Increased nuchal translucency in fetuses with a normal karyotype.

Sonographic assessment of nuchal translucency (NT) thickness has been recognized as an effective means of screening for trisomy 21 and other chromosomal abnormalities at 11–14 weeks of gestation. Up to 80% of aneuploid fetuses have increased NT, but this feature is also found in 5% of karyotypically normal fetuses at this stage of pregnancy (Snijders et al., 1998). As this screening test examines the fetus directly, many parents equate a high-risk result with fetal abnormality more readily than screening by other techniques. Typically giving the news that the fetal karyotype is normal is followed by the question ‘So what is wrong with my baby?’ As the use of first trimester ultrasound, and in particular screening by NT thickness, becomes more widespread it is important to develop a strategy for the further management of these pregnancies which will enable us to identify other associated anomalies at an earlier stage. Parents need to be aware that the majority of fetuses with increased NT and a normal karyotype will have a normal outcome. This information, together with a discussion about the plan for subsequent management, should help them to continue the pregnancy with confidence and avoid choosing to terminate on the basis of an ultrasound marker rather than the identification of a fetal abnormality.