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  • Prenatal screening and diagnosis of chromosomal and genetic conditions in the fetus in pregnancy

    Objectives: This statement is intended to provide advice on the recommended screening and diagnostic tests for chromosomal and other genetic conditionsin the fetus. Outcomes: Improved access to effective screening and diagnostic tests for chromosomal and genetic conditions.

    Target audience: This statement is intended for use by health professionals providing antenatal care including:

    • Clinicians: doctors (obstetricians, clinical geneticists, radiologists and general practitioners), midwives, nurses and genetic counsellors;

    • Scientists, laboratory staff and administrative staff delivering services for prenatal screening and diagnosis.

    Other audiences: This statement provides useful information for patients and carers, researchers, health policy makers, health regulators and those responsible for quality and safety of healthcare. This statement may also be a valuable resource to State and Federal Government bodies developing guidelines and other documents on prenatal screening and diagnosis. Values: The evidence was reviewed by the HGSA/RANZCOG Joint Committee on Prenatal Diagnosis and Screening, and applied to local factors relating to Australia and New Zealand.

    Background: This statement was first developed by the HGSA/RANZCOG Joint Committee on Prenatal Diagnosis and Screening (Prenatal Screening Tests for Trisomy 21, Trisomy 18 and Neural Tube Defects -C-Obs 4 in 1991 and Prenatal diagnosis policy - C- Obs 5 in 1990). In 2014-15, C-Obs 4 and C-Obs 5 were significantly edited by the committee to create this current version (C-Obs 59).

    This statement has been developed and reviewed by the HGSA/RANZCOG Joint Committee on Prenatal Diagnosis and Screening and approved by the Women’s Health Committee and RANZCOG Council. Dr Lisa Hui was the guest author of Appendix D on cell free fetal DNA screening.

    A list of members of the HGSA/RANZCOG Joint Committee on Prenatal Diagnosis and Screening can be found in Appendix A and Women’s Health Committee in Appendix B.

    The committee acknowledges the contribution of Dr George McGillivray, Dr Lisa Hui and Professor Jane Halliday to this document.

    Disclosure statements have been received from all members of this committee and contributors.

    Disclaimer This information is intended to provide general advice to practitioners. This information should not be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of any patient. This document reflects emerging clinical and scientific advances as of the date issued and is subject to change. The document has been prepared having regard to general circumstances. Funding: The development and review of this statement was funded by RANZCOG.

    First endorsed by RANZCOG: March 2015 Current: March 2015, Amended May 2016 Review due: March 2016 or as required

    The Royal Australian and New Zealand College of Obstetricians and Gynaecologists

  • Prenatal screening and diagnosis of chromosomal and genetic abnormalities in the fetus in pregnancy

    C-Obs 59 Page | 2

    Table of contents

    1. Patient summary ....................................................................................................................... 4

    2. Summary of recommendations ................................................................................................... 5

    3. Discussion and recommendations............................................................................................... 7

    3.1 Prenatal tests for aneuploidy .................................................................................................... 7

    3.2 Prenatal screening tests for fetal aneuploidy .............................................................................. 8

    3.2.1 Additional first trimester markers of aneuploidy ............................................................. 10

    3.2.2 Confounding maternal factors ..................................................................................... 10

    3.2.3 Cell free DNA-based screening for fetal aneuploidy ....................................................... 10

    3.2.4 Screening for aneuploidy in multiple pregnancies .......................................................... 12

    3.3 Prenatal diagnostic procedures for suspected chromosome or genetic conditions ...................... 13

    3.3.1 Amniocentesis ............................................................................................................ 13

    3.3.2 Chorionic villus sampling (CVS) ................................................................................... 13

    3.4 Assessment of fetal chromosomes following CVS or amniocentesis ........................................... 13

    3.5 Prenatal tests for other genetic disorders ................................................................................. 14

    3.5.1 Population-based periconceptional genetic screening .................................................... 14

    3.5.2 Prenatal diagnosis for genetic disorders on the basis of a family history of a known or suspected genetic disorder ....................................................................................................... 15

    3.5.3 Prenatal screening for genetic disorders suspected on the basis of fetal condition ............ 15

    3.6 Prenatal screening by fetal ultrasound in mid-trimester ............................................................. 16

    3.7 Other issues ......................................................................................................................... 16

    3.7.1 Assisted reproductive technologies (ART) ....................................................................... 16

    3.7.2 Pre-implantation genetic diagnosis (PGD) ..................................................................... 16

    4. Governance ........................................................................................................................... 17

    4.1 Quality Assurance ................................................................................................................ 17

    4.1.1 Education for health professionals involved in prenatal screening ....................................... 17

    4.1.2 Performance quality standards and monitoring processes .................................................. 17

    i) Laboratory accreditation ....................................................................................................... 17

    ii) Sonographer accreditation ................................................................................................... 17

    iii) Internal and external performance audit ............................................................................... 18

    5. References .............................................................................................................................. 19

    6. Other suggested reading ......................................................................................................... 22

    7. Links to other College statements ............................................................................................. 22

    8. Patient information .................................................................................................................. 22

  • Prenatal screening and diagnosis of chromosomal and genetic abnormalities in the fetus in pregnancy

    C-Obs 59 Page | 3

    Appendices ................................................................................................................................... 23

    Appendix A ................................................................................................................................ 23

    Human Genetics Society of Australia (HGSA) and the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) Joint Committee on Prenatal Diagnosis and Screening Membership ............................................................................................................................... 23

    Appendix B Women’s Health Committee Membership ................................................................... 24

    Appendix C Overview of the Development and Review Process for this Statement ............................. 24

    Appendix D Full Disclaimer ......................................................................................................... 26

    Appendix E Cell-free DNA Testing for Fetal Aneuploidy .................................................................. 27

    Appendix F Considerations for Indigenous and Culturally and Linguistically Diverse Populations ........ 33

    Appendix G Disorders Based on Ethnicity...................................................................................... 34

    Appendix H Definitions and Abbreviations .................................................................................... 35

  • Prenatal screening and diagnosis of chromosomal and genetic abnormalities in the fetus in pregnancy

    C-Obs 59 Page | 4

    1. Patient summary Every baby has a small chance of having a chromosomal or genetic condition.∗ Prenatal screening for some chromosomal and genetic conditions is offered in maternity care to p

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