogram in the second trimester demonstrating form of placenta previa. In this case, the inferior placental edge is shown to encroach upon the posterior cervix but not reach or cover the internal cervical os

26. Umbilical Cord 3 vessel cord = 2 arteries + 1 vein
Oxygenated blood through vein
Deoxygenated blood through arteries
Transverse slice through cord, Mickey mouse
Want to see cord insertion site (fetus and placenta)
Can watch the 2 arteries separate around bladder ( no this does not count as a three vessel cord pic)
Umbilical artery fusion may occur
In this case the outcome is not the same as a 2 vessel cord patient
The umbilical cord forms during the first five weeks of gestation (seven menstrual weeks) as a fusion of the omphalomesenteric (yolk stalk) and allantoic ducts.
The cord is surrounded by a connective tissue called Wharton's Jelly.
Excessive whartons jelly can make the umbilical cord appear abnormally thick in a normal pregnancy
Twisted Cord
Due to growth of the vessels and the differential blood flow within the umbilical arteries
Rt umbilical artery is larger than the Lt
Mostly twisted towards Left
Twisting of the cord allows for it to be less resistant to compression
The umbilical arteries originate from the left and right common iliac arteries

27. Umbilical Cord 2-vessel cord – 0.5% to 1.0% of all pregnancies
Due to either primary agenesis of one of embryonic umbilical arteries or atrophy of previously normal umbilical artery
Sonographic – best made at fetal end of cord, cord lost braided appearance
Measures > 4.0 mm in diameter

28. Cord Insertion

29. Facial Profile Are the orbits normally spaced?
Are the nose and nasal bridge clearly imaged?
Is a proboscis or cebocephaly present?
Are any periorbital masses?
Is the upper lip intact?
Is the tongue normal size?
Is the chin abnormally small?
Are the ears normal size and position?
Proboscis – a cylindrical protuberance of the face that in cyclopia or ethmocephaly represents the nose
Cebocephaly – form of holoprosencephaly characterized by common ventricle, hypotelorism and a nose with single nostril

30. Nose & Lips
In a profile plane the contour of the nose, upper and lower lips, and chin is observed.
This is an important view in assessing the presence or absence of the nose, lips, and chin.
 Irregularities in nasal contour may indicate a particular syndrome.
 Tangential cuts, with the transducer angled inferiorly to superiorly through the maxilla, demonstrate the nasal septum, openings of the nostrils, and nares.
 In holoprosencephaly, nasal anomalies range from the presence of a proboscis to a single nostril.
 Evaluation of the nasal triad should assess: 1. nostril symmetry; 2. nasal septum integrity; and 3. continuity of the upper lip to exclude cleft lip and palate.
 The sonographer should not mistake the normal nostrils or frenulum for a cleft.
The maxilla marks the posterior border of the nose and is a landmark in assessing the fetus at risk for pre-maxillary protuberance, as seen in Robert’s syndrome.
Nose/lips are outlined by fluid. Highest frequency possible used. Zoomed in properly. Upper lip is completely demonstrated.

31. Fetal Neural Axis Cerebrum – cerebral hemispheres
2 lateral swellings – grow sideways, forward and backwards until they cover the for and midbrain
Outer cortex of gray matter
Underlying white matter
Discrete masses of gray matter – subserve motor areas of cortex
Paired lateral ventricles – divided into 4 lobes – frontal, parietal, occipital, temporal
Corpus Callosum
Largest projection, tract – fibers that connect 2 cerebral hemispheres
Lie superior to cavum septi pellucidi
Absence = significant neurological effect
Cavum Septi Pellucidi
2 midline spaces bounded superiorly by corpus callosum & inferiorly by fornix
Anterior to foramen of Monro
Do not communicate with rest of ventricular system

32. BPD & HC Thalami are paired CSP Lie on both sides of 3rd ventricle
Sit between frontal horns of the lateral ventricles

33. Ventricles Ventricles
Spaces lying within the brain formed from the canal of the embryonic brain tube
Contain cerebral spinal fluid
Early fetal life most of calvarium is filled with fluid-filled structures
Lateral – one on each side of brain, occupy most of each cerebral hemisphere
Communicate w/ rest of ventricles by interventricular foramen [foramen of Monro]
< 18 weeks choroid-filled ventricles dominate fetal cranium
Anterior horn – frontal
Choroid never extends into the anterior horn
Body – central part – expands posteriorly to become trigone
Trigone – atrium – junction of body with posterior & inferior horns
Posterior horn – occipital
3rd Ventricle = slit like midline structure
lies between thalami [2 collections of gray matter]
Choroid plexus extends from interventricular foramen & runs in midline posteriorly
4th Ventricle = diamond shaped space midline in position, lies in front of cerebellum & behind the pons and upper half of medulla oblongata
Continuous with aqueduct of Sylvius
Aqueduct of Sylvius – connect 3rd & 4th ventricle
Forman of Monro [interventricular foramen – connects lateral & 3rd ventricles
Foramen of Magendie – medial opening drains 4th ventricle into cisterna magna
Foramina of Luschka – lateral 2 foramina that drain 4th ventricle into pontine cistern

35. Ventricles
Ventricles = important indicator of normal CNS & cranial development
Lateral ventricle – measured as an initial point of reference
Area measured = atrium. Normally measures < 1 cm throughout gestation.
Posterior or furthest away ventricle
Where the body of the ventricle merges with posterior and inferior (temporal) horns
10 mm rule
>10 = ventriculomegaly
Measure perpendicular across the thickest portion of the choroid plexus
Larger the ventricle = increase in abnormal outcomes
Male fetus ventricles are larger than female vents
Look for dangling choroid
Should not dangling
Typical abnormal measurement is falx to outer vent
If the ventricle is enlarged most often it decreases throughout the rest of the pregnancy

36. Cerebellum

37. Cerebellum Length will equal to wks of GA Size 2.2 cm = 22 wks
After wks dating is not as good
Butterfly wing shape
Posterior, inferior of head
Measure cisterna Magna in same position
45 degree oblique toward back of head from BPD plane
Scan at level of
Vermis
Midbrain
Cisterna magna

38. Cisterna Magna Fluid filled structure
Lies between the cerebellum and occipital bone
> 10 mm - Relate to Dandy-Walker malformation

39. Cerebellum is measured in its longest dimension
Cerebellum is measured in its longest dimension. This measurement is not required
2. If the CSP is demonstrated in the BPD/HC or posterior fossa image, than a separate image is not necessary.
Be sure that the CSP appears as a anechoic space of fluid interrupting the falx, and not the triple line appearance of the falx flanked by the medial walls of the anterior lateral ventricles (when imaging the columns of the fornix seen slightly inferiorly).
3. The cisterna magna should be imaged from a lateral approach and in a plane which also demonstrates the CSP.
4. The lateral ventricle should be imaged in a true transverse plane from a lateral approach to include the ventricular atrium and occipital horn.
It is measured at the posterior margin of the choroid plexus, perpendicular to the long axis of the ventricle, from its medial to lateral walls.
5. Choroid – prominent early in fetal brain & gradually decrease in relative size with increasing gestational age.

40. Fetal heart views
4 chamber view
5 chamber view
Short axis sweep

41. The aorta and pulmonary artery should appear about equal in size.PA
AAo
Ductus Arteriosis
SVC
DAo

42. Fetal Diaphragm Visualization 3% @ 14 weeks 43% @ 20 weeks

43. Biometry in Abdomen Abdominal circumference At level of umbilical cord
Outer perimeter of abdomen

44. Fetal Bladder & Kidneys
Begin to develop ~ 5th week
Function & produce urine ~ 11 weeks
Visible at 17 to 22 weeks - 3rd trimester easier to image due to perirenal fat
The kidneys initially lie very close together in the pelvis.
Gradually they migrate into the abdomen and become separated from one another. They normally complete this migration by the ninth week of gestation.
In some cases, one of the kidneys may remain in the pelvic cavity, whereas the other migrates into the posterior flank of the abdomen.
On ultrasound, the identification of a pelvic kidney may be seen with adequate bladder dilation and may present in the females as a pelvic mass.
 The arterial vascular supply to the kidneys is supplied by arteries that arise from the aorta.
 Usually these vessels disappear as the kidneys ascend, but some of them may persist to account for the variations one may find in the renal arteries.
 At least 25% of adult kidneys have two to four renal arteries.
 The fetal kidneys are subdivided into lobes that may be separated by grooves.
This lobulation usually diminishes by the end of the fetal period, but in some cases the lobes may still be noticeable by the end of the neonatal period.
In the adolescent and the adult patient, persistence of the fetal lobulation and groove may be seen on ultrasound as an echogenic “triangular” notch along the anterior wall of the right kidney.

45. Spine ~ 16 weeks
Normal neural arch - a closed circle with an intact skin covering
Spina bifida the arch is "U" shaped and there is an associated bulging meningocele (thin-walled cyst) or myelomeningocoele.
Spina bifida - systematic examination of each neural arch from the cervical to the sacral region both transversely and longitudinally.
The extent of the defect and any associated kyphoscoliosis are best assessed in the longitudinal scan.

46. Normal Fetal Limbs

47. Femur Length Shaft fairly straight, symmetric and evenly ossified
Lateral surface straight & Medial curved
Accurate only when the image shows two blunted ends

48. Female Genitalia
Hamburger

49. Male genitalia
Turtle sign
If you think cord put on color Doppler

50. Nuchal Translucency Screening
Amnion
Nicolaides and colleagues, 1992

51. Nuchal translucency, Normal and Trisomy 21
Amnion
Nuchal translucency, Normal and Trisomy 21

52. Nuchal translucency increases with gestational age
Amnion
11-14 weeks
All fetuses
Increases with gestation
Requires high level of accuracy
Requires excellent equipment, well trained sonographers, and ongoing quality control
Narrow window of opportunity: wks
NT Screening: Minuses and Questions
Does not replace second trimester fetal survey
A single measurement
Theoretically easy to perform
Associated with aneuploidy
Associated with other anomalies
Risk increases with NT
Independent of biochemisty
Works for multiple gestations
Early Diagnosis
Median 95th %
11 weeks 1.3mm mm
14 weeks 1.9mm mm
Nuchal translucency increases with gestational age

53. Only valid for weeks
Age Adjusted Ultrasound Risk Assessment (AAURA)

54. BPP Fetal breathing movement
Present [normal] if at least one episode of fetal breathing of at least 60 seconds’ duration within a 30 minute observation period
Fetal movements
Present [normal] if at least 3 discrete episodes of fetal movements within a 30-minute observation period
Fetal tone
Normal if upper and lower extremities in position of full flexion and head flexed on chest; at least one episode of extension of extremities with return to position of flexion or extension of spine with return to position of flexion
Amniotic fluid volume
Normal if fluid evident throughout the uterine cavity; largest pocket of fluid greater than 1 cm in vertical diameter
NST – fetal heart rate reactivity
2 or more heart rate accelerations of at least 15 bpm in amplitude and at least 15 seconds duration associated with fetal movements in a 10 minute period

55. BPP 8 – 10 is considered normal
Parameter
Score 2 [Normal]
Score 0 [Abnormal]
Nonstress test [NST]
Reactive: 2 or more fetal heart rate accelerations of at least 15 bpm in amplitude and at least 15 sec duration in 10 minute within a 40-minutes testing period
Nonreactive: 1 or no fetal heart rate accelerations of at least 15 bpm and 15 sec duration in 10 minute within a 40-min testing period
Fetal breathing movement
The presence of at least one episode of sustained fetal breathing of at least 30 sec duration within a 30-min observation period
The absence of fetal breathing or the absence of an episode of breathing of at least 30 sec duration during a 30 min observation period
Fetal body movements
The presence of at least 3 discrete episodes of fetal movements in a 30-min period. Simultaneous limb and trunk movement counted as a single movement.
2 of less discrete fetal movements in a 30-min observation period
Fetal tone
Upper and lower extremities in position of full flexion and head flexed on chest. At least 1 episode of extension of extremities with return to position of flexion or extension of spine with return to position of flexion
Extremities in position of extension or partial flexion. Spine in position of extension. Fetal movement not followed by return to flexion.
Amniotic fluid volume
AFI > 5.0 cm
AFI < 5.0 cm
Maximum score 10
Minimum score
8 – 10 is considered normal
6 is equivocal – repeat profile in 12 hours
4, 2, 0 – fetal compromise and delivery of fetus should be considered.