Pregnancy outcome and long-term follow-up of fetuses with isolated increased NT: a retrospective cohort study.

Objective: To assess the prevalence of associated findings, diagnosed either prior to or after birth, among fetuses with increased nuchal translucency (NT) and normal karyotype and to investigate the prevalence of children under therapy at school age, among cases confirmed to be isolated both prior to and after birth.

Methods: Retrospective cohort study of all singleton pregnancies were referred for the 1st trimester screening for Down syndrome between January 2004 and December 2006. Cases with NT >95th percentiles who undertook fetal karyotype were analyzed. We evaluated the prevalence of the following: (i) abnormal fetal karyotype, (ii) associated structural abnormalities, (iii) genetic syndromes, and (iv) children needing treatment (i.e. medications or psychopedagogical intervention) at school age.

Results: There were 19 106 women screened for Down syndrome. Among them, 846 (4.4%) had a NT >95th centile, of whom 541 (64.0%) undertook fetal karyotyping, 422 (78.0%) had normal karyotype, two (0.5%) opted for termination of pregnancy, and four (1.0%) ended in miscarriages. Among the 384 cases thought to be "normal" prior to birth, 14 (3.6%) were lost at follow-up and 10 (2.7%) had an associated abnormality diagnosed postnatally. Among the cases confirmed to be isolated, 10/270 (3.7%) were under treatment at the time of telephonic interview with parents.

Conclusions: Parents should be informed that fetuses with increased NT and normal karyotype need detailed ultrasound scans during pregnancy and detailed pediatric evaluation at birth; if these are normal, the risk from adverse outcome at school age is the same as for general population.