PRE-PREGNANCY & FIRST TRIMESTER TESTS

Dr Samantha Hargreaves

PRE PREGNANCY COUNSELLING

• Hospitals/models of care

• Insurance

• Periconceptual folate

• Iodine

• Dietary advice/ weight management

• Exercise, alcohol, drugs

• vaccinations

PRE PREGNANCY COUNSELLING

• Viral serology – rubella, varicella

(+/- CMV)

• Vit D, Fe

• B12 if vegetarian

• Cytology +/- STI screen

• VCGS genetic carrier screening

VCGS Reproductive screen

• CF

• SMA

• Fragile X

These disorders are

• Common

• Severe

• Tests relatively sensitive and specific

• Mature technology

Research supports screening

Partnership with support organisations

Cost to patient AU$385

VCGS reproductive genetic carrier screen

RGCS - key points

Carrier testing for: Detection rates:

• Cystic fibrosis CF: 90% (38 gene changes)

• Spinal muscular atrophy SMA: 95%

• Fragile X FXS: >99%

• It is recommended that the female member of the couple is screened first as FXS testing is not necessary for the male partner.

• We recommend having screening either prior to pregnancy or before 12 weeks of pregnancy for pregnant patients.

• If there is a family history, please provide as much detail as possible.

• A blood sample is required.

• Results are available in approximately 10 working days.

• Cost is $385 or $325 for two of the three conditions. If partner testing is required, the charge is $220 for SMA and $150 for CF.

If no gene change is found, could I still be a carrier? • YES. The current carrier test detects the majority of carriers but it cannot detect

every gene change that causes CF, FXS and SMA.

• If no gene change is found, you are not a carrier of the most common gene

changes, but there is still a small risk for each condition that you are a carrier of

rarer gene changes.

Is genetic counselling available ? • YES. Genetic counselling is available throughout the process. Genetic

counsellors can disclose and discuss results, arrange partner testing and discuss family cascade testing.

• If a carrier couple is identified, couples are offered support, the opportunity to discuss reproductive options and meet with a physician specialising in the relevant condition.

FIRST TRIMESTER TESTS

• Blood group & antibody

screen

• FBE/diff

• Rubella, HEP B,C, HIV, Syphilis

• CMV, Toxo, Parvovirus,

Varicella

• MSU

• Vit D

• TFTs

FIRST TRIMESTER SCREENING for

ANEUPLOIDY

Non-invasive prenatal testing (NIPT) What is it?

Where does it fit in the pre-natal testing pathway?

Origin of cell free DNA Approx 10% of cfDNA in maternal plasma is fetal Fetal fraction ↑ gestation ↓ weight (BMI) Isolate maternal plasma, extract cfDNA, create libraries for sequencing maternal and fetal cf DNA Align sequence reads and determine number of reads relative to normal reference (molecular counting)

T21 sensitivity >99% T21 specificity =99.9%

cfDNA prenatal testing process (perceptTM)

• Plasma isolated from blood

• cfDNA extraction (maternal and fetal), sequence library prep and MPS

• Sequence tags (36 bp) are aligned to the reference genome

• Each unique tag is counted, total counts compared to reference

• av. 22.0 M tags per patient (multiplexed – 15 patients per run = 330M)

• Results expressed as

Z-score or NCV

• Z-score = stdev from mean

>4.0 99.994

Why 10 weeks and why a scan

Fetal fraction

• Fetal fraction (ff) is dependant on gestational

age

• As ff decreases (<4%), the risk of a false

negative increases

• 10 weeks gestation cut off

• Scanning is a more accurate calculation of

gestation

• Other factors can influence ff include.

• Maternal BMI

• Twin + pregnancies

• Non invasive

• Blood sample from mother contains maternal and fetal DNA – circulating cell-free fetal DNA (cfDNA) (average 10%)

• From 10 weeks gestation as determined by dating ultrasound

• Identify if the fetus is at high risk for having extra or missing copies of chromosome 21,18,13, X or Y

• Results available 3-5 days after sample received by VCGS (Melbourne)

laboratory

• $489.00 for test

VCGS percePT™ Test Characteristics

Results A Low risk:

• The test has identified a very low chance for the fetus to have an extra or missing copy(s) of one (or more) of chromosomes 21,18,13, X and Y

A High risk:

• the test has identified a very high chance for the fetus to have an extra or missing copy (s) of one (or more) of chromosomes 21,18,13,X and Y

It is recommended that high risk results are confirmed with a diagnostic test (i.e) CVS or Amniocentesis

(small chance of false positive)

Limitations

• Specific screen for T21, T18, T13, SCA : samples are analysed for whole chromosome abnormalities of chromosomes 21,18,13 and X and Y only

• NIPT cannot detect other chromosomal abnormalities

• NIPT is a screening test – it is not a replacement for invasive prenatal diagnostic tests (CVS, amniocentesis)

NIPT process

• Pregnancy dates confirmed via ultrasound

• Discussion with patient and information brochure provided

• Request form completed (including consent)

• Blood collection from 10 weeks gestation onwards

• Specific collection centres see: www.vcgs.org.au

• Sample processed by VCGS in Melbourne

• Test turn around time: 3-5 working days from receipt of sample

• Results communicated to referring health professional by VCGS

• Comprehensive service: VCGS genetic counsellors available to discuss testing and results at any point throughout the process

RANZCOG: College Communique (April 2015):

“NIPT is an option for those women who are able to self-fund their testing, after appropriate pre-test genetic counselling…”

“Prenatal screening tests are best implemented in the context of a therapeutic relationship and a program that co-ordinates pre-test counselling, testing, post-test interpretation, support during decision-making, and where indicated, follow-up consultations and diagnostic testing.”

“All women with an abnormal result on NIPT should have genetic counselling and be offered invasive testing for the confirmation of the diagnosis.”

Currently no clear consensus in Australia for the most appropriate approach for incorporation of NIPT into the prenatal screening pathway

Position Statement

NIPT for: • Singleton and twin pregnancies

• Any age or ethnicity

• IVF pregnancies

• At least 10 weeks gestation

Women at high risk for aneuploidy due to:

• Advanced Maternal Age (AMA)

• An increased risk on Maternal Serum Screening: 1in 50-1 in 1,000

• Personal or family history of aneuploidy

NIPT not for:

• Higher order multiple pregnancies

• Presence of ultrasound abnormality

• Increased nuchal translucency measurement (≥3.5mm)

• Very high maternal serum screening risk (≥ 1in 50)

Combined First Trimester Screening (cFTS)

RANZCOG (April, 2015): “…combined first trimester screening with nuchal translucency

measurement and serum markers remains an acceptable standard of care in high risk or

average risk women”

• Considered the “Gold standard” prenatal screening test

• Screens for Down syndrome (Trisomy 21), Trisomy 18 & Trisomy 13

• Risk calculation combines:

*Serum Biochemistry- Free-hCG & PAPP-A :Blood test between

9+0 and 13+6 weeks (ideal between 10-11 weeks)

*Nuchal Translucency measurement: Ultrasound performed

between 11+1 and 13+6 weeks (CRL 45 - 84mm)

*Nasal bone measurement

*Maternal age (& maternal weight)

Combined First Trimester Screening

• High risk cut off: 1 in 300 (T21), 1 In 175 (T18), 1 in 100 (T13)

• 93% detection of Down syndrome (2.9% FPR)*

• Low PAPP-A comment now included on reports:

“For a low PAPP-A result of less than 0.45 MoM, a referral should be made to an O&G specialist by 20 weeks gestation for assessment regarding the need for closer maternal and fetal surveillance”

• Results available 2-3 working days after scan received by VCGS

• Out-of-pocket for the blood test is approximately $70.00

*Based on 2013 data

Prenatal screening pathway-options

NIPT following an increased risk on cFTS

NIPT plus 12 week

ultrasound

NIPT plus cFTS simultaneously

NIPT only

‘First tier’ test‘First tier’ test ‘Second tier’ test‘Second tier’ test

From 10 weeks gestation onwardsFrom 10 weeks gestation onwards From 12 weeks gestationFrom 12 weeks gestation

~75% referrals~75% referrals ~25% referrals~25% referrals

‘First tier’ test‘First tier’ test

Prenatal screening pathway-options

NIPT following an increased risk on cFTS

NIPT plus 12 week

ultrasound (recommended)

NIPT plus cFTS simultaneously

(most comprehensive)

NIPT only (not

recommended)

‘Second tier’ test‘Second tier’ test

Pros: • Cheaper Cons: • No 12wk NT

ultrasound • No MSS

biochemistry

Pros: • 12 wk NT

ultrasound • Slightly cheaper Cons: • No MSS

biochemistry

Pros: • 12 wk NT

ultrasound • MSS biochemistry • Back-up if NIPT

fails Cons: • Two risks • Slightly more

expensive (~$70 for MSS)

Pros: • Have CFTS results

to base decision-making on.

Cons: • Timing

Consider: • High risk due to NT

> 3.5mm ?

What makes percept different?

Because percept is local

reporting time 3-5 business

days from receipt

Test performance

characteristics are equal to

all market providers

VCGS does not simply

“pipeline” report

All failed tests and high risk

results are fully interpreted

All patients having percept

have access to pre-test

counselling.

All high risk results are

discussed with the referring

doctor. Post test genetic

counselling is offered to all

patients

VCGS is a comprehensive

genetics service and can

perform all follow up testing

and counselling – continuity

of care.

VCGS screening resources

• VCGS website: www.vcgs.org.au

o All VCGS information brochures available on our website

o Maternal Serum Screening patient information brochures are available in

some other languages

o Genetic counselling available by phone or face-to-face at any point in

process of screening

• Genetic Support Network of Victoria

o www.gsnv.org.au

o For more information contact: (03 8341 6201)