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Fetal Biometry

Fetal Biometry. Embryonic/fetal growth 1 st trimester. Crown rump length best index of gestational length Phase of most rapid growth in length (up to first ½ preg.) Time when growth influenced most by genome aneuploidy external influences infection drugs

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Fetal Biometry

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  1. Fetal Biometry

  2. Embryonic/fetal growth 1st trimester • Crown rump length best index of gestational length • Phase of most rapid growth in length (up to first ½ preg.) • Time when growth influenced most by genomeaneuploidy external influences infection drugs Stage being set for later effects smoking maternal nutrition uterine circulation

  3. Fetal Growth 2nd – 3rd trimestersWhy has it happened what will be the best tests? • Environment (diff. populations and over time) maternal factor small maternal size (customise) smoking-dose dependent (200g) parity preeclampsia previous FGR glucose concentrations

  4. Measurement of BPD • Short midline, 90 degrees to the beam • Oval shape • Thalami • NO cerebellum or orbits • Cavum septum pellucidi • Measure from outer bone to inner bone at widest point (parietal eminence)

  5. Measurement of BPD

  6. Measurement of HC • Short midline, 90 degrees to the beam • Oval shape • Thalami • NO cerebellum or orbits • Cavum septum pellucidi • Measure circumference of outer bone (usual to put calipers at occiput then sinciput)

  7. Measurement of AC • Transverse section through abdomen • As round as possible • Transverse spine and short length 1 rib • Stomach • Short length umbilical vein and right portal vein approximatly 1/3 from anterior abdominal wall • NO kidney, bladder, heart. Adrenal allowed

  8. Measurement of AC

  9. Measurement of FL • Full length femur • Bone 90 degrees to the beam • Both ends clearly seen • Skin line separate and beyond bone end • Measure from bottom of ‘U’ either end • Bring in calipers from wider point to end

  10. Measurement of FL

  11. Summary of fetal growthprediction of IUGR • Poor predicitors of IUGR Single estimates of fetal size AFV Umbilical artery resistance (doppler) • Useful fetal abdominal area (AC) fetal growth velocities • Owen et al BJOG 2003; 411-415

  12. www.gestation.net l.mccowan@auckland.ac.nz

  13. Placental Failure Reduced utero/plac blood flow Small surface area Altered Maternal Substrate Hypoglycaemia Hypoxia Preeclampsia FGR APS,uterine abns,plac infarct Malnutrition Altitude, anaemia,cyanosis Pathophysiological factors and clinical conditions

  14. Reduced fetal drive Chromosomal anomalies Gene defects Endocrine disorders Fetal anomalies Extnal/int.growth inhibition Drugs, smoking age, infections Aneuploidy, Chr15 IGF-1r loss PKU Pancreatic,thyroid Renal, cong.heart Cytotoxics,radiation, rubella, CMV, mat age extremes

  15. Twin growth • Discordancy defined as >15% difference • Search for cause of discordancy FGR abnormality TTTS • Controversy over twin growth rates use of singleton charts

  16. 50th birthweight percentiles Alexander et al Clinical Obstet Gynecol 41:1;115-125

  17. Placental Localisation • Identify placenta previa • Major previa • Minor previa • Identify succenturiate lobes • Identify vasa previa

  18. TA- Sagittal midline suprapubic image

  19. Posterior Placenta Praevia

  20. Placental Localisation • When to rescan if identified at: • 14 weeks? • 20 weeks? • 32 weeks? • 37 weeks? • Placenta accreta

  21. Cervical length Assessment • TA, TL or TV • Indications • Previous cervical surgery • Previous midtrimester losses (14-24 weeks) • Previous PPROM • Previous PTL • Timing • 14-18 weeks

  22. Cervical length at 18 weeks and risk of preterm delivery  32 weeks Cervical Length(mm) RR(95%CI) PPV 10 29 (11-76) 48% 15 24 (13-46) 41% 20 18 (11-31) 32% 25 13 (8-21) 30 3 (2.4-4) Hassan et al. Am J Obstet Gynecol 2000; 182: 1458-67.

  23. Bulging membranes

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