Down Syndrome Screening Results: What Does 1:249 Mean?

Down syndrome screening

Doctor, I had my first trimester Down syndrome screening at 12 weeks and 2 days, and my risk value showed 1 in 249, while the background risk was 1 in 1028.
Is this normal?

Miss Wang, 20~29 year old female. Ask Date: 2024/01/07

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, the risk has increased.
It is recommended to consult your obstetrician to see if amniocentesis is necessary.
Wishing you good health.

Reply Date: 2024/01/07

More Info

When interpreting the results of Down syndrome screening, particularly the ratio of 1:249, it's essential to understand what this number signifies in the context of prenatal screening. The ratio indicates the likelihood of the fetus having Down syndrome based on the combination of maternal age, blood tests, and ultrasound findings. In your case, a result of 1:249 means that out of 249 pregnancies with similar characteristics, one is expected to have a fetus with Down syndrome.
To put this in perspective, the background risk of 1:1028 indicates that, in a general population of women with similar age and other factors, the likelihood of having a baby with Down syndrome is lower than your result. This means that your risk is higher than the average population risk, but it does not mean that your baby has Down syndrome. In fact, a 1:249 risk translates to approximately a 0.4% chance of having a baby with Down syndrome, which is still relatively low.

It's important to remember that screening tests are not diagnostic. They are designed to identify pregnancies that may be at higher risk, prompting further testing if necessary. If you have concerns about the results, you may want to discuss them with your healthcare provider. They might recommend additional diagnostic testing, such as chorionic villus sampling (CVS) or amniocentesis, which can provide more definitive information about the presence of Down syndrome or other chromosomal abnormalities.

In terms of what to do next, it’s advisable to have a thorough discussion with your obstetrician or a genetic counselor. They can help you understand the implications of your screening results, discuss your options, and provide support as you navigate this process. They can also explain the benefits and risks associated with further testing, helping you make an informed decision that aligns with your values and preferences.

In summary, while a 1:249 risk for Down syndrome is higher than the average background risk, it is still a relatively low probability. Engaging in open communication with your healthcare provider will be crucial in determining the best course of action for you and your baby.

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