Increased Nuchal Translucency



Increased Nuchal Translucency


Roya Sohaey, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Chromosome Abnormality



    • Trisomy 21


    • Trisomy 18


    • Trisomy 13


    • Turner Syndrome (XO)


  • Congenital Heart Defects



    • Ventricular Septal Defect


    • Hypoplastic Left Heart


    • Atrioventricular Septal Defect


  • Cystic Hygroma



    • Hydrops


  • Normal Amnion (Mimic)


Less Common



  • Nuchal Cord (Mimic)


  • Fetal Demise


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Nuchal translucency (NT) measurement recommended in all 11-14 wk pregnancies


  • Larger NT associated with worst prognosis


  • Look for other first trimester aneuploidy markers at time of NT assessment



    • Absent nasal bone (NB)


    • Ductus venosus (DV) assessment



      • Normal DV with antegrade triphasic flow


      • Abnormal DV with retrograde “A” portion of wave


  • Look for first trimester anomalies



    • Transvaginal ultrasound helpful


  • Correlate NT with first trimester maternal serum results



    • Free β-human chorionic gonadotropin (β-hCG)


    • Pregnancy-associated plasma protein A (PAPP-A)


    • T21 pattern is ↑ β-hCG, ↓ PAPP-A


  • Offer chorionic villus sampling (CVS)


Helpful Clues for Common Diagnoses



  • Trisomy 21



    • Absent NB



      • Absent NB with a crown rump length (CRL) 45-64 mm = 17x ↑ T21 risk


      • Absent NB with a CRL 65-84 mm = 44-48x ↑ T21 risk


      • As NT increases, incidence of absent NB also ↑


    • Abnormal DV waveform



      • Retrograde “A” wave


    • Look for cardiac defect with transvaginal ultrasound



      • Atrioventricular septal defect


    • ↑ NT may evolve into nuchal skin fold thickening in 2nd trimester


  • Trisomy 18



    • T18: Second most common chromosome abnormality


    • Some major anomalies are detectable in first trimester



      • Omphalocele


      • Cardiac defects


      • Musculoskeletal anomalies


  • Trisomy 13



    • T13: Third most common chromosome abnormality


    • Some major anomalies are detectable in first trimester



      • Holoprosencephaly


      • Cardiac defects


      • Omphalocele (omphaloceles containing bowel have higher incidence of chromosomal abnormalities)


  • Turner Syndrome (XO)



    • Largest NTs are seen with TS


    • Cystic hygroma



      • ↑ NT with septations


    • Hydrops



      • ↑ NT + fluid in any one other compartment


      • Pleural effusion


      • Body wall edema


      • Ascites


    • Cardiac defects



      • Hypoplastic left heart


  • Congenital Heart Defects



    • ↑ NT seen with isolated congenital heart defects



      • Normal CVS


      • Normal maternal serum testing


    • Ductus venosus assessment helpful, however not always abnormal


    • Early echocardiography with transvaginal scanning



      • Color Doppler important for small septal defects


    • Second trimester echocardiography



      • If first trimester echo is inconclusive or normal



  • Cystic Hygroma



    • Larger septated mass


    • Increased incidence in Turner syndrome but may occur in chromosomally normal fetuses


    • May develop hydrops



      • Incurs very poor prognosis


  • Normal Amnion (Mimic)



    • Must see both amnion and skin to measure NT



      • Do not confuse amnion for nuchal skin


    • Fetus lies on amnion



      • Obscures the nuchal skin line


      • Wait for fetus to move away from amnion


    • Amnion and chorion normally fuse by 14 wks


Helpful Clues for Less Common Diagnoses



  • Nuchal Cord (Mimic)



    • Umbilical cord behind neck in first trimester



      • Finding is not clinically significant


    • Measuring cord + neck will falsely increases NT


    • Cord can compress skin with focal increased NT


    • Consider bringing patient back on another day


  • Fetal Demise



    • Obvious diagnosis during real time evaluation

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Aug 10, 2016 | Posted by in OBSTETRICS | Comments Off on Increased Nuchal Translucency

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