It is both safer and more complicated to be a pregnant woman today. Advances in medicine allow more abnormalities to be detected in the fetus, which opens up new possibilities for intervening at birth or deciding not to continue. But these advances are forcing couples to make choices that are all the more difficult as the tests include a large margin of uncertainty. The prenatal screening for trisomy 21, in particular, raises complex questions.
The High Authority for Health (HAS) indeed recommended, in May 2017, the person responsible for the cognitive delay. This test analyzing the free DNA of the fetus circulating in the mother’s blood has also been included on the official list of prenatal diagnostic examinations by a published in Official newspaper.
The information intended to enlighten couples on what they can expect by subscribing to one of the three existing screening tests is insufficient today, as regretted by (Ciane), representative of the users. For them, here are seven questions that it is useful to ask to see more clearly, and the answers that can be given in view of current knowledge.
Would I accept a child with Down’s syndrome?
The initial question to ask yourself is this: would I accept a child with Down’s syndrome or not? It is wise to think about it before going to the first consultation, screening for this anomaly being offered at the very beginning of pregnancy. In general, the doctor or the midwife leaves little time for the couple to reflect because the time slot provided in France for this consultation is only 30 minutes. Other European countries, given the multitude of topics to be discussed that day.
No one can answer this question for you. The degree of mental handicap associated with Down’s syndrome is variable, and cannot be predicted by any prenatal test. Some adults with this chromosomal abnormality have a quasi-autonomous existence, others do not. Associations of parents of children with Down’s syndrome provide testimonials on their sites, for example, or. The position of each, which may depend on a personal vision of existence or religious values, is respectable.
This is also the time to ask yourself questions about the termination of pregnancy. If you rule out the possibility of such an intervention, it is a priori useless to do the tests for trisomy 21 because there is no treatment for this anomaly – abortion is the only option. Some experts nevertheless recommend that couples excluding abortion take the tests anyway, with the idea of preparing themselves psychologically if the unborn child should be a carrier of the anomaly. In the event that this is not discovered until birth, some hospitals offer to abandon the child for adoption.
How will the doctor make my decision?
If you do not wish to do these screening tests, you must consider a second question: how will the doctor make my decision? In principle, he should not discuss it because screening is not compulsory, as stated in. Moreover, this screening can only be carried out if the pregnant woman has signed the consent form.
But in practice, some practitioners are surprised by a refusal and ask the pregnant woman to justify her attitude, as shown. In addition, one of the tests is done during the first-trimester ultrasound, and some practitioners do.
What tests will I be offered?
If you decide to do this screening, the situation is obviously different. And the question to ask is this: what tests will be offered to me? The standard procedure in France has so far consisted of doing so-called “combined” screening. It includes a blood test, called serum markers, to measure hormone levels in maternal blood. To this is added, during the ultrasound of the first trimester of pregnancy, a measurement of the thickness of the neck of the fetus. The combination of these two results with the age of the pregnant woman (an older age is a risk factor) allows calculating a rate, called risk of fetal trisomy 21.
When this risk is considered high, the practitioner suggests doing a diagnostic test, the only one that can determine with certainty whether the fetus is a carrier of trisomy 21. This consists of studying the chromosomes of the fetus (the analysis is called a fetal karyotype. ) from a sample of amniotic fluid called amniocentesis) or a tissue sample from the placenta called cordocentesis. Amniocentesis is performed using a long needle sticking the stomach through the skin; cordocentesis, similarly or vaginally. In a very small number of cases, these actions trigger a miscarriage in the days that follow. Although this risk is very low, the consequence is nevertheless dramatic, which is why we try to avoid such an examination as much as possible.
consists in verifying the presence of an excess chromosome 21 in the fetus by analyzing its DNA present in the maternal blood. It is said to be “non-invasive” because it is carried out from a simple blood test in pregnant women. The advantage of this test is that a negative result almost completely eliminates the risk of Down’s syndrome, which avoids having to proceed with the diagnostic test. On the other hand, in the event of a result indicating a high risk, this new test must be confirmed by the diagnostic test, just as with the traditional “combined” screening. Because it too has a margin of error.
What, then, are the best performing screening tests among the three available?
The new non-invasive test is the one that generates the fewest errors in screening for trisomy 21. The serum marker test often announces so-called false-positive results (warning of high risk, when the fetus is not a carrier of trisomy 21) and sometimes false-negative results (announcement of low risk, while the fetus is a carrier). The measurement of the neck of the fetus is more efficient than the serum markers and less than the non-invasive test.
Will I be able to do only the non-invasive test?
The decision rests with the Department of Health, but the answer should be no. This is not the procedure recommended by the associations of health professionals such as the Association des cytogenéticiens de langue française (ACLF) and the National College of French Gynecologists and Obstetricians (CNGOF). You should know that the non-invasive test is very expensive. It is therefore offered, for the moment, only to women who have passed the two classic screening tests (serum markers and neck measurement) and obtained a result with a risk considered high.
What number is my combined screening result considered to be high risk?
In France, in the standard combined screening procedure, the risk is considered to be high if it is greater than 1/250. For example, if it is 1/240, or 1/50. The 1/250 rate means that among 250 women with this result, only one is expecting a child with Down’s syndrome. The threshold used varies from country to country, as shown. The Netherlands has adopted a more restrictive threshold, 1/200, therefore retaining fewer women in the so-called high-risk category. In Great Britain, the figure is 1/150, retaining even fewer women.
In recent months, in certain hospitals or clinics in France, for example, those of the AP-HP, practitioners have introduced the new non-invasive test and simultaneously adopted a less restrictive threshold to interpret the result of the combined screening. They took the figure of 1/1000, one. This places more women in the high-risk category, to whom the new non-invasive test is offered.
The advantage of this change of threshold is to minimize the risk of passing, unintentionally, next to a case of trisomy 21. Its disadvantage is that the announcement of a high-risk result. It can cause great anxiety, which sometimes persists after a reassuring diagnostic test result, and. This anxiety can lead to depression and disrupt the mother’s relationship with the newborn.
How much do these three tests cost for couples?
The serum markers and theultrasound are reimbursed at 100% by health insurance. This is not the case, for the moment, with the non-invasive test. This should change if the recommendations of the HAS are endorsed by the Ministry of Health and lead to its coverage by health insurance. The non-invasive test is currently billed around 400 euros by biomedical analysis companies. The public assistance hospitals in Paris offer it free of charge.
Thus, the HAS recommendations are far from trivial for the 800,000 women who start pregnancy each year. By lowering the threshold defining the category of women at high risk of fetal trisomy 21, 30,000 more pregnant women will be notified of the possibility of an anomaly and offered the option of a diagnostic test, as indicated. in the HAS report. Such a device can be considered a breakthrough from a biomedical point of view because it increases the ability to detect fetuses with Down’s syndrome by screening. However, it carries low but not negligible risks, such as that of anxiety. and miscarriage for women newly included in the high-risk category.
Couples must be better informed of the benefits and risks associated with the different tests available, and at each stage have the choice of whether to ask for them or not. The worst would undoubtedly be that couples awaiting a child, under the pretext that the subject of screening has become too technical, rely entirely on the advice of experts and the medical profession on issues involving their future as parents.
of this article was posted in 2017.