Obstetric ultrasound

1. OBSTETRIC ULTRASOUND
TECHNIQUES
FETAL AGE ESTIMATION
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2. 2

3. Sequence
•Introduction to Obstetric Ultrasound
•Technology
•Common Uses
•Types of USG
•Indications of Ultrasound Examination
•Application of Ultrasound in Trimesters
•Fetal Age Estimation
•Conclusion
•Q & A session
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5. Introduction to Obstetric Ultrasound
•Use of ultrasound scans in pregnancy
•Introduced in late 1950s
•Provision of good information about the fetus
and its environment
•Determining early intervention or conservative
management
•Safe, non-invasive, accurate, and cost-effective
investigation in fetus
•Important role in care of pregnant women
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Ultrasound Technology
•Principle of SONAR, used by bats and ships
•Generation of high-frequency sound waves
through a transducer

•Pulsed sound waves penetrate till structures of
different tissues densities is reached
•Reflected energy to the transducer is amplified
and displayed on a screen

•Detection of breathing, cardiac actions and vessel
pulsations through real-time ultrasonography

7. Transducer
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Object

8. Common Uses of Obstetric USG
•Obstetrical ultrasound is a useful clinical test to:
–Establish the presence of a living embryo/fetus
–Estimate the age of the pregnancy
–Diagnose congenital abnormalities of the fetus
–Evaluate the position of the fetus
–Evaluate the position of the placenta
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9. –Determine if there are multiple pregnancies
–Determine the amount of amniotic fluid around the
baby
–Check for opening or shortening of the cervix or
mouth of the womb
–Assess fetal growth
–Assess fetal well-being
–Suspected hydatidiform mole
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Common Uses of Obstetric USG cont

10. –Suspected fetal death
–Suspected uterine abnormality
–UCD localization
–Ovarian follicle development surveillance
–Biophysical profile after 28 weeks of gestation
–Observation of intra-partum events
–Suspected poly- or oligohydramnios
–Suspected abruptio placenta
–Adjunct to external version from breech to vertex
presentation
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Common Uses of Obstetric USG cont

11. Types of Ultrasonography
•Trans Abdominal Ultrasonography (TAS)
•Trans Vaginal Ultrasonography (TVS)
•Doppler Ultrasound
•Tissue Harmonic Imaging (THI)
•Three-dimensional Ultrasound (3-D USG)
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12. Trans Abdominal Ultrasound (TAS)
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•Major technique for imaging in 2
nd
and 3
rd
trimester
•Patient to have full bladder because
–Pushes the uterus out of the pelvis
–Provides an acoustic window
–Displaces pelvic bowel loop superiorly
•Real-time ultrasound equipment includes:
–Sector transducers, when access is limited
–Linear curved array transducers, for less distortion
and greater field of view

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14. Trans Vaginal Ultrasound (TVS)
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•Method of choice for
–Monitoring infertility disorders
–Diagnosis of ectopic pregnancy
–Differentiation of normal and abnormal 1
st

trimester pregnancy
–Diagnosis of congenital anomalies in 2
nd
trimester
•Patient to have empty bladder because
–Uterus will be pushed posteriorly out of the field
of view of the transducer

15. •Specially designed high frequency transducers
•Higher resolution images
•Favorable for obese patients or in early stage of
pregnancy
•Limitations include
–Reduced beam penetration
–More invasive nature of the technique
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Trans Vaginal Ultrasound (TVS) cont

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17. Doppler Ultrasonography
•Most widely employed for detection of:
–Fetal cardiac pulsation
–Pulsation in various fetal blood vessels
•Doppler waveform for useful information about
intra-uterine growth retardation
•Use remains controversial due to increased power
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19. Tissue Harmonic Imaging (THI)
•Processing of lower amplitude, higher frequency
waveforms accompanying fundamental frequency
•Lesser clutter and scatter
•Better visualization of fetal structure
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21. Three-dimensional USG (3-D)
•3-Dimensional “cleaner” image of the scanning
•Transducer captures series of images
•3-D processing done by Computer
•Significant improvement in identifying
–Cleft lips
–Spina bifida
–Polydactyl
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23. Application of Ultrasound in Trimesters
•First Trimester
–Commonly performed at 9-12 weeks
•2nd and 3rd Trimester
–Commonly performed at 18-20 weeks
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24. Obstetric USG in 1
st
Trimester
•Identification of Gestational sac and Embryo
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First trimester fetus and yolk sac

25. •Recording the presence or absence of fetal life
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Obstetric USG in 1
st
Trimester cont
Embryo 4 weeks

26. •Identification and documenting the fetal number
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Two gestational sacs,
each containing a yolk sac
Obstetric USG in 1
st
Trimester cont

27. •Evaluation of Uterus and Adnexal structures
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Obstetric USG in 1
st
Trimester cont
Uterus and cervical plug

28. •Measurement of Nuchal Translucency
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Obstetric USG in 1
st
Trimester cont
Nuchal
Translucency

29. 29Triplet with sub-chorionic bleeding

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Twin pregnancy
28 mm CRL in 10 weeks

32. •Fetal life, number and presentation
•Amount of amniotic fluid
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Obstetric USG in 2
nd
and 3
rd
Trimester

33. •Record Placental localization
•Establishment of fetal age and growth by fetal
biometry including
–Bi-parietal Diameter
–Head Circumference
–Femur Length
–Abdominal Circumference
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Obstetric USG in 2
nd
and 3
rd
Trimester cont

34. •Evaluation of the uterus and adnexal structures
•Evaluation of fetal anatomic structures :
–Cerebellum and Cerebral ventricles
–Spine
–Stomach-bowel, abdominal wall at the area of the
umbilical cord insertion
–Bladder and kidney
–All four Limbs
–Four chamber view of the heart
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Obstetric USG in 2
nd
and 3
rd
Trimester cont

35. 35Fetal Cardiac Structure

36. Fetal Age Estimation
•Assessment of gestational age is fundamental to
obstetric care
•Ultrasound is a reliable method for establishing
the length of pregnancy
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37. Fetal Age Estimation in 1
st
Trimester
•Identification of Gestational sac
–Correlation of MSD and CRL with menstrual age
•Visualizing of Embryo by TVS and TAS
–Estimation of gestational age by crown-rump length
•Nuchal Translucency assessment in 1
st
trimester
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39. •Bi-parietal diameter measurement
–Around 09 weeks until end of pregnancy
•Head Circumference measurement
–Gestational age prediction when abnormal skull shape
–Measured on same plane as Bi-parietal diameter
•Abdominal Circumference measurement
–Measurement similar to head circumference
–Less accurate for establishing gestational age
–Perpendicular plane to the long axis of fetus
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Fetal Age Estimation in 2
nd
& 3
rd
Trimester

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Bi-parietal diameter and head circumference measurements
Fetal Age Estimation in 2
nd
& 3
rd
Trimester

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Bi-parietal Diameter

42. •Femur measurement
–Only long bone measured routinely
–Fetal age assessment when head cannot be utilized
for Bi-parietal diameter
•Multiple Fetal growth parameters
–Single parameter increases variability in predicting
fetal age in 3
rd
trimester
–Variability reduction through parameter combination
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Fetal Age Estimation in 2
nd
& 3
rd
Trimester

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44. Conclusion
•Fetal age estimation is fundamental to obstetric
care
•Ultrasound is a reliable method for establishing
the length of pregnancy and in this way can
improve obstetric care
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Thank You

46. Q & A
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