NT MoM Assessment
Enter crown-rump length (CRL) and nuchal translucency measurement to compute the expected median and MoM for first-trimester screening.
Valid for CRL 38–84 mm (11–13+6 weeks).
Median NT
6.42 mm
Calculated MoM
0.23
Approximate GA
16w 4d
How to Use This Calculator
Measure CRL accurately
Obtain a mid-sagittal image with the fetus neutral, measuring crown-rump length between 38–84 mm.
Acquire proper NT measurement
Zoom image, position calipers inner-to-inner at the widest NT area, and capture in end-diastole.
Interpret MoM results
Use MoM thresholds to decide on additional screening, cfDNA testing, or diagnostic procedures.
Formula
Median NT (mm) ≈ 0.126 × CRL0.96
MoM = Measured NT ÷ Median NT
Valid for CRL 38–84 mm (11–13+6 weeks). Adapted from Fetal Medicine Foundation reference data.
Full Description
Nuchal translucency measurement between 11 and 13+6 weeks is a cornerstone of first-trimester aneuploidy screening. Increased NT is associated with chromosomal abnormalities, congenital heart defects, and genetic syndromes. Converting NT to multiples of the median (MoM) facilitates risk stratification across gestational ages. Combine NT with serum markers (PAPP-A, free β-hCG) or cell-free DNA for comprehensive screening.
Frequently Asked Questions
What factors affect NT measurement?
Operator experience, fetal position, and image magnification influence accuracy. Ensure strict adherence to guidelines.
Does a normal NT eliminate all risk?
No. Some aneuploidies or heart defects occur despite normal NT. Combine with other screening modalities.
How often should NT be repeated?
Usually performed once in the first trimester. Repeat only if initial measurement was suboptimal.
Can NT be used after 14 weeks?
NT loses reliability after 13+6 weeks. Mid-trimester anatomy scan and cervical translucency assessments replace NT.