Nuchal Traslucency » What changes for pregnant women?
It is becoming increasingly apparent that an integrated first hospital visit at 11-13 weeks combining data from maternal characteristics and history with findings of biophysical and biochemical tests can define the patient-specific risk for a wide spectrum of pregnancy complications, including miscarriage and stillbirth, preeclampsia, gestational diabetes mellitus, preterm delivery, fetal growth restriction and macrosomia.
The diagnosis of Down syndrome, was made possible with the study of the number of chromosomes in the amniotic fluid.
Given that amniocentesis carries a risk of miscarriage, it soon became evident that it could not be offered to all pregnant women. Therefore it was initially decided to offer it to all those with higher risk based on maternal age, hence to all women above 35 years of age. However the reliability of this criteria is only 30%, which although gives some indication is a generic criteria and does not reflect the personal circumstances of the patient.
Therefore in 2000 it was deemed necessary to introduce the assessment of individual risk, which takes into account the age of the mother, measurements of hormones in the mother’s blood and ultrasound findings of specific indicators in the fetus, which vary in cases of chromosomal abnormalities (nuchal translucency, nasal bone, facial angle, cardiac valves, ductus venosus).
With individual risks, the detection rate of pregnancies that carry a higher risk of fetuses with chromosomal abnormalities, which would subsequently be referred for invasive procedures, is 95%. This is almost 3 times higher than the detection rate based on maternal age risk alone and therefore more reliable than what was used in the past.
Accordingly in Italyas in many other countries it will no longer be possible to offer invasive procedures based on maternal age but on individual risk. (National Guidelines 2010)
Using a recent method (2012) based on the analysis of fetal fraction of DNA present in the maternal blood, it is now possible to perform a non invasive test (NIPT=non invasive prenatal testing) for trisomies with excellent results. With this method, it is possible to identify in one blood test >99% of trisomy 21 with only <1% false negatives. (References, 16 December 2012)
This test is still not a substitute for villocentesis/amniocentesis. If the test is positive, it is still advisable to confirm with an invasive procedure.
This test available in Europe it is based on very recent developments, currently very expensive and requires the application of new technologies.
However, this recent development does not change the reliability of the screening based on nuchal translucency, as this is not solely limited to the detection of trisomies, but a diagnostic test for other morphological anomalies that can only be detected with ultrasound scan. Moreover in the first trimester, when the nuchal translucency can be analyzed, the principal risk factors and possible pregnancy complications can also be detected.
Most of the major researches were carried and coordinated at King’s College Hospital in London, under the supervision of Professor Kypros Nicolaides, the director of the Fetal Medicine Foundation (FMF)
The founder of this website contributed to the development of the first trimester screening, by conducting a study of the most complex organ: the fetal heart. This study, which was conducted both in Italy and Kings College Hospital in London, required the use of equipments and methodology considered most effective by international standards.(References)
At the time of the gestation when the nuchal translucency screening can be carried, the fetal heart as well as most of other major fetal defects (80%), are fully formed. Fetal heart malformation is the primary cause of prenatal death caused by congenital abnormalities. Congenital heart disease is the most frequent fetal malformation (compared to chromosomal defects, it has twice as much likelihood of occurrence).
The diagnosis of congenital heart diseases in fetuses increases the prognosis.
During the first trimester, it is also possible to evaluate specific risks for every pregnant woman against the major pregnancy complications (pre-eclampsia, miscarriage, premature birth).
The outcome of this evolution, which leads to an early diagnosis of chromosomal defects, pregnancy complications and fetal morphological analysis during the first trimester of pregnancy, makes the first trimester screening the most important examination during the course of a pregnancy.
Patients identified by the examination carried at 12 weeks as high risk for major complications, will be monitored closely and more frequently.
Most patients classified as low risk, will be able to avoid unnecessary routine checks.
In Italy the guideline of the Istituto Superiore di Sanità released in December 2011 in Italy, endorses this strategy, which has its foundation in the need to provide medical professionals and women going through pregnancies, easily accessible information on available tests that will then enable them to choose the appropriate course of treatments suitable for different circumstances.