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Non-Invasive Prenatal Testing

non-invasive prenatal testing making an

informed decision

this video produced by KK Women's and

Children's Hospital and genetic Support

Foundation provides information about

non-invasive prenatal testing ni PT

what is non-invasive prenatal testing

non-invasive prenatal testing or ni PT

is an optional blood test that can be

performed beginning at around ten weeks

of pregnancy and can screen for certain

genetic conditions

how does ni PT work our blood contains

fragments of our DNA known as cell free

DNA when a woman is pregnant her blood

will also contain DNA fragments from the

placenta which has a genetic makeup that

is usually identical to that of the

developing baby by analyzing this DNA in

mom's blood it can be determined if

there is an increased or decreased

chance for certain genetic conditions

what conditions does ni PT screen for

though this testing began as a screening

for Down syndrome over time the list of

conditions being screened has grown

today in addition to Down syndrome ni PT

also screens for trisomy 18 and trisomy

13 and in some cases other conditions as

well the effects of the screened

conditions vary tremendously from very

mild to severe these conditions usually

do not run in families and with every

pregnancy there is some chance of one of

these conditions the chance that a

pregnancy is affected with a condition

depends on a number of factors including

the mother's age women of any age can

have a baby with one of these conditions

what can ni PT tell me about my

pregnancy

ni PT is a screening test that can

determine if the chance of certain

genetic conditions in a pregnancy is

higher or lower

since ni PT is a screening test and not

a diagnostic test it cannot give you yes

or no answers if results indicate a high

or increased chance then a diagnostic

tests such as amniocentesis can then be

performed if the patient desires to

determine whether the baby really has

the condition or not amniocentesis

however has a 0.3 percent chance of

miscarriage which is why not all women

who are found to be high-risk choose to

pursue it if the ni PT results indicate

a low or decreased chance the likelihood

the baby has the condition is lower but

not zero keep in mind that false

positives and false negatives do occur

with ni PT the chance of a false

positive or a false negative result

depends on the condition tested for how

does ni PT compared to the first

trimester screening FTS test ni PT and

FTS are both screening tests for Down

syndrome these two tests however have

different strengths and limitations

FTS involves analyzing moms blood for

protein markers as well as an ultrasound

in the first trimester this ultrasound

involves measuring a pocket of fluid at

the back of the baby's neck this

measurement is known as the nuchal

translucency NT

just like ni PT FTS provides information

regarding the chance of Down syndrome

trisomy 18 and trisomy 13 in addition to

these conditions the ultrasound

measurements taken during FTS can also

provide information that may suggest the

possibility of other genetic conditions

as well as provide an early screen for

some birth defects including heart

defects and neural tube defects

although the FTS may provide information

for a greater number of conditions ni

EPT is a more accurate screening test

for Down syndrome please remember that

the DNA analyzed in ni PT is placental

in origin

so discrepancies between the baby's DNA

and that of the placenta can occur

there is no prenatal genetic screen that

tests for everything even when the

results of ni PT or FTS indicate a low

likelihood there is still some chance of

a genetic condition or birth defect

if you decide to undergo prenatal

genetic testing your healthcare provider

can help you decide which prenatal

testing would be best for your specific

situation some factors that may help

answer this question are how far along

you are in your pregnancy your age at

the time of delivery your past medical

and family history some women would

prefer definitive answers and since ni

PT and FTS cannot provide that they may

choose to go straight to a more

definitive test such as amniocentesis

on the other hand some women may feel

comfortable with their chances of a

genetic condition or are confident that

even if the baby did have a genetic

condition it wouldn't alter their

pregnancy plans or they may prefer not

to face the decision of whether or not

to have an amniocentesis

if the FTS or ni PT comes back

indicating an increased chance for a

genetic condition especially since

amniocentesis has an associated risk of

miscarriage in these cases some women

may decide not to undergo any prenatal

screening so how do you decide about

prenatal testing the decision to undergo

any prenatal genetic tests is personal

and should reflect your values

personality beliefs and needs this

decision should be made in consultation

with a health care professional there

are many prenatal tests available and

your health care professional will be

able to determine based on a number of

factors which test is appropriate to

offer you your decision may be very

different than the path your friend or

neighbor might take and that's okay in

most cases prenatal genetic testing is a

choice and the best way to make a

decision that is right for you is to be

informed

you