prenatal screening part i from embryo to 14 weeks · driven by early screening, early diagnosis,...

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Prenatal Screening Part Ifrom Embryo to 14 weeks

Ken Seethram, MD, FRCSC

Co-Director

Pacific Centre for Reproductive Medicine Clinics Vancouver, Edmonton

Clinical Associate Professor, Universities of British Columbia and Alberta

[email protected]

Faculty/Presenter Disclosure

Relationships with commercial interests:

Grants/Research Support:

Ferring Canada

EMD Serono

Merck Canada

Igenomix Global

Speakers Bureau/Honoraria/consulting fees: None

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Disclosure of Commercial Support

This program has not received financial support

This program has not received in-kind support

Potential for conflict(s) of interest: none

Mitigating Potential BiasAlthough research grants are received for other medical work, none of those grants apply to the content of prenatal screening

I am an accredited provider of the Fetal Medicine Foundation UK, for First trimester combined screening, which you will hear in this talk

Prenatal Screening - background

Prenatal screening is a very broad area of maternity care

Variations:Genetic screening

Anomaly screening

Twin screening

Hypertension/placental dysfunction screening

Prenatal genetic screening – has always been a key focus. It’s important, but keep in the front of your mind that we

are gradually moving towards screening that includes genetics, anomalies, and hypertension screening

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Prenatal Visits

24/28w

Shift in Care

Prenatal Visits

32/34/36w-43w1920

1TM 2TM 3TM

1970 Prenatal Visits 24/28w

Ultrasound 20w

Prenatal Visits

32/34/36-42w

1986-1996

Amniocentesis

CVS

Prenatal Visits 24/28w

Ultrasound 20w

Amniocentesis/CVS

16-20w TMS/QUAD

Amniocentesis/CVS

16-20w TMS/QUAD

First Trimester Screening (FTS)

1992-2011

Prenatal Visits

32/34/36-42w

Prenatal Visits 24/28w

Ultrasound 20w

2011-2020

Prenatal Visits

32/34/36-41w

Amniocentesis/CVS

16-20w TMS/QUAD

FTS and NIPT

Prenatal screening – the shift

We have seen an enormous shift from 2TM and 3TM focus, into First Trimester Screening focus

Driven by early screening, early diagnosis, early management

Risk reduction strategies and better care in the 2nd and 3rd trimesters with increased 1st trimester knowledge

Downside: shift has pushed essential elements of prenatal care into the realm of providers who may not be doing prenatal care

Therefore, the primary maternity care provider (Family Physician, Midwife, and Obstetrician) is fundamental to

successful outcomes by providing the right early prenatal screening.

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Prenatal Screening - outline

Prenatal genetic screening – what?What are we screening for?

Who do we screen?

Prenatal Genetic screening – how?1. Pre-implantation Genetics

2. First trimester screening

3. NIPT

4. SIPS/IPS

5. Combined/Contingency screening

Pearls

What are we screening for?

The big things: aneuploidyMajor chromosome number deviations such as Trisomy's 21/18/13 (T21/18/13) and monosomy X (45X)

Increased incidence with age

The little things: subchromosomalDeletions/duplications of chromosomal segments

Single gene disorders

Chorionicity in twins

These are independent of age

Prenatal Screening

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AneuploidyGeneral population prevalence is for Trisomy 21: ~1/700 in Canada

T21 and 45X are the only two common aneuploidy conditions which are compatible with life

Other sex chromosome aneuploidy like XXY/XXX/XYY are generally low impact on health outcomes

Population prevalence estimates put T21 at 8.3/10000 (31,100) in Canada

It is a continuum from conceptus onwards - How common is it embryonic stage?

Current estimates say that 60% of all embryos in a woman aged 40 will have aneuploidy

What is the chance of a pregnancy being normal at a given age?.....

Prenatal Screening - aneuploidy

Risk of Down syndrome at 10w by maternal age

Age Chance of T21 Chance of normal

30 1:576 99.82%

35 1:229 99.56%

40 1:62 98.39%

42 1:35 97.14%

45 1:15 93.33%


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So in the advanced maternal age patient (aged 35-45) the chance of a normal outcome will range from 93-99%

The primary message here - pregnancy is a normal conditionthe vast majority of times, even as a woman ages beyond 40, the outcomes are excellent

Despite that - why has prenatal screening become so prevalent?

New technology gives more accuracy - (First Trimester screening, Non Invasive prenatal testing)

Google (the great physician, the best doctor ever)

Increased patient knowledge and possibly anxiety

The marketing machine of big genome



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Now what about the little things?

Deletions/duplications of chromosomal segments

Single gene disorders

Chorionicity in twins

These are all outcomes from non-invasive prenatal testing (NIPT) and they are all exceptionally rare

Examples of deletions: 22q11.2, Prader Willi, Angelman’s, 1p36 etc.

<1:5000-1:10000 newborns

Note that although rare, they are not age-related

Prenatal Screening - subchromosomal

The Big Thing:

Aneuploidy

The Little Things:

Deletion/duplications

Single Gene disorders

Quick Summary

SCREENING

Increasing prevalence

with increasing age

Not age related

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Who do we screen?

So we know what we’re screening for

But WHO do we screen?

What we used to do – just screen patients over age 35

Who do we screen?

What we do now is super simple….

• SOGC, ACOG, ISPD, CCMG

• Why? A pregnant patient doesn’t care about the risk of her peers, she only cares about her risk.

• Keep in mind that provincial resources determine what is offered – but it is necessary to counsel women about what is offered and what is available

Every pregnant woman, regardless of age, and after an

informed consent process, should be offered prenatal

genetic screening for the most common aneuploidies

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The Little Things:

Deletion/duplications

Single Gene disorders

Quick Summary

The Big Thing:

Aneuploidy

Everyone

Why Who How

That’s what we’re

going to talk about

now

Prenatal genetic screening – HOW?

First Trimester Screening

Serum Integrated Prenatal Screening

Integrated Prenatal Screening

Non invasive prenatal testing (NIPT)

Combinations/contingency models

Pre-Implantation Genetic Testing – PGT

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rapidly increasing as part of IVF treatment

trophectoderm biopsy, Next Gen Sequencing

Older terms were PGD, PGS, Comprehensive chromosome screening (CCS), but the new global terms are;

Preimplantation genetic testing (PGT)

For Monogenic disorders (PGT-M)

For Aneuploidy (PGT-A)

For Chromosomal Structural Rearrangements (PGT-SR)

Proving very useful for embryo selection, and for management of complex genetic conditions

Prenatal genetic screening – what tools do we have?

Pre-Implantation Genetic Testing – PGT

Due to false positive and false

negative risks, these patients still

require prenatal genetic screening –

although their a priori risks are

lower than age based







Pre-Implantation Genetic Testing – PGT ✓

All of these tools use either the fetus or the placenta to give us information

FTS

SIPS

IPS

NIPT

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PlacentaWe get information of biochemical markers which move up or down in different genetic syndromes

These can be done in the first trimester (1TM) or second trimester (2TM) or both

Includes: HCG, PAPP-A, Inhibin-A, estriol, Alpha fetoprotein (AFP)

The HCG we measure in the 1TM is different than 2TM, but they give the same info

We can also get DNA fragments which we can compile to genome the baby (NIPT)

FetalUltrasound in the first or second trimester – global drift towards first trimester

Nuchal Translucency

Nasal bone

ductus venosus flow

anatomy survey in 1TM and 2TM

soft genetic markers in the 2TM


How can we use placental serum markers, and ultrasound markers in combination?

• This is how we derived combined prenatal screening

• QUAD, SIPS, IPS, FTS

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HCG

AFP

uE3

Inhibin-A

15-22W blood11-14W blood

QUADRUPLE PREGNANCY SCREEN75%

11-14W US


HCG

AFP

uE3

Inhibin-A


PAPP-A

SERUM INTEGRATED PREGNANCY SCREEN80-82%

11-14W US

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HCG

AFP

uE3

Inhibin-A

15-22W blood11-14W blood11-14W US

PAPP-ANuchal Translucency

INTEGRATED PREGNANCY SCREEN84-88%


HCG

AFP

uE3

Inhibin-A



FIRST TRIMESTER PREGNANCY SCREEN

HCG

85%

11-14W US

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11-14W blood


FIRST TRIMESTER PREGNANCY SCREEN

HCGNasal Bone

Ductus Venosus

96%

11-14W US


So to summarize: you can use placental proteins, early or late, and ultrasound (early)

Timing for results:

FTS provides results at

11-14w

QUAD/SIPS/IPS all provide

results at 16-22w

Timing will impact decision making if

abnormal results require more testing

or termination

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Prenatal genetic screening – what tools do we have?







✓

✓

✓

Prenatal genetic screening – NIPT and the genome

Non-invasive Prenatal Testing (NIPT)DNA is liberated from the developing placenta and can be fractioned away from maternal circulating DNA

This “cell-free” DNA is placental, not fetal, but fully represents the fetus

The fragments are 150 base pairs long, and the genome is 3B base pairs, but the entire fetal genome is represented in these fragments

By counting technologies, Array sequencing, or Next Gen Sequencing the genome of the fetus can be reconstructed to detect:

Aneuploidy

Microdeletions

Some single gene mutations

Placentation in twins

Don’t try to hard to understand the mathematics – whether you count genomic segments, or sequence them, the results are extremely accurate

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Non-invasive Prenatal Testing (NIPT) – performance?Aneuploidy

Performance for T21 is over 99% detection rates for 0.1% false positive rates

Tells us about the placental DNA but not the baby

Performance for T13/T18/Sex chromosomes less well but still high (about 90%)

What about microdeletions

SNP sequencing is the only NIPT which can look for small deletions in the chromosomes

Syndromes from microdeletions can be quite severe

What about Twins

Sequencing with Single nucleotide polymorphisms (SNPs) provides one thing: zygosity (if in doubt)


Free DNA comes from

apoptotic cells derived from:

• Maternal Circulation

• Adipocytes

• White Blood Cells

• “Fetal”

• Placental cells (trophoblasts) in

the maternal circulation

• Fetal Fraction – the percent ratio

between placental: maternal DNA

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You may have heard of fetal fraction?

Low FF seen in: Early gestation, high BMI, collection issues, aneuploidy

This can drop the accuracy of results

Minimum required: 4% for counting, 2.8% for SNP

If fetal fraction is low….

Redraw

Option of other screening methods

Up to 30% of people on redraw will still get non-reporting

So although it’s a great test, 3-5% of all patients will get non-reporting


NIPT - microdeletions?

DiGeorge syndrome 22q11.2 deletion risk: 1:2000-4000

Risk of dying in a car: 1:5000

Risk of dying in pregnancy in Canada: 1:8800

Risk of having a child with autism/spectrum: 1:68

What’s my point?

Microdeletion syndromes are rare

People read about these on the google and on the twitter, and they displace their baby concern with the concern for truly rare diseases

For the most part, don’t specifically order NIPT for microdeletion or single gene unless you have an at-risk patient. Array CGH platforms for NIPT can help with

Chorionicity

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What are the major NIPTs available?

Targeted (counting method) – example - Harmony©

Where we look for gene loci unique to certain chromosomes (like 21) and compare that number with the reads from other chromosomes (like 1)

If you get more reads from the locus on 21 in a ratio of 1.5X versus 1, then you have trisomy 21

SNP based – example - Panorama©

Where DNA sequence variations (normal in all of us) are compared between placental and maternal DNA

Variations of up to 1% are normal

This can then help segregate and compare maternal versus placental DNA

Benefits – microdeletions, zygosity, slightly lower fetal fraction threshold

Whole Genome sequencing – example NIFTYpro©

All chromosome numeric abnormalities

84 microdeletions

March 2018

Prenatal genetic screening – NIPT alone?

NIPT difficult situations?

Fetal demise in a twin pregnancy

Donor egg – yes

Donor sperm – yes

The big limitation of blood based screening (SIPS or NIPT):

Is that we don’t see the baby

In fact all screening tools which do not use ultrasound will miss up to 40% of abnormal pregnancies

NIPT in particular - High cost for detecting of T21

Misses up to 10% of atypical chromosomal’s like triploidy, and Non T21/18/13

3-5% risk of non reporting

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Prenatal genetic screening – NIPT alone?

Why not do NIPT alone?Ex. Ductus venosus screening will detect 93-96% of all cardiac anomalies at 11-14w

Kenkhuis March 2018 – 100% of severe structural anomalies will be picked up at the 11-14w scan

Abuhamad 2017 – 100% DR for acrania, omphalocele, gastroschisis, megacystis, body stalk anomaly, cloacal defect, amongst others

It’s important to understand that NIPT is really good at T21, but not great at other things – it catches the 60% of genomic anomalies, but at the cost of missing 40%

Hence our National Guidelines….

These guidelines are joint between Society of OBGYNs of Canada (SOGC) and Canadian College of Medical Geneticists (CCMG)

They also reflect the opinions of

• International Society of Prenatal Diagnosis (ISPD)

• American College of OBGYNs (ACOG)

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Guidelines - What you need to know:

A. First Trimester Ultrasound (11-14w) offers many advantages including dating, Chorionicity, early detection of major structural abnormalities, and aneuploidy risk

B. Second Trimester AFP is no longer required if a 20w ultrasound is done

C. In twin pregnancies, Nuchal Translucency alone is considered an acceptable first line test, better with serum proteins like HCG/PAPP-A

D. NIPT is a highly effective form of early prenatal screening of common trisomy's after 10w. NIPT as a primary screening is not cost effective, but offering it in a contingency program will give high performance at a reduced cost


Guidelines - What is actually happening

A. Due to direct to consumer marketing, NIPT is replacing screening

B. We are ignoring the benefits of early US for detection of genetics and structural anomalies

C. Due to big genomics, the costs of screening are being outsourced to the patient, instead of system pressures to improve the provision of prenatal care

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The future of Prenatal Screening

Future of Prenatal Screening

First Trimester

Screening

Multiple markers

NIPT (1TM) Genomic information

Second

Trimester

Ultrasound and medical screening

By 20w to triage those at very low risk, and those at high risk –

concentrating prenatal care on those who need it:

anomalies, PIH risk, Preterm birth risk, etc








✓

✓

✓

✓

✓

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What do I offer patients today?

Wants to screen but

within insured

services

Wants to screen but

willing to pay and

wants better

performance

Wants to screen,

willing to pay, and

wants as much

information as

possible

Under 35

Over 35/twins/IVF-ICSI

SIPS

IPS (NT plus SIPS)


(NT, NB, DV, serum HCG

and PAPP-A)

Any age, per national

guidelines


with NIPT

What do I offer patients today?

Is there an

insured NIPT in

BC?

If any screening test

is abnormal, the

patient can choose to

do NIPT or

Amniocentesis/CVS

Previous

T21/T13/T18

pregnancy

This type of

contingency

model is very

efficient and

cost-effective

20w soft markers

increasing risk above

1:300

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PEARLS

Offer all forms of screening to all women regardless of their age based risk

Invasive testing follows if the screening test is positive

Conventional screening methods remain the most appropriate choice for first-line screening, with NIPT contingency

Patients who did IVF with PGT still require prenatal genetic screening

All of the genetic risks we seek to screen are rare – provide reassurance

New technology such as NIPT – don’t apply it alone – it is an excellent augmentation to conventional screening, but isn’t as broad as any screening which includes ultrasound

PEARLS

Recognize that some of the single gene and microdeletion panels are extremely rare and not a sole reason for doing NIPT

Don’t forget that the embryo can also be tested (PGT)– growing science

Work within what your patients want – 50% of all pregnant patients in this province decline any type of screening.

Educate them, let them know what is available, and help them reach a decision

Remember, all women, regardless of age, should have an informed choice about prenatal screening options

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Pearls

If you get lost and don’t know what to do?

[email protected] – you or your patient can email our counselors, or call us to assist

My talk – at pacificfertility.ca >top of the page – physician resources

Email me – [email protected]

Perinatal BC Prenatal Genetic screening website has a video and decision aides

How to order SIPS

Go to this link http://www.perinatalservicesbc.ca/Documents/Screening/Prenatal-HCP/PrenatalBiochemistryLabReq.pdf

Fill it out and the patient goes to the lab for the blood draw

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How to order IPS

Do the same requisition http://www.perinatalservicesbc.ca/Documents/Screening/Prenatal-HCP/PrenatalBiochemistryLabReq.pdf

You also have to do the Nuchal translucency requisition:

Found here: http://www.perinatalservicesbc.ca/Documents/Screening/Prenatal-HCP/NTSites.pdf - do up an ultrasound requisition and send patient for this ultrasound at 11-14 weeks

How to order NIPT

Go to this link: http://www.perinatalservicesbc.ca/Documents/Screening/Prenatal-HCP/DynacareLabRequisition_Funded.pdf

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How to order non-insured NIPT

Go to this link: https://www.lifelabsgenetics.com/product/non-invasive-prenatal-testing/

other providers:

Dynecare

PCRM

Olive Fertility

How to order First Trimester Screening

Go to this link: https://pacificfertility.ca/service-types/prenatal-screening

have patient speak with our genetic counselors about FTS/NIPT/Insured or non-insured prenatal screening