12 Weeks Nuchal Ultrasound Scan

The nuchal translucency scan is a detailed 12-week ultrasound that measures the fluid at the back of your baby’s neck (nuchal translucency) to assess the risk of Down’s syndrome and other chromosomal conditions. Performed between 11 weeks + 2 days and 14 weeks + 1 day, this scan also includes detailed measurements of your baby’s crown-rump length (for accurate dating), checks major organs forming, and assesses early anatomy.

Combined with blood tests (if requested separately), this provides your personal risk score for chromosomal abnormalities. Our specialist sonographers are highly experienced in nuchal scans and work to Fetal Medicine Foundation standards.

You’ll receive clear explanations, measurements, photos, and a detailed report. Available at our Brentwood clinic for expectant parents throughout Essex.

What’s Included:

Nuchal Translucency (NT) Measurement:

• Fluid measurement at back of baby’s neck
• Precise measurement to 0.1mm
• Most important part of scan
• Measured with baby in specific position
• Compared to normal ranges for gestation

Crown-Rump Length (CRL):

• Baby measured from head to bottom
• Confirms accurate dates
• Refines due date if needed
• Essential for NT interpretation

Nasal Bone Assessment:

• Checks if nasal bone is present
• Absence increases risk
• Part of comprehensive assessment
• Not all hospitals check this

Early Anatomy Check:

• Brain structures (basic view)
• Heart (4-chamber view if possible)
• Stomach bubble
• Bladder
• Limbs (arms and legs)
• Spine (basic assessment)
• Abdominal wall

Other Assessments:

• Heart rate measurement
• Placenta location (early view)
• Number of babies confirmed
• Amniotic fluid assessment
• Uterus and cervix check

Detailed Report:

• All measurements recorded
• NT measurement and percentile
• CRL and confirmed dates
• Risk assessment explanation
• Images included

Critical Timing Window:

Exact Dates Required:

• 11 weeks + 2 days to 13 weeks + 6 days
• Very narrow window
• Outside these dates, NT measurement invalid
• Based on CRL measurement, not LMP dates

Why Timing Matters:

• NT changes with gestation
• Too early: Too small to measure accurately
• Too late: Fluid disperses naturally
• Must be measured at exact right time

Book Early:

• We recommend booking at 8-9 weeks
• We’ll schedule exact appointment date
• We may need to adjust date after early scan
• Don’t leave it too late!

What We Measure:

Nuchal Translucency (NT):

• Normal: <3.5mm at 12 weeks
• Borderline: 3.5-4.5mm
• Increased: >4.5mm
• Varies with gestation (larger baby = slightly thicker NT)
• Measured three times, best measurement used

Nasal Bone:

• Present: Reassuring sign
• Absent: Increases risk
• Hypoplastic (small): May increase risk
• Part of overall picture

Ductus Venosus (Blood Flow):

• Not always measured routinely
• Specialized Doppler assessment
• Flow pattern assessed
• Abnormal flow increases risk

Tricuspid Valve:

• Heart valve assessment
• Regurgitation (leakage) increases risk
• Specialist measurement
• Not all clinics assess this

Risk Assessment:

What the Scan Shows: This scan does NOT diagnose chromosomal conditions. It provides a RISK ASSESSMENT only.

Combined Screening: When combined with blood test (done separately):

• First Trimester Combined Test
• Blood tests: PAPP-A and free β-hCG
• Combined with: NT, nasal bone, maternal age
• Result: Personal risk score

Example Risk Scores:

• 1 in 10,000: Very low risk (reassuring)
• 1 in 1,000: Low risk
• 1 in 250: Screen positive threshold
• 1 in 100: Higher risk
• 1 in 10: High risk

Interpreting Results:

Low Risk (<1 in 150):

• Reassuring result
• Continue routine antenatal care
• No further tests needed
• Standard 20-week scan

Intermediate Risk (1:150 to 1:50):

• Borderline result
• Consider NIPT (non-invasive blood test)
• Discuss with midwife/obstetrician
• Decision about further testing

High Risk (>1:50):

• Suggests increased likelihood
• Doesn’t mean baby has condition
• Options for further testing:
  • NIPT (Non-Invasive Prenatal Testing)
  • CVS (Chorionic Villus Sampling)
  • Amniocentesis (later)
• Genetic counselling offered

Important Understanding:

Risk is NOT Diagnosis:

• High risk doesn’t mean baby affected
• Many high-risk babies are completely healthy
• Low risk doesn’t guarantee normal
• It’s a probability, not certainty

Example: Risk of 1 in 50 means:

• 1 in 50 babies with this risk has the condition
• 49 in 50 babies with this risk are normal
• Still 98% chance baby is unaffected

What Affects NT Measurement:

Normal Variations:

• Baby’s position (must be specific)
• Maternal BMI (harder to measure if overweight)
• Uterine position
• Quality of ultrasound image
• Sonographer experience

Increased NT Can Indicate:

• Chromosomal conditions: Down’s, Edwards, Patau syndromes
• Heart defects: Even without chromosomal issues
• Other genetic syndromes
• Sometimes normal variant

Follow-Up if NT Increased:

Even with Normal Chromosomes:

• Detailed cardiac scan at 16-18 weeks
• Growth monitoring
• Detailed anomaly scan at 20 weeks
• Most babies with increased NT are healthy

Conditions Assessed:

Main Chromosomal Conditions:

Down’s Syndrome (Trisomy 21):

• Most common chromosomal condition screened
• NT often increased
• Nasal bone may be absent
• Blood markers abnormal

Edwards Syndrome (Trisomy 18):

• Severe chromosomal condition
• Very high NT common
• Other abnormalities often visible
• Poor prognosis

Patau Syndrome (Trisomy 13):

• Severe chromosomal condition
• Increased NT possible
• Often other abnormalities visible
• Poor prognosis

Other Conditions:

• Turner syndrome
• Triploidy
• Cardiac abnormalities
• Some genetic syndromes

The Scan Process:

What Happens:

• Lie on examination couch
• Gel applied to abdomen
• Scan takes 20-30 minutes
• Baby must be in correct position
• May need to wait for baby to move
• May need gentle abdominal pressure
• Some walking/jiggling may be needed

Baby Position Required:

• Neutral position (not curled up)
• Profile view clear
• Not moving during measurement
• Correct angle for NT
• May take time to achieve

Measurements Taken:

• Three NT measurements (best one used)
• CRL measured
• Nasal bone checked
• Other markers assessed
• Images captured

What You’ll See:

• Baby in profile
• Heartbeat
• Movement
• Early features (head, body, limbs)
• Amazing detail even at 12 weeks!

Photos Provided:

• Several images of baby
• Measurement images
• Profile views
• Images you can share

After the Scan:

Same Day:

• Results explained immediately
• Measurements discussed
• Risk level explained (if blood test done)
• Photos provided
• Report given

If Blood Test Needed:

• Can often be done same day elsewhere
• Results in few days
• Combined result calculated
• GP/midwife informed

Next Steps:

All Results:

• Continue with routine antenatal care
• Book 20-week anomaly scan
• Discuss any concerns with midwife

If High Risk Result:

• Counseling about options
• NIPT can be arranged
• Diagnostic testing discussed (CVS/Amniocentesis)
• Support provided
• Not left uncertain

No Special Preparation:

• No fasting required
• Moderately full bladder helpful
• Comfortable clothing
• Bring partner/support person
• Bring maternity notes

Important Reminders:

This is Optional Screening:

• You can choose not to have it
• Some prefer not to know risk
• Personal decision
• No pressure either way

Results Can Cause Anxiety:

• High risk results are worrying
• Most babies are fine even with high risk
• Difficult decisions may need to be made
• Support available

Not Diagnostic:

• Only CVS or amniocentesis diagnose for certain
• NT scan gives risk only
• Further tests needed for diagnosis
• Your choice whether to proceed

Accuracy:

Detection Rates:

• Combined screening (NT + blood): Detects 85-95% of Down’s syndrome cases
• NT alone: Detects 75-80%
• False positive rate: About 5% (5 in 100 low-risk pregnancies show high risk)

Limitations:

• Cannot detect all abnormalities
• Not all chromosomal conditions screened
• Other conditions not detected
• 20-week scan still essential

Cost Consideration:

• NT scan available
• Blood test may be separate
• NIPT is additional if needed
• Private diagnostic tests if chosen

Why Choose Private NT Scan:

Advantages:

• Convenient appointment time
• More time with sonographer
• Detailed explanation
• Better images often
• Immediate results discussion
• Complementary to NHS care

NHS Still Provides:

• Free NT scan at 12 weeks
• Combined screening
• Follow-up if needed
• Our scan is additional option