We, at Apollo Cradle & Children’s Hospital, know that the health of your unborn baby is your top priority. Therefore, we offer multiple screening tests including the Down Syndrome screening test. Not many know that Down syndrome can be easily detected while in the womb itself.
What Is Down Syndrome Screening?
Down syndrome is a genetic disorder that is caused when abnormal cell division results in extra genetic material from chromosome 21. Down syndrome causes a distinct facial appearance, intellectual disability, developmental delays and may be associated with thyroid or heart disease.
A test for Down Syndrome during pregnancy is offered to all women to assess the risk of the baby being born with this If your Down syndrome screening test shows a high risk, you will usually be offered a diagnostic test.
Combined First Trimester screening or NT scan:The vast majority of babies are normal. However, all women, whatever their age, have a small risk of delivering a baby with a physical or a mental abnormality such as Down syndrome. This condition is mainly looked for in the first-trimester screening.
Keep in mind that screening is not a diagnostic test; it is only a tool which indicates whether your baby has Down syndrome. The screening gives the probability of your baby having Down syndrome, trisomy 13, or trisomy 18.
The screening for Down syndrome involves an ultrasound assessment of the fetus for nuchal translucency (NT), which is a measurement of the fluid underneath the skin, alflow across the ductus venosus, the physiological valve regulating blood to the heart. It is advised to have the ultrasound at week 12 of pregnancy. However, the ultrasound can be performed at 11 weeks to 13 weeks and six days of pregnancy. It is a highly specialised ultrasound.
Blood Test – Although, the blood test can be performed up until 13 weeks and six days of pregnancy, it is recommended to have the blood test at week 10 of pregnancy. It analyses three chemicals found in the blood of all pregnant women – free beta-human chorionic placental growth factor (PLGF), gonadotropin (hCG), pregnancy-associated plasma protein-A (PAPP-A).
The NT measurement, nasal bone data and blood flow data are combined your age-related risk to arrive at one risk figure for Down syndrome and one risk figure for trisomy 13 or trisomy 18.
As this is only a screening test, a positive result (showing an increased risk) does not mean that your baby has an issue, only that further diagnostic tests are options for you to consider. Similarly, a negative or normal result (one that shows a decreased risk) does not mean that your baby will not have a chromosome abnormality. It is important to remember that most women will have normal babies, even if they are grouped as high risk.
If the screening test result positive, the following options are available:
- Diagnostic test by chorionic villus sampling (CVS) performed between 10-13 weeks,
- Diagnostic tests by amniocentesis are performed after 15 weeks
- Second-trimester maternal serum is drawn for screening after 15 weeks and a result combining first, and second-trimester is obtained
- Detailed anatomy ultrasound is performed at approximately 18-20 weeks.
Diagnostic tests such as CVS and amniocentesis can tell you whether or not a baby has a chromosome abnormality with more than 99% accuracy. While the final results of the chromosomal analysis may take 2-3 weeks, interim results may be available in a few days.
Couples or individuals may elect not to proceed with additional tests for various reasons. They may be comfortable with the results irrespective of the outcome or may choose to avoid any testing that poses a potential risk of harming the developing baby. It is important to discuss the risks and benefits of testing thoroughly with your doctor.