The OSCAR test is a standard first-trimester screening test for abnormalities or genetic diseases in the foetus. Most tests results are fine. But what if yours isn’t?
What was meant to be a routine prenatal screening test turned Marilyn’s (not her real name) world upside down. Then happily expecting her first child, she was offered the OSCAR (or One-stop Clinic for Assessment of Risk for Fetal Anomalies) test in her first trimester.
“My gynaecologist told me that it was a standard prenatal screening test for abnormalities or genetic diseases in the baby, with the most common being Down Syndrome (also known as Trisomy 21 or T21),” explains Marilyn. “As I faced a higher risk due to my age (35), I did the test as early as I could, at around week 11.”
The OSCAR combination test includes an ultrasound scan to assess the thickness of the skin in the neck of the foetus (known as Nuchal Translucency or NT) and a blood test. It is usually performed between the 11th and 14th weeks of the pregnancy. It has a 90 per cent accuracy rate.
Interpreting the OSCAR Test Results
When the results came back two days later, Marilyn was crushed. “The ultrasound showed that my baby did not seem to have a nasal bone and had a thickened NT (6.9mm compared to the normal thickness of less than 2.5mm). Together with my blood test results, I faced a very high risk of my baby having Down Syndrome.” Panic-stricken and in a state of shock, Marilyn was at a loss as to what to do next.
First, it is important to understand that the OSCAR test is not diagnostic. This means it cannot tell you if your baby has Down syndrome. The result, which comes in the form of a numerical risk value, only tells you if you belong in the low-risk (≥ 1:300) or high-risk (≤ 1:300) group.
If your result is 1 in 300, it means that one out of 300 women will have an affected baby – but it also means that the remaining 299 women with the same results will not have an affected baby. There are also incidences of false positives, where poor OSCAR results lead to births of normal babies with no fetal abnormalities at all. The false positive rate for Down syndrome is at 5 per cent.
“Like most women in their first pregnancies, I struggled just to understand the results,” shares Marilyn. “Fortunately, I had a good gynaecologist who explained the report thoroughly and put the risk in perspective.” If you’ve been handed bad news, don’t despair.
After OSCAR: Chart your Next Steps
Ask your gynaecologist to walk you through the report and explain your results in detail. You may then be recommended further prenatal screening, such as the NIPT (Non-Invasive Prenatal Testing).
This test, which is 99 per cent accurate, locates foetal DNA from a sample of the mother’s blood. This is then screened for genetic disorders like Down Syndrome, Edwards Syndrome (Trisomy 18 or T18) and Patau Syndrome (Trisomy 13 or T13). NIPT can also reveal the baby’s gender. In Singapore, there are two major companies offering the NIPT test – Harmony and Panorama.
Because the NIPT is newer and more accurate, it is often offered as an alternative to the standard OSCAR test. But cost is the main reason why some prefer the OSCAR to the NIPT. The former costs around $300 while the NIPT is around $1,000.
Women with poor OSCAR results may then be offered an opportunity to take the non-invasive NIPT before other more invasive diagnostic tests, such as Chorionic Villous Sampling (CVS) and amniocentensis, are recommended.
“My NIPT results came back with a very high risk of 1 in 9 for Down Syndrome, so my gynaecologist suggested following up with a diagnostic test so that we’d know for sure,” shares Marilyn. There were two options:
Marilyn said: “I was extremely distressed, and opted for the CVS as it could be done earlier. My husband and I also asked for a faster return of results — within two working days — as we could not bear the two-week wait.”
Unfortunately, the CVS also turned out be a stressful procedure for Marilyn. “During the ultrasound, it was discovered that my placenta was located at back of my uterus (posterior placenta). There was no way for the doctor to insert the needle so far back without hurting the foetus. It took three tries over two days just to retrieve the placenta sample.”
Moving On after Bad OSCAR Test Results
While the vast majority of babies do turn out normal, Marilyn’s baby was diagnosed with Down Syndrome. The couple then had to decide whether to keep the pregnancy.
“We made a carefully considered but heart-renching decision to terminate our much-wanted pregnancy at week 13,” shares Marilyn. “It was the toughest three weeks of our lives; we knew how easily we could be judged for it.”
Marilyn went through a medical termination, followed by a D&C (also known as a dilation and curettage) to remove the remains in the womb. “It was traumatic waking up in the maternity ward, surrounded by cheerful murals and newborn babies’ cries,” says Marilyn.
“What I felt afterwards was just emptiness. Now, almost a year on, grief still hits me in waves.”
Afterwards, Marilyn waited for the full results to see if this was a random occurrence or inherited (chromosomal translocation). She shares: “It was the former, so, it is unlikely that future pregnancies will be similarly affected.”
In her darkest days, Marilyn found non-judgmental advice and comfort from fellow mothers in online groups and overseas online forums. “There are not many of such stories being shared locally, unfortunately. I hope that mine will help expectant women who are going through similar situations.”