Chapter 18 - Preconception and Prenatal Screening and Diagnosis

Abstract

The goal of preconception and prenatal screening and diagnosis is to inform women and couples about the risks for genetic disorders and birth defects in their fetus during a future or ongoing pregnancy. In recent years, advances in technology have led to new cost-effective strategies for preconception genetic screening, preimplantation genetic testing, and sensitive prenatal aneuploidy screening. In parallel, high-throughput sequencing allows for prenatal testing for single-gene disorders by gene panel and exome sequencing. Women and couples should be counseled about their reproductive genetic risks and available testing and screening options, including carrier screening, before a pregnancy. This allows them to make informed decisions about testing and management options they wish to pursue in case of an abnormal or high-risk test result. When an increased risk for having a child with a significant birth defect or genetic disorder is discovered before pregnancy, in vitro fertilization with preimplantation genetic testing is available to prospective parents. When the increased risk is discovered during pregnancy, prenatal genetic diagnosis can confirm the presence or absence of the genetic disorder in the fetus. This requires a diagnostic procedure, usually chorionic villus sampling or amniocentesis. If the fetus is found to be affected, parents and providers can use this information to plan for appropriate prenatal, perinatal, and neonatal management, psychological preparation, early postnatal treatment, in some cases prenatal treatment, and some parents may choose to terminate the pregnancy. Absence of the genetic condition in the fetus will provide reassurance. The purpose of this chapter is to discuss the different approaches to preconception and prenatal screening and diagnosis and to review currently used methodologies and indications in this rapidly changing field.