PRENATAL DIAGNOSIS Prenatal diagnosis - PowerPoint Presentation

Slide1

PRENATAL DIAGNOSIS

Prenatal diagnosis

Many techniques are available to assess

the

growth and

developmental status

of the

fetus, including

Ultrasound

Maternal

serum

screening

Amniocentesis

Chorionic

villus

sampling

(CVS)

Ultrasonogrphy

Is a relatively noninvasive technique that uses high frequency sound waves reflected from tissues to create images. This approach may be

trans

abdominal

or

transvaginal

.

Transvaginal

ultrasound producing images with high resolution.

Important parameters

revealed by ultrasound include

Fetal age and growth

Presence or absence of congenital anomalies

Amount of amniotic fluid

Placental position and umbilical blood flow

Number of gestation

Fetal age and growth are assessed by

crown –rump length during the 5

th

to the 10

th

weeks of gestation .After that , a combination of measurements-including the

biparietal

diameter (BPD)

of the skull,

femur length

,

and

abdominal

circumference

are used.

Multiple

measurements of

these

parameters over time

improve the

ability to

determine

the extent of fetal growth

.

Congenital

malformations

that can be

determined

by

ultrasound are;

Neural

tube

defects,

anencephaly and

spina

bifida

A

bdominal

wall defects, such as omphalocele

Heart

and facial defects, including cleft lip and

palate.

Ultrasound can also be used to screen for

Down

syndrome

and

some

other

chromosome-related

abnormalities through a test called

nuchal translucency

.

This

test involves measurement of

the

translucent space at the

posterior

of the

baby’s

neck, where fluid

accumulates when Down

syndrome

and

some other abnormalities are present

.

The

test is performed at 11 to 14 weeks

of

pregnancy.

Information

from this test,

combined

with maternal

serum screening

test results and the mother’s

age.

Maternal Serum Screening

One

of the

first

of these tests assessed

serum

a

-fetoprotein

(

AFP

)

concentrations.

AFP

is

produced normally

by the fetal liver, peaks

at approximately 14

weeks, and “leaks” into the

maternal

circulation via the placenta.

Thus

, AFP

concentrations increase

in maternal serum during

the second

trimester and then begin a steady decline

after

30 weeks

of gestation.

In

cases of neural tube

defects,

omphalocele,

bladder

exstrophy

,

and other congenital malformations,

AFP levels increase in amniotic fluid and maternal serum.

In other instances, AFP

concentrations

decrease, as, for example

,

in Down syndrome

,

trisomy 18, sex chromosome abnormalities

,

and

triploidy

.

AFP

screening, combined with

testing

other second trimester markers

(

e.g.,

human

chorionic

gonadotropin

(HCG), unconjugated

estriol

,

and

inhibin

A

)

can increase the detection rate

for birth

defects using these serum screening studies.

Amniocentesis

During

amniocentesis, a needle is inserted

trans abdominally into

the amniotic cavity (

identified by ultrasound)

and approximately

20

to

30 mL

of

fluid

is withdrawn. Because of

the amount of fluid

required, the procedure is not

usually

performed

before 14 weeks’

gestation.

The fluid itself is analyzed for biochemical

factors , such as

AFP

and

acetylcholinesterase. In addition, fetal cells, sloughed into

the amniotic

fluid

,

can be recovered and used for metaphase

karyotyping and

other genetic

analyses.

Chorionic Villus

Sampling(CVS)

CVS

involves inserting a needle

transabdominally

or

transvaginally

into the placental

mass and aspirating approximately 5 to 30 mg of villus tissue.

Because

of

the large

number of cells obtained, only 2 to 3 days

in culture are necessary

to permit genetic analysis.

The risk of procedure-related pregnancy loss from CVS when performed by experienced

individuals appears to

approach that of amniocentesis.

Previously,

invasive procedures

,

such as

aminocentesis

and CVS

, were

offered

only to women at higher risk.

In recent years, risks associated with these procedures have decreased and, consequently, these procedures have been made more widely available.

Factors that place women at high

risk

include the following:

●

Advanced maternal age (35 years and older

);

●

Previous family history of

a genetic

problem

,

such as the parents

having

had a child

with Down

syndrome or a neural tube defect

;

●

The presence of maternal disease, such

as

diabetes;

●

An

abnormal ultrasound or serum screening test.

Fetal therapy

Modern

medicine has also made the fetus a patient who can receive

treatment, such as;

Fetal Transfusion

In cases of fetal anemia

, or

other causes produced by maternal

antibodies ,blood transfusions

for the fetus can be performed.

Fetal Medical Treatment

Fetal Surgery

Stem Cell Transplantation and

GeneTherapy

THANK YOU