Nuchal Translucency Screening (NT Scan)
First trimester ultrasound measuring fluid at back of baby's neck to assess risk for Down syndrome and heart defects.
📅 When Performed
Weeks 11-14
⏱️ Results Timeline
3-7 days for combined results
Overview
The nuchal translucency (NT) scan is a special ultrasound that measures the clear space in the tissue at the back of your baby's neck. Babies with chromosomal conditions like Down syndrome tend to have increased fluid in this area during the first trimester.
The NT measurement is combined with blood tests (measuring hCG and PAPP-A) to create the "first trimester combined screening." This screening provides an individual risk assessment for Down syndrome and trisomy 18.
The NT scan must be performed during a specific window (11-14 weeks) by a specially trained technician, as the measurement needs to be very precise. It's one of the earlier screening options available.
🎯 Purpose of Test
- •Screen for Down syndrome (trisomy 21)
- •Screen for trisomy 18 and trisomy 13
- •Assess risk for heart defects
- •Detect some other chromosomal abnormalities
- •Early screening option at 11-14 weeks
- •Combined with blood work for more accurate assessment
🔬 How It's Performed
- 1.Special ultrasound with precise measurements
- 2.Performed by certified sonographer or maternal-fetal medicine specialist
- 3.Measures fluid at back of baby's neck
- 4.Must be done between exactly 11 weeks 0 days and 13 weeks 6 days
- 5.Measurement accurate to within 0.1mm
- 6.Blood drawn same day for PAPP-A and hCG
- 7.Results combined with blood work and maternal age to calculate risk
👀 What to Expect
- →Standard ultrasound on belly
- →May need full bladder
- →Baby must be in specific position for accurate measurement
- →May take longer than regular ultrasound to get right image
- →Completely painless
- →Blood draw from arm
- →Results available in a few days to a week
- →Risk assessment provided, not diagnosis
✓ Normal Results
NT measurement under 3mm, combined screening shows low risk (less than 1 in 1000)
⚠️ Abnormal Results
- •Increased NT measurement (over 3mm)
- •High-risk screening result (greater than 1 in 250-300)
- •Offered diagnostic testing (CVS or amniocentesis)
- •Meeting with genetic counselor recommended
- •May need additional ultrasounds or fetal echocardiogram
- •High NT can indicate heart defects even if chromosomes normal
- •Further testing recommended but not required
⚠️ Risks & Considerations
- •No risks - non-invasive ultrasound
- •Anxiety from waiting for results
- •False positive results possible
- •May lead to unnecessary worry
- •Some women may choose invasive testing based on results
📝 How to Prepare
- →Schedule between 11-14 weeks exactly
- →May need full bladder for ultrasound
- →Bring support person if desired
- →Understand test provides risk assessment, not diagnosis
- →Consider whether you'll pursue diagnostic testing if high risk
- →Prepare questions for genetic counselor