Download Maternal Screening

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)
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
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
Reporting and Interpretation of Results
• MoM (Multiples of Median) is a measure of how far an
individual test result deviates from the median
(medians are generated from the Indian subpopulation)
• 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),
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)
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
Reporting and Interpretation of Results
• 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
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