(Early Detailed Anatomy Scan, Risk Calculation for Chromosomal Disorders, especially for Down Syndrome, Screening for Preeclempsia)
 

It has been in use since the beginning of 2000s and has been validated with many clinical trials. It can be performed  on fetuses  with Crown-to- Lump (CRL) measurement  between 45-85 mm. It is possible to capture 50% of serious structural disorders and approximately 90% of chromosomal disorders, especially Down's syndrome. 

 

The following evaluations and measurements are made:

* Fetal Heart activity

* Fetal movements

* Placenta location

* The amount of amniotic liquid around the fetus 

* Crown-Lump distance

* Head and body integrity

* Formation of cranial bones and intracranial structures

* Body contours

* Two arm-hands and two leg-feet

* Stomach

* Urinary Bladder

* Nuchal translucency (NT): In these weeks, all fetuses have a physiologic collection of thiny  fluid beneath the neck skin. The thickness of this fluid is measured. Significant increase in this thickness, increases the risk of both chromosomal and some structural disorders. However, a significant proportion of cases with increased nuchal translucency are normal. Although the nuchal translucency limit value varies according to the size of the fetus, 3.5 mm and bigger measurement  is a barely increased measurement( Above 2 SD - More than 95 centile) for all fetuses between 11-14 weeks , and requires a diagnostic tests without additional screening tests.

* Presence of Nasal Bone: In about half of babies with Down Syndrome, the nasal bone does not develop or very small.

* Examination of the vessel that carries the oxygenated blood from the umbilical cord through the liver (Ductus Venozus) using color doppler before it reaches the right atrium of the heart.

After the ultrasound examination, blood is taken from the mother for the Double Test on the same day and serum levels of two hormones secreted from placenta ; free beta hCG and PAPP-A, are measured.

For the Risk Asessment of Down Syndrome and other common chromosomal disorders; following parameters are used;

• Ultrasonography findings

• Double test values

• Maternal age, weight and height, smoking habit

• Presence of diabetes

• In vitro Fetilisation 

• History of chromosomal disorder in previous pregnancy

 

The data is processed in a computer program to obtain a risk assessment specific to this pregnancy. As a result of this evaluation, the expectant mother is seperated into high or low risk group according to the limit value taken (Generally, the limit value is 1/250). This test, which combines all the data, is called the Combined Screening Test.

 

If we can apply a definitive test (Amniocentesis or CVS) to all mothers in the high-risk group, it is possible to diagnose 90% of fetuses with Down's syndrome.  If we want to know for sure about the chromosol count of the fetus we need to obtain  a fetal cell and examine it in the genetic laboratory. This is possible either by taking a sample from liquid around the fetus  (Amniocentesis) or by biopsy (CVS) from the placenta . Both interventions should only be applied to the increased risk group, as they have some minor risk of abortion

 

11-14 weeks Screening Certification is mastered by  Fetal Medicine Foundation

(Fetal Medicine Foundation-FMF). 

The Fetal Medicine Foundation is a Registered Charity that aims to improve the health of pregnant women and their babies through research and training in fetal medicine.

The Foundation, with the support of an international group of experts, has introduced an educational programme both for healthcare professionals and parents and a series of certificates of competence in different aspects of fetal medicine.

In the last 20 years, The Foundation has supported research and training in the following areas through grants to a total of more than £23 million:

Early diagnosis of fetal abnormalities

Screening for chromosomal defects

Development of safer techniques for prenatal diagnosis

Intrauterine fetal surgery

Prediction and prevention of preeclampsia

Prediction and prevention of preterm birth

Prediction and prevention of stillbirth

Prediction and management of fetal growth restriction

Problems of multiple pregnancies

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To view the list of sonographers who have obtained the FMF Certificate of competence in measurement of nuchal translucency; plese click here https://fetalmedicine.org/lists/map/certified/NT