A beneficial consequence of screening for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness (NT) at 10-14 weeks is the early diagnosis of trisomy 18. In a multicenter study of 91,091 singleton pregnancies there were 106 fetuses with trisomy 18 and 83% were identified by NT screening. Trisomy 18 was also associated with early onset intrauterine growth retardation, decreased fetal heart rate and the presence of exomphalos.