Obstetric ultrasound

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Obstetric ultrasound

  1. 1. OBSTETRIC ULTRASOUND TECHNIQUES FETAL AGE ESTIMATION 1
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  3. 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 3
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  5. 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 5
  6. 6. 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 6
  7. 7. Transducer Received pulse Transmitted pulse Object
  8. 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 8
  9. 9. Common Uses of Obstetric USG cont – 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 9
  10. 10. Common Uses of Obstetric USG – – – – – – – – – cont 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 10
  11. 11. Types of Ultrasonography • Trans Abdominal Ultrasonography (TAS) • Trans Vaginal Ultrasonography (TVS) • Doppler Ultrasound • Tissue Harmonic Imaging (THI) • Three-dimensional Ultrasound (3-D USG) 11
  12. 12. Trans Abdominal Ultrasound (TAS) • Major technique for imaging in 2nd and 3rd 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 12
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  14. 14. Trans Vaginal Ultrasound (TVS) • Method of choice for – Monitoring infertility disorders – Diagnosis of ectopic pregnancy – Differentiation of normal and abnormal 1st trimester pregnancy – Diagnosis of congenital anomalies in 2nd trimester • Patient to have empty bladder because – Uterus will be pushed posteriorly out of the field of view of the transducer 14
  15. 15. Trans Vaginal Ultrasound (TVS) cont • 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 15
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  17. 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 17
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  19. 19. Tissue Harmonic Imaging (THI) • Processing of lower amplitude, higher frequency waveforms accompanying fundamental frequency • Lesser clutter and scatter • Better visualization of fetal structure 19
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  21. 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 21
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  23. 23. Application of Ultrasound in Trimesters • First Trimester – Commonly performed at 9-12 weeks • 2nd and 3rd Trimester – Commonly performed at 18-20 weeks 23
  24. 24. Obstetric USG in 1st Trimester • Identification of Gestational sac and Embryo First trimester fetus and yolk sac 24
  25. 25. Obstetric USG in 1st Trimester cont • Recording the presence or absence of fetal life Embryo 4 weeks 25
  26. 26. Obstetric USG in 1st Trimester cont • Identification and documenting the fetal number Two gestational sacs, each containing a yolk sac 26
  27. 27. Obstetric USG in 1st Trimester cont • Evaluation of Uterus and Adnexal structures Uterus and cervical plug 27
  28. 28. Obstetric USG in 1st Trimester cont • Measurement of Nuchal Translucency Nuchal Translucency 28
  29. 29. Triplet with sub-chorionic bleeding 29
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  31. 31. Twin pregnancy 28 mm CRL in 10 weeks 31
  32. 32. Obstetric USG in 2nd and 3rd Trimester • Fetal life, number and presentation • Amount of amniotic fluid 32
  33. 33. Obstetric USG in 2nd and 3rd Trimester cont • Record Placental localization • Establishment of fetal age and growth by fetal biometry including – – – – Bi-parietal Diameter Head Circumference Femur Length Abdominal Circumference 33
  34. 34. Obstetric USG in 2nd and 3rd Trimester cont • 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 34
  35. 35. Fetal Cardiac Structure 35
  36. 36. Fetal Age Estimation • Assessment of gestational age is fundamental to obstetric care • Ultrasound is a reliable method for establishing the length of pregnancy 36
  37. 37. Fetal Age Estimation in 1st 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 1st trimester 37
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  39. 39. Fetal Age Estimation in 2nd & 3rd Trimester • 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 39
  40. 40. Fetal Age Estimation in 2nd & 3rd Trimester Bi-parietal diameter and head circumference measurements 40
  41. 41. Bi-parietal Diameter 41
  42. 42. Fetal Age Estimation in 2nd & 3rd Trimester • 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 3rd trimester – Variability reduction through parameter combination 42
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  44. 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 44
  45. 45. Thank You 45
  46. 46. Q&A 46
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