Antenatal Care Nuchal Translucency Nt Scan

Nuchal translucency (NT) scan is an ultrasound abdominal scan (sonographic prenatal screening scan) which is performed on pregnant women.  This scan is safe for both mother and the baby.  It is used to measure the thickness of nuchal translucency or nuchal fold.  Nuchal translucency is a collection of fluid under the skin at the back of the baby’s neck.  

Excessive accumulation of this fluid is a sign of Down’s syndrome (trisomy 21).  It is the most common genetic disorder.  Other chromosomal defects like triploidy, Turner syndrome, trisomy 13 and trisomy 18 cause thicker nuchal translucency.  Doctors use NT scan in cases where pregnant women are more than 35 years of age, in cases of high risk pregnancies and in cases of first time pregnancies.  NT scan may also be used to confirm pregnancy date.  It is observed that the risk of Down’s syndrome rises with maternal age.  In pregnant ladies less than 25 years of age, the risk is 1 in 1400.  But the risk is 1 in 350 in pregnant ladies who are 35 years of age and 1 in 100 in pregnant ladies who are 40 years of age.  

NT scan is usually performed between 11th to 14th week of pregnancy when the fetal lymphatic system would be developing and the peripheral resistance of the placenta would be high.  The pregnant woman should have the bladder full for this scan to be performed.  The baby is measured from head to spine.  Width of the NT is measured.  NT measurement of up to 2 mm is considered normal at 11th week.  NT measurement of 6 mm is considered as a sure sign of Down’s syndrome.  It is diagnosed further using other appropriate methods like CVS (Chorionic Villus Sampling), blood tests or amniocentesis.  But CVS and amniocentesis carry a risk of miscarriage.  High NT measurement may also indicate congenital heart defect.  The skin appears as a white line in the image.  The fluid under the skin will appear black.  The report will usually be available in less than 24 hours.  

NT scan is found to be fairly accurate in identifying Down’s syndrome.  Many private diagnostic centers perform NT scans.  But it is always safe to visit those centers which are suggested by a certified gynecologist.