Prenatal genetic evaluation of the anomalous fetus
- Neeta Vora, MD
Neeta Vora, MD
- Assistant Professor
- University of North Carolina School of Medicine
- Sarah Harris, MS, CGC
Sarah Harris, MS, CGC
- University of North Carolina School of Medicine
Approximately 3 percent of live births are affected by a major structural malformation . With advances in prenatal ultrasound, many of these anomalies are now identified before birth. The etiology is diverse and includes environmental factors, genetic factors, or a combination of both. (See "Birth defects: Approach to evaluation".)
As the landscape of genetic testing rapidly evolves, clinicians are often left with many questions about the most appropriate testing methods to use for their patients. We will present our recommendations for a reasonable approach for the genetic evaluation of an anomalous fetus.
FREQUENCY OF CHROMOSOME ABNORMALITIES IN ANOMALOUS FETUSES
The finding of a fetal structural anomaly increases the possibility of a chromosome abnormality or genetic molecular defect and should prompt further evaluation into genetic etiologies. The frequency of a chromosome abnormality depends on the specific anomaly, the number of anomalies, and the combination of anomalies identified . In several retrospective series of prenatally detected anomalies on ultrasound that prompted genetic studies, an isolated fetal anomaly was associated with fetal chromosomal abnormalities in 2 to 18 percent of cases; multiple anomalies were associated with a fetal chromosomal abnormality in 18.8 to 35 percent [2-6].
Our approach — We offer an invasive procedure for diagnostic testing to patients with structural fetal abnormalities on ultrasound examination (algorithm 1) . The goal is to determine whether there is a genetic etiology of the abnormalities and thus enable well-informed counseling about prognosis, reproductive options, obstetric and pediatric management, and recurrence risks.
The decision to undergo invasive testing is very personal and must be based on the individual patient's personal values and goals. Pretest counseling by a provider familiar with the suspected fetal diagnoses and with genetic testing options is necessary for patients to make informed decisions. Alternatives to invasive diagnostic testing include noninvasive screening and postnatal testing.
- National Center for Health Statistics. Birth defects monitoring program. www.marchofdimes.org/peristats (Accessed on February 29, 2016).
- Staebler M, Donner C, Van Regemorter N, et al. Should determination of the karyotype be systematic for all malformations detected by obstetrical ultrasound? Prenat Diagn 2005; 25:567.
- Halliday J, Lumley J, Bankier A. Karyotype abnormalities in fetuses diagnosed as abnormal on ultrasound before 20 weeks' gestational age. Prenat Diagn 1994; 14:689.
- van Zalen-Sprock MM, van Vugt JM, Karsdorp VH, et al. Ultrasound diagnosis of fetal abnormalities and cytogenetic evaluation. Prenat Diagn 1991; 11:655.
- Nicolaides KH, Snijders RJ, Gosden CM, et al. Ultrasonographically detectable markers of fetal chromosomal abnormalities. Lancet 1992; 340:704.
- Rizzo N, Pittalis MC, Pilu G, et al. Distribution of abnormal karyotypes among malformed fetuses detected by ultrasound throughout gestation. Prenat Diagn 1996; 16:159.
- American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 88, December 2007. Invasive prenatal testing for aneuploidy. Obstet Gynecol 2007; 110:1459.
- American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins—Obstetrics, Committee on Genetics, Society for Maternal–Fetal Medicine. Practice Bulletin No. 162: Prenatal Diagnostic Testing for Genetic Disorders. Obstet Gynecol 2016; 127:e108.
- Shaffer LG, Bui TH. Molecular cytogenetic and rapid aneuploidy detection methods in prenatal diagnosis. Am J Med Genet C Semin Med Genet 2007; 145C:87.
- de Wit MC, Srebniak MI, Govaerts LC, et al. Additional value of prenatal genomic array testing in fetuses with isolated structural ultrasound abnormalities and a normal karyotype: a systematic review of the literature. Ultrasound Obstet Gynecol 2014; 43:139.
- Hillman SC, Pretlove S, Coomarasamy A, et al. Additional information from array comparative genomic hybridization technology over conventional karyotyping in prenatal diagnosis: a systematic review and meta-analysis. Ultrasound Obstet Gynecol 2011; 37:6.
- Hillman SC, McMullan DJ, Hall G, et al. Use of prenatal chromosomal microarray: prospective cohort study and systematic review and meta-analysis. Ultrasound Obstet Gynecol 2013; 41:610.
- Bernhardt BA, Soucier D, Hanson K, et al. Women's experiences receiving abnormal prenatal chromosomal microarray testing results. Genet Med 2013; 15:139.
- Tyreman M, Abbott KM, Willatt LR, et al. High resolution array analysis: diagnosing pregnancies with abnormal ultrasound findings. J Med Genet 2009; 46:531.
- Committee Opinion No.682: Microarrays and Next-Generation Sequencing Technology: The Use of Advanced Genetic Diagnostic Tools in Obstetrics and Gynecology. Obstet Gynecol 2016; 128:e262.
- Xue Y, Ankala A, Wilcox WR, Hegde MR. Solving the molecular diagnostic testing conundrum for Mendelian disorders in the era of next-generation sequencing: single-gene, gene panel, or exome/genome sequencing. Genet Med 2015; 17:444.
- Krakow D, Lachman RS, Rimoin DL. Guidelines for the prenatal diagnosis of fetal skeletal dysplasias. Genet Med 2009; 11:127.
- Xue Y, Sun A, Mekikian PB, et al. FGFR3 mutation frequency in 324 cases from the International Skeletal Dysplasia Registry. Mol Genet Genomic Med 2014; 2:497.
- Croonen EA, Nillesen WM, Stuurman KE, et al. Prenatal diagnostic testing of the Noonan syndrome genes in fetuses with abnormal ultrasound findings. Eur J Hum Genet 2013; 21:936.
- Rabbani B, Tekin M, Mahdieh N. The promise of whole-exome sequencing in medical genetics. J Hum Genet 2014; 59:5.
- Farwell KD, Shahmirzadi L, El-Khechen D, et al. Enhanced utility of family-centered diagnostic exome sequencing with inheritance model-based analysis: results from 500 unselected families with undiagnosed genetic conditions. Genet Med 2015; 17:578.
- ACMG Board of Directors. Points to consider in the clinical application of genomic sequencing. Genet Med 2012; 14:759.
- Carss KJ, Hillman SC, Parthiban V, et al. Exome sequencing improves genetic diagnosis of structural fetal abnormalities revealed by ultrasound. Hum Mol Genet 2014; 23:3269.
- Drury S, Williams H, Trump N, et al. Exome sequencing for prenatal diagnosis of fetuses with sonographic abnormalities. Prenat Diagn 2015; 35:1010.
- Benn P, Cuckle H, Pergament E. Non-invasive prenatal testing for aneuploidy: current status and future prospects. Ultrasound Obstet Gynecol 2013; 42:15.
- Benachi A, Letourneau A, Kleinfinger P, et al. Cell-free DNA analysis in maternal plasma in cases of fetal abnormalities detected on ultrasound examination. Obstet Gynecol 2015; 125:1330.
- Oneda B, Steindl K, Masood R, et al. Noninvasive prenatal testing: more caution in counseling is needed in high risk pregnancies with ultrasound abnormalities. Eur J Obstet Gynecol Reprod Biol 2016; 200:72.
- Committee Opinion No. 640: Cell-Free DNA Screening For Fetal Aneuploidy. Obstet Gynecol 2015; 126:e31.
- Mennuti MT, Cherry AM, Morrissette JJ, Dugoff L. Is it time to sound an alarm about false-positive cell-free DNA testing for fetal aneuploidy? Am J Obstet Gynecol 2013; 209:415.
- Yaron Y, Jani J, Schmid M, Oepkes D. Current Status of Testing for Microdeletion Syndromes and Rare Autosomal Trisomies Using Cell-Free DNA Technology. Obstet Gynecol 2015; 126:1095.
- Yaron Y. The implications of non-invasive prenatal testing failures: a review of an under-discussed phenomenon. Prenat Diagn 2016; 36:391.
- Palomaki GE, Kloza EM, Lambert-Messerlian GM, et al. Circulating cell free DNA testing: are some test failures informative? Prenat Diagn 2015; 35:289.
- Breathnach FM, Fleming A, Malone FD. The second trimester genetic sonogram. Am J Med Genet C Semin Med Genet 2007; 145C:62.
- Shaffer LG, Rosenfeld JA, Dabell MP, et al. Detection rates of clinically significant genomic alterations by microarray analysis for specific anomalies detected by ultrasound. Prenat Diagn 2012; 32:986.
- Fonda Allen J, Stoll K, Bernhardt BA. Pre- and post-test genetic counseling for chromosomal and Mendelian disorders. Semin Perinatol 2016; 40:44.
- FREQUENCY OF CHROMOSOME ABNORMALITIES IN ANOMALOUS FETUSES
- DIAGNOSTIC TESTS
- Our approach
- Fluorescent in situ hybridization
- Karyotype and chromosomal microarray analysis
- Gene sequencing
- - Targeted gene sequencing
- - Whole exome sequencing
- SCREENING TESTS
- Our approach
- Cell-free DNA
- GENETIC EVALUATION OF THE FETUS WITH "SOFT MARKERS" AND NO STRUCTURAL ANOMALIES
- Pretest counseling
- Post-test counseling
- SUMMARY AND RECOMMENDATIONS