Between the tests that will be performed in pregnancy, if you wish, there are those of chromosomal abnormality detection. That the baby may suffer from a chromosomal defect is one of the parents' great concerns, so we will explain what prenatal tests are performed to detect them.
Although it has been announced the arrival in Spain of blood tests to detect abnormalities in the fetus in the first weeks of pregnancy, the truth is that it is a test that is not carried out massively and that is currently quite expensive, so that basically three are still used: the triple screening test as screening test, and invasive tests such as chorionic biopsy and amniocentesis.
Triple screening or triple test
It is a test that is performed in the first trimester, between the 10th and 13th week of pregnancy, which combines three parameters, hence its name: personal data (age, weight, number of fetuses, etc.), ultrasound measurement (nuchal fold) and three biochemical markers present in the mother's blood (PAPP-A, beta- HCG free and and estriol free).
Detects some chromosomal abnormalities such as Down syndrome, Edward syndrome, Turner syndrome, or Smithl-Lemli-Opitz syndrome and neural tube defects, among others.
The proof it is a screening, that is to say that it throws a risk. It does not mean that your child has a chromosopathy, but that you have a higher risk than others that your child has it. If the result yields 1: 150, it means that there is a chance in 150 of your baby suffering from any, when normal is one in 10,000. Here you have more information on how to interpret the values.
When the values are less than 1: 250 it is recommended to perform a chorionic biopsy or an amniocentesis to obtain more conclusive data. In my opinion it is a double-edged sword, because it can unnecessarily worry the mother and subject her to unnecessary stress (I say it from experience). In the case of following medical advice you can undergo an invasive test with a risk of abortion, minimal, but existing. Therefore, you have to be well informed to know what to expect from the test and decide what you want to do.
Corion biopsy or chorionic villus biopsy
Is done between weeks 11 and 13 of pregnancy and it consists of introducing a needle to extract a sample of the chorionic villi that are cells that are part of the placental tissue to analyze them in the laboratory.
Chorionic villus analysis (CVS) is performed transcervically, that is, through the cervix or if it is not accessible, through an abdominal puncture with local anesthesia. At the same time, an ultrasound is performed, which allows visualizing the maternal and fetal structures to ensure that the biospia is done well and without problems.
It is used to detect chromosomal and DNA abnormalities before amniocentesis, since this is done later, but does not detect abnormalities such as neural tube defects, but amniocentesis itself. It presents an abortion risk close to 1% percent.
It is recommended, for example, in case of increased nuchal translucency, if the mother is over 35 years of age or has a previous child or pregnancy with any chromosomal or other alteration. The results take approximately 48 hours.
Amniocentesis
It is believed that along with the previous one it is a test that will tend to disappear, but for the moment it is the one used to have a confirmation with almost 100 reliability.
Is done around week 15 of gestation and consists of extracting by means of a abdominal puncture a sample of amniotic fluid surrounding the fetus
From this liquid, different components are obtained, such as alpha-fetoproteins, cells and DNA that are analyzed in the laboratory in order to detect different anomalies such as Down, Edwards or Turner's syndrome, among others.
It is a safe test, but it carries certain risks. The most prominent is spontaneous abortion after the test, which occurs in approximately 1% of cases. Other possible risks are fetal or cord puncture during the test, as well as infection or bleeding of the pregnant woman in the period after performing the technique.
Since it is necessary to perform a culture of the cells for an approximate period of 14 days, the results can take between three and four weeks.
Photos | Daquella Manera and Daquella Manera on Flickr
