Pregnancy Tests Explained (2Nd Edition): Current Trends of Antenatal Tests

By Dr Patrick Chia FRCOG FAFP (Mal) and Dr Vijayan V FRCOG

Antenatal diagnosis has come a long way. As newer, more accurate, and less-invasive screening tests are available, doctors must constantly update themselves via the most recent research and publications.
Good antenatal care is essential. Over the last decade we have seen rapid advances in medical technology that allowed the development of tools and tests essential to help reduce the risks to the mother and her developing foetus. The high-resolution transvaginal probe, with its crystal-clear view of the foetus, now make it possible for first-trimester diagnoses. From the perspective of the doctor, these tests will provide vital information that will be utilised to optimise antenatal care. It will afford early and timely intervention in terms of in utero therapy or prepare the mother for a potentially unfavourable outcome.
Owing to the introduction of newer testing techniques, we have seen a shift in screening strategies. It has broadened the scope of antenatal testing from increasingly higher resolution ultrasound scans to genome molecular tests. In addition, non-invasive prenatal diagnoses are increasingly available and becoming more affordable.

• Language: English
• Publisher: Partridge Publishing Singapore
• Release date: Jan 29, 2023
• ISBN: 9781543771282

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ISBN

ISBN: 978-1-5437-7127-5 (sc)

ISBN: 978-1-5437-7129-9 (hc)

ISBN: 978-1-5437-7128-2 (e)

Library of Congress Control Number: 2022915610

01/27/2023

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PREGNANCY TESTS EXPLAINED

(SECOND EDITION)

UNDERSTANDING THE NEWER TRENDS

This book is

dedicated to

Dr James (Jim) Alcock, FRCGP, MBE

Contents

Preface

Introduction

1     Antenatal Tests

2     What Makes a Good Test?

3     Normal Physiological Changes in Pregnancy

4     Testing the Mother

5     Testing the Foetus

6     The Non-Invasive Prenatal Test (NIPT)

7     Invasive Diagnostic Tests

8     Laboratory Tests

9     The Newer Trends in Laboratory Testing

10   Ultrasound Scan in Obstetrics

11   The Detection of Foetal Anomalies Using 3D/4D Ultrasound

12   To Test or Not to Test? That Is the Question

13   Reshaping Maternal and Perinatal Care

APPENDIX (A)

APPENDIX (B)

APPENDIX (C)

APPENDIX (D)

Preface

It has been about a decade since the publication of the first edition of Pregnancy Tests Explained. Within this timeframe there had been extensive medical advances, making the process of having a child much safer for the mother and her baby.

From the image perspective, advances in the supercomputer technology has improved so much that the startling imagery of the first trimester foetus continues to mesmerise us. These game-changing machines have pushed the frontiers of prenatal diagnosis into the first trimester, making it commonplace to detect up to 50 per cent of major foetal anomalies.

Good antenatal care will always result in a reduction in maternal deaths, making the process of labour and delivery a much safer one for the mother. The recent test utilizes maternal serum PlGF (placental growth factor) in combination with PAPP-A (pregnancy-associated plasma protein A). The measurement is combined with the uterine artery doppler velocimetry and can detect 80 per cent of preeclampsia. Taking aspirin in this group of patients will reduce the occurrence, and possibly the severity of disease, by 60 per cent.

Other challenges include inherent difficulties of interpreting the results of the advanced invasive prenatal testing, such as the WES (whole exome sequencing) test. It is notoriously difficult to interpret the results. Furthermore, it takes too long to process samples and is often too costly for parents. However, with further improvements in bioinformatics and the use of a newer, next-generation sequencer (NGS), the interrogation is much more thorough and faster. As our experience increases, our understanding of such tests will also improve. WES is now increasingly being utilized in the assessment of the foetus with structural anomalies in prenatal setting.

The other improvement is the use of 3D/4D ultrasonography in the assessment of the foetus in utero. The ability to generate crystal-clear images continues to mesmerize us. The MRI may be superior in confirming structural foetal malformations, but its value is highly dependent on the person who views the images. STIC (spatio, temporal, image correlation) technology has contributed much to the assessment of the fetal heart and its vessels.

Maternal biochemistry continues to play a significant role in the assessment of maternal, foetal, and placental health. As their value changes due to the adaptive changes throughout pregnancy, it is essential to alter the correct value for that gestational age to enable correct interpretation.

Introduction

Medical data are health related and therefore prone towards bias with claims of better treatments and cures. We have learned much from the coronavirus pandemic, which has crippled the world for several years. The vast expanse of data had to undergo robust scrutiny to check on their validity and reliability of tests or treatment of COVID-19. Using a common medical search engine, PubMed, a search for COVID-19 therapy yielded more than five million articles. A good paper will change the way we practise. But the result of such research is not beyond reproach, and it will not be influenced by the plethora of information presented.

The same questions remain:

• How do we discern the good tests from the bad ones?

• Are they evidence-based?

• Are there clear benefits?

• Will it harm?

• Is the study/test reproducible? If so, from which institution?

• Is it cost effective?

A dearth of medical information is available seamlessly for free to explore and is obtained from the worldwide web. We have seen how misinformation and misuse of good information have led countless astray, which forms the basis of so-called fake news. This book dissects common tests used during pregnancy and presents them in logical fashion.

This second edition of Pregnancy Tests Explained is a testament to critical analysis of information published about pregnancy tests. It has been updated extensively regarding minimal standards on screening of both mother and foetus. The publication of this second edition is also a testament to the success of the first.

The rapid adoption of the NIPT (non-invasive prenatal test) as a reliable test for the screening of Down syndrome carries ethical and moral issues that should be addressed alongside its value as a good screening test for Down syndrome.

NIPT made its debut in 2012 as the test of the century. It has changed the face of antenatal care. The use of advanced genetic tests certainly increases opportunities for genomics and gene therapy. We are sure the public and members of the healthcare profession will find this book not only an enlightening read but a useful reference manual.

Current Trends in Antenatal Testing

Antenatal care aims to safeguard the health and well-being of the mother and foetus during pregnancy. They are important tools that help doctors identify potential problems in the early stages of pregnancy, which, if not addressed or treated, may result in increased risks for the mother and her developing foetus. Some tests are done routinely while others are offered only to certain women because of their ages and medical or family histories. Other tests are done only when an abnormality is found during a pregnancy exam.

As with any test or procedure, antenatal testing and screening should not be undertaken without informed consent of the woman after adequate and appropriate counselling about the implications, limitations, and consequences of each test or investigation.

Mothers-to-be are routinely offered numerous tests, which are often taken without prior explanation or discussion, and there is little understanding of what the tests are for or what happens when a test is positive. Consequently, parents-to-be are often left bewildered, confused, and unnecessarily anxious about their pregnancies.

Even some healthcare professionals get it wrong. They appear to misunderstand some pregnancy tests. The objective of this book is to inform parents about the tests that are offered so they understand what is available. It is intended to help parents make informed decisions about their pregnancies.

1

Antenatal Tests

Antenatal tests (Figure 1.1) involves both screening and diagnostic tests. The screening tests, being non-invasive, do not jeopardize or pose any risk to the pregnancy. They do not cause a miscarriage. However, their sensitivity is not 100 per cent, which means the detection rate is not 100 percent. In this context, screening tests for Down syndrome do not completely detect or exclude the condition. Examples of screening tests for Down syndrome include ultrasound scans and the triple test.

In 2012, the NIPT (noninvasive prenatal test) emerged, giving pregnant women a screening test that can detect almost 100 per cent of Down syndrome. This prenatal test can be done at eight