The annual report of the Biomedicine Agency (ABM) makes the assessment of the “activity” of screening and prenatal diagnosis [1]. Unsurprisingly, trisomy 21 is still at the heart of the agency’s concerns.
In France, 738,000 “ live births were identified in 2021. But before being born, these babies were screened, in particular for trisomy 21.
« The examination concerning the greatest number of pregnant women is screening for trisomy 21 by maternal serum markers with 629,688 women[2] tested in 2021 », Specifies the ABM. A first step followed by a second screen: that of the DPNI. ” The prenatal examination activity is gradually evolving with an increase in the number of non-invasive examinations (from maternal blood samples) and the greater use of technologies with a more precise diagnostic resolution such as ACPA or sequencing techniques. High Speed “, points out the agency. An exam “Painless”. At least for the woman.
In 2021, 128,958 examinations were carried out by the 28 authorized centres. But of these 28 labs, “ 2 private laboratories carry out approximately 2/3 of the examinations “. Would the business be lucrative?
The reliability of screening in question
The number of fetuses diagnosed with trisomy 21 increased by 7.5% in 2021, from 2,045 in 2020 to 2,199 in 2021. The “sorting” is intended to be reliable.
807 NIPTs came back positive last year. On these 807 fetuses, the examination of the karyotype posed a diagnosis of trisomy for only 666 of them. In 17.4% of cases, the NIPT therefore proved to be a “false positive”. How many women will have aborted following an unfavorable screening, without waiting for diagnostic confirmation?
Conversely, the analysis of the data identifies 5 “false negatives”. Fetuses carrying trisomy 21, not detected by analysis of their DNA circulating in the maternal blood. In three cases, NIPT indicated trisomy 13 which turned out to be trisomy 21.” This data will be tracked “, assures the ABM. Are “false negatives” more worrying than “false positives”?
A decrease in the use of IMG
Diagnoses of trisomy 21 “discovered” at the birth of the child are, however, rarer. From 500 in 2017, there were only 390 in 2021. Children for whom the mother refused screening or diagnostic examinations, or even “false negatives”, slipped through the cracks.
A ” certificate of particular gravity for fetal reason can be issued for medical termination of pregnancy. Trisomy 21 represents more than a quarter of certificates last year[3]. But in 2.1% of cases[4], although a certificate was issued, the woman did not wish to abort. A rising number[5]. Here once more, the ABM promises a trace » (cf. Increase in infant mortality in France: various causes). Isn’t the woman free to choose?
[1] « From a legal point of view as from a medical point of view, the activity of prenatal diagnosis differs from the activity of prenatal screening. “, explains the ABM. Screening reports “ medical biology or imaging examinations to assess the risk that the embryo or fetus presents with a condition likely to modify the course or monitoring of pregnancy, mentioned in II of article L. 2131-1 “. They understand :
- Biochemical examinations on maternal serum markers;
- Obstetric and fetal ultrasound within the meaning of 1° of III of this article;
- Genetic testing of free fetal DNA circulating in maternal blood (also called non-invasive prenatal screening, NIPT)
The diagnosis is regarding him. medical biology and diagnostic imaging examinations mentioned in IV of article L. 2131-1 “. They understand :
- Cytogenetic examinations, including molecular examinations applied to cytogenetics;
- Molecular genetic tests;
- Fetal biochemical examinations for diagnostic purposes;
- Examinations for the diagnosis of infectious diseases;
- Obstetric and fetal ultrasound within the meaning of 2° of III of this article;
- Other fetal imaging techniques for diagnostic purposes.
For trisomy 21, screening means “ a set of specific clinical, ultrasound and biological procedures aimed at assessing the risk of fetal trisomy 21 during pregnancy and including, depending on the situation:
- screening ultrasound for the first trimester of pregnancy;
- a combined screening of the first trimester taking into account the nuchal translucency and cranio-caudal length measurements as well as the dosage of maternal serum markers (MSM) of the 1st trimester of pregnancy (recommended procedure) or, failing this, an MSM screening of the second trimester taking into account the dosage of serum markers of the 2nd trimester of pregnancy, preferably carried out from 15.0 SA;
- screening on free fetal DNA circulating in maternal blood (cDNAT21) carried out as a 2nd intention proposed according to the level of risk assessed by screening using MSM.
Only an invasive sample can make the diagnosis. »
[2] Or 85.3%, by relating this figure to the number of births. A rate that has increased rapidly ” since 2010.
[3] 1804 of the 7166 certificates issued in 2021
[4] 153 out of 7166
[5] It was 1.5% in 2019, with 106 “ IMG not performed »
