Pregnancy outcome in fetuses with increased nuchal translucency and normal karyotype

This study was conducted to evaluate pregnancy outcome and mid- and long-term prognosis of cases with nuchal translucency > or =4 mm and normal karyotype.

Retrospective analysis of 160 cases who presented with a nuchal translucency > or =4 mm when the CRL was between 45 and 84 mm was undertaken. Cystic hygromas were excluded. When the karyotype was normal a detailed anomaly scan was performed at 20 to 24 weeks followed by serial ultrasound examination. Clinical examination of the neonates was performed by a paediatrician. Long-term follow-up was completed through a questionnaire filled in by parents, GPs and paediatricians.

160 fetuses had an NT > or =4 mm. 44.3% had an abnormal karyotype. Of the 55.7% with normal karyotypes, 74 % did not show any abnormalities on follow-up ultrasound scan. Mid- and long-term outcome was known in 91% of the cases. 6.4% had a malformation diagnosed only at birth. Among the normal neonates, 11.1% are considered to have a significant neurological handicap or orthopaedic problems at 12 to 72 months of age.

In an unselected population, NT > or =4 mm is associated with a high incidence of chromosomal and non chromosomal abnormalities. Even when the fetal karyotype and serial ultrasound examinations are considered to be normal, the risk of fetal malformation and developmental delay should not be underestimated.