Prenatal Diagnosis

The goal of this observational study is to learn if whole-genome sequencing (WGS) can help find the genetic cause in fetuses with structural abnormalities that remain unexplained after standard genetic testing (such as karyotyping, chromosomal microarray, or whole-exome sequencing). It will also learn how WGS results may affect pregnancy management and family decision-making. The main questions it aims to answer are: How often does WGS identify a genetic cause in these fetuses? Does WGS find more genetic causes compared to standard genetic tests? Can combining WGS with other molecular analyses help discover new disease genes or pathways? Researchers will compare WGS results to results from standard genetic tests to see if WGS finds more genetic causes. Participants are pregnant women whose fetuses have structural abnormalities seen on ultrasound or MRI, with negative results from routine genetic testing. Participants will: Undergo an invasive procedure (such as amniocentesis) or provide postnatal samples as part of their regular medical care Allow the use of leftover samples for WGS and additional molecular studies Be followed until after delivery to collect information on pregnancy outcomes and neonatal health

In the context of intricate cases with ambiguous prenatal genetic diagnoses, this project intends to carry out long - read DNA sequencing data analysis on birth defect cases and family samples. The emphasis lies on the extraction and identification of individual - specific genomic characteristics, as well as the development of detection algorithms for all categories of structural variations (SV), including complex SV. It will establish a pan - genomic reference map specific to the Chinese population to facilitate the identification of pathogenic SV in birth defect cases and family samples of the Chinese population, and delineate the detailed SV spectrum of major birth defects in the Chinese population. Additionally, the project will conduct in - depth analyses of the genetic and pathogenic roles of different types of SV in birth defects, offering a theoretical foundation for promoting the early warning, intervention, and prevention of major birth defects in China.

Fetal brain MRI is an essential diagnostic tool to inform parents about the prognosis of abnormalities detected on routine ultrasound. Recent work has shown that brain MRI measurements at the antenatal stage are predictive of the child's postnatal development. However, this work remains limited to basic research, in part because of the lack of normative curves of brain tissue volume evolution from fetal MRI acquired in clinical routine. This project aims to fill this gap. For this purpose, the project will exploit fetal MRI scans acquired in 4 French hospitals (Marseille, Nice, Montpellier and Paris): MRI scans without abnormalities will be centralized for analysis, and families who have undergone these scans will be contacted to evaluate the development of their children after birth. Normative curves will be established by applying a set of treatments developed by the laboratory in Marseille collaborating in the project. Ultimately, these curves will help to clarify the diagnosis of fetuses by providing a quantitative characterization of the normality of brain measurements.