Practice Bulletin No. 162

Abstract

Prenatal genetic diagnostic testing is intended to determine, with as much certainty as possible, whether a specific genetic disorder or condition is present in the fetus. In contrast, prenatal genetic screening is designed to assess whether a patient is at increased risk of having a fetus affected by a genetic disorder. Originally, prenatal genetic testing focused primarily on Down syndrome (trisomy 21), but now it is able to detect a broad range of genetic disorders. Although it is necessary to perform amniocentesis or chorionic villus sampling (CVS) to definitively diagnose most genetic disorders, in some circumstances, fetal imaging with ultrasonography, echocardiography, or magnetic resonance imaging may be diagnostic of a particular structural fetal abnormality that is suggestive of an underlying genetic condition.The objective of prenatal genetic testing is to detect health problems that could affect the woman, fetus, or newborn and provide the patient and her obstetrician-gynecologist or other obstetric care provider with enough information to allow a fully informed decision about pregnancy management. Prenatal genetic testing cannot identify all abnormalities or problems in a fetus, and any testing should be focused on the individual patient's risks, reproductive goals, and preferences. It is important that patients understand the benefits and limitations of all prenatal screening and diagnostic testing, including the conditions for which tests are available and the conditions that will not be detected by testing. It also is important that patients realize that there is a broad range of clinical presentations, or phenotypes, for many genetic disorders and that results of genetic testing cannot predict all outcomes. Prenatal genetic testing has many benefits, including reassuring patients when results are normal, identifying disorders for which prenatal treatment may provide benefit, optimizing neonatal outcomes by ensuring the appropriate location for delivery and the necessary personnel to care for affected infants, and allowing the opportunity for pregnancy termination.The purpose of this Practice Bulletin is to review the current status of prenatal genetic diagnostic testing and the evidence supporting its use. For information regarding screening for fetal aneuploidy, refer to Practice Bulletin No. 163, Screening for Fetal Aneuploidy.

Knowledge, Attitudes, and Practices of Women Toward Prenatal Genetic Testing

“…American College of Obstetricians and Gynecologists (ACOG), and Society for Maternal Fetal Medicine (SMFM), and the World Health Organization (WHO)-have advocated making NIPGS services accessible to all, or at least a much wide swath, of pregnant women, as soon as they begin prenatal care. [8][9][10] What is more, a recent WHO report 7 supports the feasibility of doing so, even in low-to middle-income population, so long as costs, cultural considerations, and public health objectives and options are carefully anticipated, balanced, and coordinated. This positioning and possibility is of extreme significance to Arab nations in the Eastern Mediterranean Region (EMR), wherein rates of several congenital abnormalities are among the leading causes of infant mortality, premature death, and disability-adjusted life years (DALYs).…”

“…6 Noninvasive prenatal genetic screening is especially well-suited to this imperative, as through unobtrusive, early risk assessment, it can enable families and health care workers to educate themselves, make deliberated but timely and informed choices, seek additional testing, and prepare emotionally or in other ways for the likely outcomes of their pregnancy or health needs of the child. 2,5,7,8 Based on these medical and psychological advantages, many leading maternal and child health authorities-including the American College of Medicine and Genomics (ACMG), Knowledge, Attitudes, and Practices of Women Toward Prenatal Genetic Testing 2…”

Congenital Heart Disease: Genetic Aspect and Prenatal and Postnatal Counseling

“…If the amniocentesis detects a chromosomal abnormality, advance cytogenetic testing may be warranted. These testing include FISH, chromosomal microarray and whole exome sequencing [93]. The next step in the counseling, should mention the possibility of chorionic villus sampling or amniocentesis, as this knowledge may help determine prognosis and guide postnatal care.…”

Assessment of second-trimester amniocentesis cases: 10-year experience of a tertiary center

“…When it is carried out in an experienced center, the rate of gestational loss related with the procedure varies between 1/300 and 1/1000 for amniocentesis and CVS. [7] The indications of amniocentesis may change. Amniocentesis may be recommended for those with advanced maternal age (>35 years), family history of genetic disease, women with the history of baby with anomaly, USG results showing fetal abnormalities, positive result in screening test for syndromic babies and positive results in free DNA (cfDNA) test, which is non-invasive prenatal test (NIPT) as the risk of fetal aneuploidy is increased.…”