Prenatal Diagnosis: A critical review of methods

Abstract

Prenatal diagnosis allows identification of developmental malformations and possibilities of genetic diseases in foetus during the pregnancy. Prenatal diagnosis has traditionally relied on two main modalities to identify abnormalities of fetal development: invasive and noninvasive. These tests help in taking decision about the pregnancy like chances of treatment, parent's acceptance of a handicapped child and to assess necessity of termination of the pregnancy. In prenatal testing, both screening and diagnostic procedures are included. Screening procedures like biochemical and/or ultrasound screening in first and second trimester are routinely practiced for pregnant women. A variety of approaches for genetic prenatal analysis are now available, including preimplantation diagnosis, chorion villi sampling, amniocentesis, fetal blood sampling as well as newer approaches like fetal cell and DNA isolation from maternal blood. Non-invasive methods are highly accurate and risk-free tests that will identify fetal material in the maternal blood, and give more promising diagnosis. An incredible progress in new genetic techniques e.g. RAPID-FISH, MLPA, quantitative PCR, chromosome microarrays (CMAs) allow rapid results in prenatal diagnosis of aneuploidy. Advances in genomics allow whole genome sequencing and exome sequencing to deliver affordable and accessible, massive information to parents. Post-genomics technologies that explore the proteins (proteomics) and transcripts (transcriptomics) released by the placenta into the maternal circulation offer new opportunities to identify genes. Proteomic technologies enable newer approaches for discovering biomarkers from biological fluids through high-throughput technologies which improve the prediction of various fetal abnormalities. Multiple diagnostics methods are available for the parents to choose, for the prenatal screening to detect physical anomalies and genetic disorders in the fetus during the progress of pregnancies. Over the past decade, remarkable advancements in the field of prenatal diagnos-tics has been made but the need of the hour is to make such technologies accessible and economic to be used routinely in clinical settings. In the present review we are analysing the major invasive and noninvasive methodologies and their use in different prenatal diagnostics of various abnormalities and also how latest technologies including high throughput methods like whole genome sequencing exome sequencing, proteomics are proving to be highly accurate and precise methodologies for the diagnosis of fetal anomalies is becoming more precise. Informations from current literature are obtained through searching various databases to review and summarize invasive and noninvasive techniques practiced for prenatal diagnosis.