Down syndrome — the fetus has one extra copy of a 21 chromosome. The severity of the disease ranges widely; heart defects and blood cancers are pretty common. The babies usually survive to adulthood. Edwards syndrome — is caused by the third copy of an 18 chromosome.
Babies with Edwards syndrome usually don't survive more than one year of life. Patau syndrome — caused by extra genetic material accumulated in a tripled 13 chromosome. Babies affected usually die within the first year of life. The fetus has 45 chromosomes, instead of the typical 45 — one of the chromosomes is missing. Our CRL and NT calculator uses the NT scan results chart presented below; all the values given in a table's body describe the thickness of a nuchal fold, given in millimeters mm.
To get the normal range of nuchal translucency at a given gestational age, you need first to convert CRL into the gestational age — you may compute it easily using our crown-rump length CRL calculator. Of course, the nuchal translucency measurement calculator is not the only tool needed to properly assess both the pregnancy course and the growth of your baby :.
Remember, it's totally alright if your child's NT is a little higher or lower than the expected value. All the NT measurements below the 95th percentile are considered normal. Take a look at the nuchal translucency measurements chart presented below; as you can see, the greater the nuchal fold thickness, the greater the risk of a genetic disorder, major abnormalities, and death.
Abnormal nuchal translucency begins at the 95th percentile — however, the risk rises significantly with much larger NT measurements. Embed Share via. Table of contents: What is the nuchal translucency test? Diseases connected to the abnormal nuchal fold Percentile charts for the nuchal translucency calculator — nuchal translucency measurement chart How to calculate the expected nuchal translucency?
Nuchal translucency risk table. The concentrations of the markers vary with gestational age. In the second trimester AFP and uE3 increase, hCG decreases, and inhibin decreases before 17 weeks and increases after 17 weeks.
Also, the measurement of serum markers may vary between laboratories. In order to take account of this variation, the concentration of each marker is expressed as a multiple of the median for unaffected pregnancies of the same gestational age MoM. In the diagram below the median marker level is 2. If a woman is found to have 5. Similarly if the level is 5. The graphs below show the overlapping relative frequency distributions of the markers in Down's pregnancies.
For a 75K PDF showing all six curves more clearly, please click any graph above. The serum marker levels are raised in twin pregnancies. Adjustments are made to take account of this.
Screening in twin pregnancies poses a difficulty because of the possibility that one fetus may be affected and the other may not. Neither the Nuchal Translucency Quality Review Program, the Perinatal Quality Foundation, nor any other individual or organization party involved in the preparation or publication of this site shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any use of or reliance upon this material. Maternal age-specific risk is obtained from a meta-analysis of birth prevalence 4 and adjusted to mid-trimester 5.
NT Calculator Disclosure. Please read the following terms and conditions and indicate your agreement before continuing. Cuckle H, Benn P. Ultrasound Obstet Gynecol ; Br J Obstet Gynaecol 82 9 ,
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