Читать книгу Protocols for High-Risk Pregnancies - Группа авторов - Страница 104

Carrier screening is defined as testing performed on individuals to assess whether they carry one allele for a genetic condition for which they do not have the phenotype. The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be provided information about carrier screening. Ideally, this carrier screening is performed prior to conception to maximize reproductive options and facilitate decision making. Ethnic, panethnic, and expanded carrier screening are all acceptable strategies for carrier screening. ACOG recommends that each obstetrician‐gynecologist or healthcare provider should establish a standard approach to screening. Historically, screening has been offered based on the individual’s pretest risk of carrier status as determined by her racial or ethnic background or her family history. However, in an increasingly multiethnic society, such targeted strategies are being supplanted by panethnic screening algorithms.

With the advent of lower cost, high‐throughput genotyping technology, expanded carrier screening panels that evaluate for hundreds of conditions are being introduced. ACOG has recommended the following screening criteria for disorders that should be included in expanded panels. Carrier frequency should be 1 in 100 or greater, corresponding to a disease incidence of 1 in 40 000. The phenotype associated with the condition should be well defined, occur early in life, and cause significant physical or cognitive impairment or affect quality of life. The condition will ideally be amenable to prenatal diagnosis, changes to antenatal or delivery management, and parental education about coordination of care after delivery. In contrast to diseases for which newborn screening is mandated, carrier screening is offered for lethal conditions such as Tay–Sachs disease that do not necessarily have postnatal intervention strategies.

The purpose of this chapter is to review specific genetic conditions for which carrier screening is most commonly offered. We review the clinical significance, cause, and screening recommendations for each condition.