PARIS -- Most karyotypically normal fetuses with elevated nuchal translucency at 11-14 weeks will be born without major abnormalities, Dr. Katia Bilardo reported at the 13th World Congress on Ultrasound in Obstetrics and Gynecology.
Sonographic assessment of nuchal translucency (NT) at 11-14 weeks' gestation is a recognized effective screening method for trisomy 21 and other chromosomal abnormalities. Up to 80% of aneuploid fetuses have increased NT, but so do 3%-5% of karyotypically normal fetuses, said Dr. Bilardo of the Academic Medical Centre, Amsterdam.
Over a 9-year period, 67% of 560 fetuses with elevated NT at 11-14 weeks had normal karyotypes. Of those 376, 81% were normal (detected by subsequent scans or after birth) while 19% had major adverse outcomes, including structural anomalies in 7.2%, spontaneous abortion/intrauterine death in 4.3%, genetic syndromes in 4.0%, and voluntary termination of pregnancy in 3.5%.
The likelihood of abnormality increased with NT thickness, from 8% with NT of 3.5 mm to 30% at 5.5 mm to 78% at 6.5 mm and above, she said at the conference, also sponsored by the International Society of Ultrasound in Obstetrics and Gynecology.
Cardiac defects--including ventricular and atrial septal defects, tricuspid atresia, and double outlet right ventricle--were diagnosed in 13 fetuses/infants, a finding that parallels the experience of other groups.
NT may also be a way to screen for major heart defects, Dr. Bilardo said.
Of 312 surviving fetuses who had normal second scans at 20 weeks, just 3% were born with abnormalities.
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