Every couple who conceives want the very best for their babies. If you have spoken to an older generation of parents, they might have shared with you their past experience with amniocentesis — an invasive procedure that involves introducing a needle into the pregnancy sac to obtain amniotic fluid. This fluid is then tested to ensure that the pregnancy is not affected by Down Syndrome. A practice that was offered in the past for older pregnant mothers because they were at higher risk for Down Syndrome babies, amniocentesis can unfortunately result in miscarriages in 1 in 100-200 women.
While Down Syndrome babies are born more frequently to older mothers, younger women may still be affected. Medical advances have seen the introduction of screening tests for not only Down Syndrome, but also other severe conditions (called fetal aneuploidies) that might affect the baby’s development including Trisomy 13 and Trisomy 18. Screening tests cannot tell directly if a baby is affected or not. Instead, screening tests allow the couple to estimate the risk of the baby being affected. If the estimated risk is high, further tests such as amniocentesis may be required to confirm the diagnosis. Couples who obtain a low risk result may be reassured that the pregnancy is likely to be unaffected, and chose not to pursue further investigations.
The modern practice for screening for Down Syndrome and other fetal aneuploidies has evolved rapidly over the past two decades. A blood test and an ultrasound scan to examine the baby during the 11th to 14th week of pregnancy (called combined testing, first trimester screening or OSCAR test amongst other names) is a well-established and recognised strategy to help identify pregnant mothers at risk. Apart from screening for Down Syndrome, the ultrasound scan can be used to accurately estimate the due date of the pregnancy and also allows for screening for other fetal malformations.
Non-invasive prenatal testing (NIPT) is a relatively recent development in Down syndrome and fetal aneuploidy screening. A blood sample is taken from the pregnant mummy which is then analysed for the small fragments of the baby’s DNA that circulates in the mother’s blood. The proponents of NIPT argue that NIPT can be more accurate in estimating the risk of Down Syndrome in the unborn baby. At the same time, NIPT is less likely to return an inaccurate result (called a false positive). The accuracy of NIPT varies depending on the disorder that is being tested.
To understand more about Down Syndrome and fetal aneuploidy screening including the use of NIPT, speak with your doctor who will discuss what might be suitable for you.