Maternal Screening

Tests included in task force list:

1. First trimester screening by FMF

2. Quadruple marker

3. Trisomy confirmation

4. NIPD (Non-invasive Prenatal Diagnosis)

Targeted Specialties Gynecologists (Obstetricians) IVF specialists

Stages of Pregnancy • First Trimester – First 3 months (first 12 weeks of

pregnancy) • Second Trimester – Next 3 months (13 to 27 weeks) • Third Trimester – Final 3 months (28 weeks to 40 weeks) What is maternal screening? • Certain tests done in pregnant women to identify pregnancies

at higher-than-average risk of certain serious birth defects

• Also called prenatal screening • Clinical significance – Guides course of action for abnormal

pregnancies (including termination of pregnancy in some cases)

First Trimester

Screening

First Trimester Screening Test @ Metropolis Dual or Double Marker Test (with or without NT)– This includes

• Free β hCG (Free Beta Human Chorionic Gonadotropin) • PAPP - A (Pregnancy Associated Plasma Protein – A)

What is NT? • NT stands for Nuchal Translucency • It is a measurement of the fluid underneath the skin along

the back of the baby’s neck • It is measured by ultrasonography

Free β hCG (Free Beta Human Chorionic Gonadotropin) • Human Chorionic Gonadotropin (hCG) is a glycoprotein hormone normally produced

by placenta during pregnancy

• Very early in pregnancy, it is the substance used in pregnancy tests

• Consists of two subunits – alpha and beta chain subunits

• There is a significant increase in the level for free beta hCG subunit in Trisomy 21

cases; the levels are lower in Trisomy 18 cases

PAPP - A (Pregnancy Associated Plasma Protein – A) • As the name suggests, is an important pregnancy protein

• The main site of synthesis during pregnancy is placenta. The levels in pregnancy are

150 times higher than those in non-pregnant states

• Maternal serum levels of PAPP-A in the first trimester are significantly reduced when

a fetus affected by Trisomy 21 or Trisomy 18 is present

When is Dual marker done? • The first trimester test is generally done between 11 weeks

and 14 weeks of pregnancy

What does the test detect? • Dual or Double marker test in first trimester, identifies

pregnancies that have a high risk of babies having the following chromosomal abnormalities: • Trisomy 21 (Down’s syndrome) • Combined Trisomy 13 (Patau syndrome)/ Trisomy 18

(Edwards syndrome)

Remember,

This test is NOT a diagnostic test (it cannot tell whether the baby has any of

the above conditions); it only identifies the risk of the baby being affected. A

confirmatory test may be needed when the screening test is positive (high

risk)

This test is NOT a diagnostic test (it cannot tell whether the baby has any of

the above conditions); it only identifies the risk of the baby being affected. A

confirmatory test may be needed when the screening test is positive (high

risk)

Downs syndrome or Trisomy 21 • Babies with Down syndrome have an extra chromosome

number 21 (3 chromosome 21 instead of normal 2 chromosome 21)

• Causes mental retardation and other medical problems involving the heart, GI system and/or other organs

Trisomy 18/13 • More severe than Down syndrome • Cause profound mental retardation and severe birth

defects in many organ systems • Few babies with trisomies 13/18 can survive more than a

few months

Although anyone can have a baby with these chromosomal abnormalities, the chances increase with mother’s age

Although anyone can have a baby with these chromosomal abnormalities, the chances increase with mother’s age

Who should be screened?

• Ideally all pregnant women should be screened in first trimester for dual marker and if not done should have a quadruple marker screen

• However, if any of the following risk factors are present one should strongly consider having the test:

– age 35 or older pregnant females

– family history of birth defects

– previous child born with a birth defect

– History of insulin-dependent (type 1) diabetes prior to pregnancy

Reporting and Interpretation of Results

Report is generated by PRISCA. This is a software for risk calculation

• MoM (Multiples of Median) is a measure of how far an individual test result deviates from the median (medians are generated from the Indian sub- population) • 1/250 risk means 1 out of 250 women having similar results and history, one may have abnormality • Trisomy 21: screen positive (below 1/250) • Trisomy 18/13: for screen positive (below 1/100),

Reporting and Interpretation of Results

Detection Rate First trimester- NT measurement, PAPP-A. free beta HCG – 82 to 87%

First Trimester

Screening by FMF

(Fetal Medicine

Foundation)

• The FMF has set up a process for certification in the measurement of fetal

NT to ensure that those performing this ultrasound examination have been

adequately trained to do so and that high standards of performance are

maintained by continuous education and audit

• Once the FMF Certificate of competence in the measurement of NT has been

obtained, the doctor/sonographer will be entitled to receive free of charge

the FMF software for the calculation of risk of chromosomal abnormalities

by a combination of maternal age, fetal NT and first-trimester maternal

serum free β-hCG and PAPP-A

• The only condition for ongoing certification and use of the software is

provision of NT data and images by the sonographer for the purposes of

audit

• FMF has defined guidelines and protocols for NT measurement and this

protocol is widely respected globally

• Regular audits of NT images are mandatory

• Perkin Elmer is the market leader in India for screening by FMF

• It is said to have a detection rate of around 90% for Down syndrome at a

false positive rate of 5%

Second Trimester

Screening

Second Trimester Screening Tests @ Metropolis

Triple Marker Test (Also called triple screen) - This includes

• AFP (Alpha-fetoprotein) • uE3 (unconjugated Estriol) • hCG (Human Chorionic gonadotrophin)

Quadruple Marker Test (Also called Quad screen) - This includes

• AFP (Alpha-fetoprotein) • uE3 (unconjugated Estriol) • hCG (Human Chorionic gonadotrophin) • Inhibin A

AFP (Alpha-fetoprotein)

• AFP is a substance made in the liver of the fetus and some amount gets

into the mother’s blood

• Measuring levels in maternal serum help in screening for Downs syndrome

or Edward syndrome or neural tube defects

• Normally, low levels of AFP can be found in the blood of a pregnant woman.

No AFP (or only a very low level) is generally found in the blood of healthy

men or healthy, non pregnant women.

• In men, non pregnant women, and children, AFP in the blood can mean

certain types of cancer, especially cancer of the testicles,

ovaries, stomach, pancreas, or liver are present

• AFP levels are increased in Neural tube defects and decreased in Down

syndrome and Edward syndrome

uE3 (Unconjugated Estriol) • Estriol is a hormone produced by the placenta, using ingredients made by the fetal

liver and adrenal glands

• Estriol levels are reduced in pregnancies with Down syndrome or Edward syndrome

Inhibin - A • Is a protein secreted by the ovary, and is designed to inhibit the production of the

hormone FSH by the pituitary

• The level of inhibin A is increased in the blood of mothers of fetuses with Down

syndrome

• A practical advantage of the use of inhibin A as a screening marker is the very small

change in average levels of inhibin A with increasing lengths of gestation between 15

and 18 weeks in women with unaffected pregnancies. Inaccuracies in estimating the

length of gestation will therefore have a much smaller effect on the calculation of risk

estimates than would be the case with a marker such as unconjugated estriol

When is Triple/Quadruple marker done? • The first trimester test is generally done between 14 weeks

and 22 weeks of pregnancy (Ideal time 15-17 weeks)

What does the test detect? • Triple or Quadruple marker tests identify pregnancies that have a

high risk of babies having the following abnormalities: • Trisomy 21 (Down’s syndrome) • Trisomy 18 (Edward syndrome) • Neural tube defects

Remember,

These tests are NOT diagnostic tests (they cannot tell whether the baby has

any of the above conditions); it only identifies the risk of the baby being

affected. A confirmatory test may be needed when the screening test is

positive (high risk)

These tests are NOT diagnostic tests (they cannot tell whether the baby has

any of the above conditions); it only identifies the risk of the baby being

affected. A confirmatory test may be needed when the screening test is

positive (high risk)

Neural Tube Defect (NTD)

• A NTD is an opening in the spinal cord or brain that occurs very

early in human development

• An NTD develops when the neural tube does not close

completely

• Two types – Open and Closed

• Open- Brain and/or spinal cord are exposed through a defect in

the skull or vertebrae

• Closed – The spinal defect is covered by skin

• Treatment depends on severity of complication. No treatment is

available for defects such as anencephaly (absence of a major

portion of brain); others may require aggressive surgical

management

Who should be screened?

• Ideally all pregnant women should be screened in first trimester for dual marker and if not done should have a quadruple marker screen

• However, if any of the following risk factors are present one should strongly consider having the test:

– age 35 or older pregnant females

– family history of birth defects

– previous child born with a birth defect

– History of insulin-dependent (type 1) diabetes prior to pregnancy

Reporting and Interpretation of Results

Report is generated by PRISCA. This is a software for risk calculation

• 1/250 risk means 1 out of 250 women having similar results and history, one may have abnormality • Trisomy 21: screen positive (below 1/250) • Trisomy 18: for screen positive (below 1/100)

• Neural Tube defects – cut-off 2.5 MoM of AFP

Reporting and Interpretation of Results

Summary Quadruple test

(2nd trimester)

Triple test

(2nd trimester)

Dual marker test

(1st trimester)

Screens for Trisomy 21, Trisomy 18, NTD

Trisomy 21, Trisomy 18, NTD

Trisomy 21 and Trisomy 18/13

Test period 14 to 22 weeks of gestation

14 to 22 weeks of gestation

9 to 13.6 weeks of gestation

Ideal time for test 15-17 weeks of gestation

15-17 weeks of gestation

10-11 weeks of gestation

Effect of Trisomy 21 on biochemical markers

Inhibin A increases, Beta HCG increases, AFP decreases & UE3 normal/ decreases

Beta HCG increases, AFP decreases & UE3 normal/ decreases

Free Beta HCG increases, PAPPa reduces

Sensitivity (Detection rate)

81 % 69% 85% with Age, Free HCG, PAPPa & NT

Test Requirements • Peripheral blood

• USG report including weeks of gestation, CRL measurements, Nuchal translucency measurements, presence or absence of nasal bone, BPD (biparietal diameter). single/twin pregnancy

• Family history or previous history of down syndrome pregnancies.

• Weight

• LMP (last menstrual period)

• Race, Smoking status, Diabetes (type 1 or gestational) status

• If invitro fertilisation (IVF) procedure done then age of egg donor

What if screening is positive for one of the anomalies? • It does NOT mean that the baby necessarily has one of these

conditions

• Additional testing such as Chorionic Villus Sampling (CVS) and Amniocentesis may be required

• CVS and amniocentesis are diagnostic tests that have greater than 99% accuracy in diagnosing whether the baby has or not a chromosomal abnormality

Trisomy confirmation

Sample collection

• Amniotic fluid: AF should always be aspirated under

ultrasound guidance by an experienced and skilled practitioner

between 13-17 weeks of gestation. Collect 20-30 ml of AF

in sterile centrifuge tube (15 ml capacity, screw cap). Do not

add any additives. Call for tubes

Sample collection

• Usually done at 10-12 weeks of gestation

• It is the preferred technique before 15 weeks of gestation

• Although it is normally done for testing for Downs syndrome,

overall, CVS can detect more than 200 disorders

What is Karyotyping? • It is also called chromosomal analysis

• Chromosomes are examined microscopically to identify

diseases caused by change in number &/or structure of the chromosomes

Karyotype image of Trisomy 21