PRENATAL DIAGNOSIS · Prenatal diagnosis includes all aspects of embryonic and fetal diagnosis ......

PRENATAL

DIAGNOSIS Marzena Wiśniewska M.D.,Ph.D.

Chair and Depart. of Medical Genetics

Prenatal diagnosis

includes all aspects of embryonic and fetal

diagnosis

is indicated in about 8% of all pregnancies

At least 93% of prenatal tests provide

reassurance for the couple concerned, and

selective termination of pregnancy is

indicated in less than 7%

Prenatal diagnosis

It is important to outline to the couple the

limitations of the appropriate test or tests

and to remind them that no single test or

even combination can exclude all

abnormalities !

Identification of at risk

pregnancies

Factors identifiable prior to a pregnancy:

elevated maternal age

parental consanguinity

ethnic origin

maternal illness or medication

positive family history

population carrier screening

Identification of at risk

pregnancies

Factors identifiable during pregnancy:

abnormal ultrasound appearance

alphafetoprotein screening

other biochemical screening tests

polyhydramnios, oligohydramnios

maternal exposure to teratogens

Termination of pregnancy after prenatal

diagnosis

(22 genetic centers, Canada)

22222 women had indications for prenatal diagnosis

17599 women decided to have invasive prenatal diagnosis (79%).

Chromosome aberrations were found in 399 fetuses (2.2%)

184 women decided to have termination of pregnancy (1% from 17599)

Techniques for prenatal diagnosis

Non-invasive

Invasive

Non-invasive techniques

Ultrasound (USS).

Maternal serum screening

Fetal cells in the maternal circulation

(NIPT)

Magnetic resonance imaging (MRI) of the

fetus

Invasive techniques

Amniocentesis

Chorionic villus sampling and placental

biopsy

Cordocentesis

Fetoscopy

ULTRASOUND SCANNING (USS)

ULTRASOUND

First used as a method of prenatal diagnosis

in 1972 for anencephaly

Quality depends on experience of the doctor

and quality of the ultrasonograph

It can detect many major structural

anomalies , but not all, e.g. cleft palate

USS - application

Screening procedure (done in every

pregnant women) in 11, 20, 30 weeks

gestation

Detailed ultrasound is used when there are

risks for specific anomalies

USS 11-13 weeks gestation

Dating of pregnancy

Determining fetal viability

Detection of number of fetuses

Early diagnosis of major anomalies

Nuchal scanning (nuchal translucency, NT)

Nuchal translucency 11-13+6

weeks gestation

Subcutaneous accumulation of fluid at the back of the fetal neck is visualized by USS as increased nuchal translucency (NT) thickness (Nicolaides, 2004).

The NT thickness grows together with time of pregnancy and crown-rump length

After 14 week it is much more difficult to measure nuchal translucency

NT in 11-13+6 weeks gestation 95%

transabdominal

probe

5% transvaginal

probe

Crown – rump length 45-84 mm

NT - interpretation

NT thickness is associated with chromosomal abnormalities, wide range of cardiac defects and genetic syndromes

Nuchal scanning can identify more than 75% fetuses with Down syndrome (false positive results are 5%).

During the second trimester NT is usually absorbed, but in some cases it changes into nuchal edema lub cystic hygroma.

Kariotype of

fetus

No of cases NT>95 centile

normal 95 476 4 209 (4,4%)

Trisomy 21 326 234 (71,2%)

Trisomy 18 119 89 (74,8%)

Trisomy 13 46 33 (71,7%)

Turner s. 54 47 (87%)

Triploidy 32 19 (59,4%)

Others 64 41 (64,1%)

Total 96 127 4 767 (5%)

Other causes of increased nuchal translucency

thickness...

Single gene disorders (~100 syndromes)

Fetal cardiac insufficiency associated with heart defect and/or defect of big vessels

Venostasis of head and neck of the fetus due to compression

Abnormal or delayed development of lymphatic system

Abnormal lymphatic drainage in neuromuscular diseases of the fetus

Fetus anaemia or hypoproteinemia

Infections of the fetus causing anaemia or circular insufficiency

Changes of intercellular substance

Ultrasound markers typical for

trisomy 21

USS markers LR for isolated markers

Shortening of humerus 4,1

Shortening of femur 1,6

Hydronephrosis 1,0

Hyperechogenic place in

heart

1,1

Hyperechogenic intestine 3,0

Big defects 5,2

Nasal bone

Another good ultrasound marker of Down

syndrome is agenesis or hypoplasia of nasal

bone of the fetus – NB

NB (+), agenesis is described as NB(-).

67 % fetus with trisomy 21

55 % fetus with trisomy 18

34 % fetus with trisomy 13

11 % fetus with monosomy X

Congenital defects are markers

of chromosome abnormalities

The more defects are detected of the fetus

the higher risk of having chromosome

aberrations is observed

2 congenital defects – risk approx 10%, 3

defects – 30%, 4 defects – 50%, 5-7 defects

– 60-70%, 8 or more – approx 90%.

Congenital heart defects

Intestinal obstruction

X-ray with contrast

done after birth

Duodenal atresia

frequency 1/5000

40% in chromosome

abnormalities (trisomy 21)

Omphalocoele

frequency 1/3000

60% in chromosome

aberrations

Polycystis kidneys

Autopsy view

USS – new methods

Three- dimensional USS (3D).

Doppler assessment of flow and

echocardiography used in diagnosis of the

fetal heart

USS – 3D technique

Simian crease

4D - USS

Maternal serum screening

Involves the use of the unique fetal markers,

proteins made by the fetus during pregnancy

Alpha-fetoprotein (AFP)

Human chorionic gonadotrophin (beta-hCG)

Unconjugated estriol (uE3)

Inhibin A

PAPP-A (pregnancy-associated plasma protein

A)

First trimester screening

beta- hCG

PAPP-A

Pregnancy with trisomy 21 in 12 week:

beta-hCG

PAPP-A

False positive 5%

False negative 40%

Chromosome

Aberration

beta-hCG

PAPP-A

Trisomy 13

Trisomy 18

Aberration of sex

chromosome

Normal

First trimester screening + NT

measure For trisomy 21 – detection 86.3%, false

positive 5%

For all chromosome aberration detection

90%, false negative 6%

Computer complex analysis of the data +

factors such as smoking, age of the mother,

age of the pregnancy, maternal diabetes is

done

If the risk is > 1:300 the invasive methods

are indicated

Second trimester screening

beta-hCG + AFP + u(E3) – triple test

Rate of detection 50-75% pregnancy with

trisomy 21, false positive 5%

Combination of NT improves rate of

detection 85-90%, false positive 5%

Nowadays done quite rare

Fetal abnormalities with

elevated AFP

Open neural tube defects!

Eventration

Lethal skin disorders

Epidermolysis bullosa simplex

Aplasia cutis congenita

AFP AFP

Fetal cells in maternal circulation

1:1000 or 1: 10000 nucleated cells originate

from the fetus

(trophoblast cells, nucleated erythrocytes,

granulocytes).

Non-Invasive Prenatal Test

(NIPT)

DNA płodu

DNA matki

Cell-free fetal DNA

5-15 % pozakomórkowego DNA w układzie krążenia matki stanowi DNA płodu (cff DNA)

The aim of the test

Excluding the most common chromosomal

aberrations.

It is done with maternal blood containing

fetal DNA.

Detection over 99% aneuploidy of

chromosomes 21, 13, 18.

MRI of the fetus

Done in the 1st and in the 2nd trimester

Complementary invastigation to USS

Application: neural tube defects, cancer of the fetus, diaphragmatic hernia, intestinal obstruction

Often necessary before intrauterine fetus therapy

Invasive technique

Chromosome abnormalities

rutine cytogenetic

FISH, MLPA, aCGH

Single gene disorder

molecular diagnosis

AMNIOCENTESIS

Amniocentesis-indications

1. Increased risk of birth of a child with chromosome aberration:

Advanced maternal age (over 35 years old)

Previous child with chromosomal abnormality

Parental chromosomal abnormality (balanced translocations, inversions)

Fetal abnormality suggesting the presence of chromosomal abberation

Low maternal serum alpha-fetoprotein (MSAFP)

Psychologic reasons

2. Increased risk of birth of a child with anencephaly or spina bifida

Standard amniocentesis

15-18 weeks gestation

Risk of complications 1%

Timescale for results: 9 days - 3 weeks

Early amniocentesis is possible to be done

in 10 -14th week of pregnancy, but the risk

of complications is 2%

Chorion villus sampling (CVS)

11-13 weeks gestation

Risk of complications: 1-2%

Timescale for results: 7 days

Procedure of choice of DNA analysis

There is the possibility of causal association

between early CVS and transverse limb deficiency

Transverse limb deficiency due to CVS < 11 week

1/200, >11 week 1/5000 CVS done

Chorion villus sampling

Indications for CVS

The same as for amniocentesis, except increased

risk of birth of a child with neural tube defects

Is a procedure of choice for DNA analysis as

DNA can be extracted directly from trophoblast

sample (fragile X syndrome, DMD, Huntington

chorea, spinal muscular atrophy).

Cordocentesis (PUBS – percutaneous

umbilical blood sampling)

from 18 week of gestation to near term

risk of complications 2%

Cordocentesis - indications

USS detection of fetal abnormalities, suggesting the possibility of chromosomal aberration in the fetus (after the 18th week of pregnancy)

Prenatal diagnostics of blood diseases (haemophilia, beta - thalassemia).

Results’ verification in suspection of chromosomal mosaicism in the fetus on the ground of amniocentesis

Late application to prenatal diagnosis

Complications

Vaginal spotting/bleeding (1-4%) especially after transcervical approaches (TC)

Amniotic fluid leak causing oligohydramnios

TC procedures – intrauterine infection (<0.1%)

Increased risk for respiratory problems after amniocentesis eg.transient tachypnoe of the newborn

The procedure-associated pregnancy loss rate is estimated at 1.5-2%

Fetoscopy

Thank you for your attention