Fetal Biometry

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 genome aneuploidy external influences infection drugs Stage being set for later effects smoking maternal nutrition uterine circulation

Environment (diff. populations and over time) Fetal Growth 2nd – 3rd trimesters Why 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

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)

Measurement of BPD

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)

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

Measurement of AC

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

Measurement of FL

Summary of fetal growth prediction 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

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

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

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

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

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

Placental Localisation Identify placenta previa Major previa Minor previa Identify succenturiate lobes Identify vasa previa

TA- Sagittal midline suprapubic image

Posterior Placenta Praevia

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

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

Cervical length at 18 weeks and risk of preterm delivery  32 weeks 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.

Bulging membranes