The Relationship between Thickness of Nuchal Translucency and Down Syndrome in the First Trimester of Pregnancy

Various anomalies, especially Down syndrome impose heavy emotional and financial burden on families and communities by development of mental and behavioral retardation. The purpose of this study is to assess the value of Nuchal Translucency (NT) to diagnose Down syndrome in the first trimester of pregnancy. This prospective study was conducted through evaluating 102 pregnant women of 17-44 years old with gestational age of 11 to 13 weeks and 3 days, in a private radiology clinic in Zahedan during May 2008 to June 2010. All embryos were ultra-sounded by a radiologist, their NT and crown-rump length were measured. After birth, all infants were examined by a pediatrician and cases suspected with Down syndrome were diagnosed through karyotype test. The mean of NT was 1.62 mm. NT was above 1.7 mm for women older than 35 years and it was 3.1 to 3.8 mm for women older than 40 years. 6 out of 7 cases diagnosed postnatal with Down syndrome, had above 95% normal NT and 4 out of 7 mothers who had baby with Down syndrome, were older than 35 years. Through measurement of NT during 11th to 13th weeks of pregnancy and consideration of base risk factors, the possibility of Down syndrome can be assessed and necessary diagnostic evaluations can be performed for risky cases.