Multicentric Prospective Study to Screen Inborn Errors of Metabolism in Non-immune Hydrops (NIH) Fetalis by Massively Parallel Sequencing

Overview

A fetal hydrops, also called a fetal anasarca, is the buildup of fluid in the serosa and / or fetal subcutaneous tissue. The diagnosis is made by ultrasound, possibly from the first trimester of pregnancy. The etiologies of hydrops can be immune or non-immune. The historically classic immune causes are linked to fetal-maternal alloimmunizations in erythrocyte blood groups. The implementation of systematic prevention of these anti rhesus immunizations since the 1970s has significantly reduced the incidence of immune hydrops Non-immune hydrops (NIH) now represent 90% of fetal hydrops. Known causes of NIH can be classified in several ways depending on the mechanism or organ involved. The prognosis for NIH is closely linked to the cause. Fetal anemia due to maternal-fetal infections can heal spontaneously or give rise to in utero transfusions. Cardiac rhythm abnormalities are accessible to medical treatment. Chylothorax compressions may benefit from in utero drainage, but chromosomal or metabolic causes cannot benefit from antenatal care. The term of pregnancy in which the hydrops is discovered also has an impact on survival, which however remains poor. In France, certain pathologies can be considered as particularly serious without the possibility of treatment and give rise to a request for medical termination of pregnancy. This possibility is subject to acceptance by two practitioners who are members of a multidisciplinary prenatal diagnostic center (CPDPN). This preliminary multidisciplinary reflection participates in the development of prenatal counseling with the greatest precision in diagnostic hypotheses. This prenatal advice is essential for a couple on the decision to make a pregnancy in progress but also for future pregnancies, given the 25% risk of recurrence due to the autosomal recessive mode of transmission. Thus the current screening strategy for inherited metabolic diseases on amniotic fluid is fragmented. The resulting subdiagnosis explains the objective of the study of using the new high throughput sequencing techniques (NGS) in this indication. This approach should make it possible to reduce the number of cases classified as idiopathic, to allow the parents concerned to receive suitable genetic counseling with a view to new pregnancies, and to refine the knowledge of the prenatal epidemiology of these pathologies.