Contribution of the Exome Sequencing in Antenatal Period Behind Ultrasound Features Suggestive of a Rare Genetic Disease

Congenital malformations concern 3% of pregnancies; most of them can be seen during pregnancy. For some malformations, an invasive sample (trophoblast biopsy or amniocentesis) is proposed to search a chromosomal abnormality by the technique of DNA chip. However, some strongly suggestive signs of a genetic (and not chromosomal) pathology have a very low diagnostic rate with this technique. In the absence of an etiological diagnosis, the prognosis for the unborn child is very difficult to assess, as we can't know if the fetal malformation is really isolated or associted to other unseen features as part of a syndromic condition.

For some malformations strongly suggestive of a genetic condition, we propose to realize an exome (i.e. all coding parts of the genome) sequencing of the trio (child and the 2 parents) with a delivery time compatible with the emergency situation of a pregnancy (6 weeks maximum). We will apply bioinformatics filters to analyse only genes known to be involved in the malformation present in the unborn child and thus avoid the identification of variants in unrelated genes. These lists of genes have been previously validated by the Rare Disease Health Sectors and the affiliated diagnostic laboratories. The selected malformations are: 1) anomalies of the central nervous system (microcephaly (<- 2DS) with anomalies of gyration, anomalies of the posterior fossa, anomalies of the midline except agenesis of the corpus callosum), 2) ophthalmological anomalies (microphthalmia, hyperplasia vitreous) and 3) renal abnormalities (large hyperechoic kidneys).