Further multimarker Down syndrome strategies Ultrasound screening for OSB Other Down syndrome markers Clinical factors Edwards syndrome (trisomy 18) Other conditions associated with altered markers Planning a program Conclusion Acknowledgments References
14 7 Noninvasive Screening for Aneuploidy Using Cell‐Free Placental DNA Introduction Cell‐free DNA Performance of cell‐free DNA screening Sex chromosome aneuploidy Cell‐free DNA screening approaches Cell‐free DNA test failures False‐positive cell‐free DNA results and incidental findings False‐negative cell‐free DNA results Cell‐free DNA screening for microdeletion syndromes Genome‐wide cell‐free DNA screening Pretest counseling Post‐test screening Comparison of cell‐free DNA screening to traditional screening Use of prenatal ultrasound in the setting of cell‐free DNA Multiple gestations Cell‐based noninvasive prenatal testing Conclusion References
15 8 Noninvasive Prenatal Diagnosis and Screening for Monogenic Disorders Using Cell‐Free DNA Introduction Biology and characteristics of cell‐free DNA in maternal blood General approaches for testing of single‐gene disorders by fetal cell‐free DNA analysis Current status of noninvasive single‐gene testing by cell‐free DNA analysis Noninvasive prenatal diagnosis of monogenic disorders Noninvasive prenatal screening using panels of single‐gene disorders by cell‐free DNA analysis Clinical implementation: ethical and social issues Summary and future directions References
16 9 Amniocentesis, Chorionic Villus Sampling, and Fetal Blood Sampling Introduction Amniocentesis Chorionic villus sampling Fetal blood sampling Cardiocentesis References
17 10 Prenatal Diagnosis of Neural Tube Defects Biology of α‐fetoprotein Amniotic fluid α‐fetoprotein Amniotic fluid acetylcholinesterase Recommendations for prenatal diagnosis of NTDs using AFAFP and AChE assays Other techniques to detect neural tube defects Primary prevention of neural tube defects Complications and life expectancy References Additional references
18 11 Prenatal Diagnosis of Chromosomal Abnormalities through Chorionic Villus Sampling and Amniocentesis The incidence of chromosomal abnormalities detected by conventional cytogenetics Indications for prenatal cytogenetic diagnosis Interpretation issues: chromosome mosaicism and pseudomosaicism Interpretation issues: chromosome rearrangements Interpretation issues: chromosome polymorphisms, common inversions, and other structural variations Interpretation issues: maternal cell contamination Factors affecting diagnostic success rate and accuracy Technical standards for prenatal cytogenetics laboratories Error rates in prenatal cytogenetic diagnosis Discordance between karyotyping and molecular genetic testing Conclusion Acknowledgments