CENTRE FORWOMEN’S ULTRASOUNDFirst Trimester Screening Options

CENTRE FOR WOMEN’S ULTRASOUND

cfwu.com.au

DR INDIKA ALAHAKOON

indika-alahakoon.com.au

Every pregnant mother wishes for a healthy baby. Using new technology, and the most recent research findings, we are happy to offer several screening and diagnostic tests to reassure parents regarding the risk of chromosomal and structural anomalies in their fetus.

What is Down Syndrome?

Also known as Trisomy 21, Down Syndrome is the most common chromosomal anomaly detected in the fetuses of live born children. It is the result of a change in the fetal chromosome number, which leads to an extra 21 chromosome in the fetal cells. This change in the chromosomes is associated with intellectual impairment, and in some cases, structural anomalies in the fetus.

While all women are at risk of a Trisomy 21 fetus, the risk does increase with the age of the mother. On average, one in 650 babies born in NSW will have Down Syndrome.

BELLA VISTA:

Norwest Private Hospital

Suite 108, 9 Norbrik Drive

Bella Vista NSW 2153

P: 02 9836 3558 F: 02 9836 3872

E: info@indika-alahakoon.com.au

WESTMEAD:

Suite 25, Level 1, 163-171 Hawkesbury Road

Westmead NSW 2145

P: 02 9687 5555 F: 02 9687 5722

E: info@cfwu.com.au

NUCHAL TRANSLUCENCY ULTRASOUND 11 – 14 WEEKS

What is a nuchal translucency scan?

The nuchal translucency scan is a non-invasive ultrasound which is performed to measure the amount of fluid present on your baby’s neck, and determine if there is any excess fluid. This assessment is important as helps in the diagnosis of potential fetal complications, including Down Syndrome. If our specialists detect any abnormalities, we will notify you of the risks, and discuss your options with you. Counselling and recommendations for non-invasive prenatal testing, or definitive tests such as amniocentesis or CVS (invasive confirmation of chromosomal complications) can be offered.

When is it recommended, and how is my risk

factor calculated?

The nuchal translucency scan is recommended between 11.5 and 14 weeks gestation, as this is the stage of the pregnancy when the thickness of the nuchal translucency fluid can be seen to be different from a chromosomally normally fetus.

When determining your risk of chromosomal complications, there are three main independent risk factors used. These include:

• The mother’s age

• The Nuchal translucency thickness in the fetus, and the presence of the nasal bone.

• The mother’s serum level of beta-hCG and PAPP-A

An assessment is also made of the fetal heart, including tricuspid regurgitance and blood flow in the fetal vessel ductus venous, as these are also used in decision-making.

NON-INVASIVE PRENATAL TESTING (NIPT)

A: MATERNAL BLOOD TEST COMBINED WITH A DATING SCAN AT 10 WEEKS, AND A FETAL EARLY MORPHOLOGY SCAN AT 12 WEEKS

OR

B: MATERNAL BLOOD TEST AND A FETAL EARLY MORPHOLOGY SCAN AT 12 WEEKS

What is NIPT?

NIPT is a genetic test for Trisomy 21 (Down Sydnrome), Trisomy 13 and Trisomy 18, as well as testing of the gender chromosomes. The main benefit of NIPT is that it has a 99.5% success rate in detecting Down Syndrome in the fetus.

It is important to note that approximately 25% of chromosome abnormalities in pregnancy, as well as major structural anomalies, are not detected by a NIPT test.

A 12-13 week first trimester fetal morphology scan is recommended as part of your first trimester screening with NIPT. This will give an opportunity for other chromosome or structural changes to be diagnosed.

As NIPT is a screening test, a non-conclusive result, or a positive result on NIPT should be followed up by chorionic villous sampling, or amniocentesis.

When you attend non-invasive prenatal testing (NIPT) at the Centre For Women’s Ultrasound, you will undergo a consultation to guide you toward the appropriate test, followed by a dating scan or the 12 week fetal anomaly scan. Maternal blood sampling for the NIPT test will be performed at the centre. You will be contacted directly to discuss the results. If further testing is required, we have the expertise to organise these tests for you.

AMNIOCENTESIS AND CHORIONIC VILLOUS SAMPLING (CVS)

What is Amniocentesis and Chorionic Villous Sampling?

Before either of these procedures are recommended, we may first recommend a nuchal translucency scan or NIPT.

Amniocentesis and chorionic villous sampling are the definitive diagnostic tests for pregnancies at a high risk for chromosome and other genetic abnormalities, such as Down Syndrome. These tests can confirm or exclude a chromosomal or genetic abnormality in a high risk fetus. We can perform amniocentesis and CVS, including early results, by using a technique called QF-PCR for chromosomes 13, 18, 21, X and Y within 24-48 hours.

The indications for testing include high risk results from the nuchal translucency scan, diagnosis of fetal abnormalities on the routine morphology scan, advanced maternal age, and a family history of inherited genetic conditions.

Amniocentesis involves collecting a sample of the amniotic fluid from the pregnancy sac. In order to collect this sample, a fine needle is used under ultrasound guidance of experience doctors. This test is generally performed between 15 and 19 weeks gestation, and does incur a slight risk of miscarriage.

CVS is performed earlier in the first trimester of pregnancy for chromosomal or genetic diagnosis. Under ultrasound guidance, a biopsy of the placenta is obtained through the abdominal wall. Occasionally transvaginal sampling has to be performed due to inaccessibility of the placenta from the abdomen. This procedure can be performed between 11 and 14 weeks gestation, and also carries a slight risk of miscarriage.

FOR FURTHER INFORMATION ON THESE SCANS AND MORE, PLEASE VISIT CFWU.COM.AU