First Trimester Down Syndrome Screening

Posted On: May 4, 2023 By CIW

What is Down syndrome?

Down syndrome, also known as trisomy 21, occurs when there is an extra chromosome 21 present in the cells of the fetus. This affects how your child develops and functions throughout life. About 1 in every 700 babies is diagnosed with Down syndrome: a rate of less than one percent. The likelihood of carrying a pregnancy with Down Syndrome increases with increasing maternal age: In a thousand pregnancies, at age 20 there would be one with Down Syndrome, at age 30 two, at age 35 three to four, and at age 40 ten.

Down syndrome can cause an array of medical problems such as heart defects, vision and hearing problems, blood disorders, digestive issues, musculoskeletal problems, obstructive sleep apnea, and hormonal problems. It is also common for babies with the syndrome to have developmental and intellectual disabilities, as well as mental health and emotional concerns. Each baby will have unique effects when it comes to Down syndrome, but it is possible for them to live healthy and happy lives with the proper interventions.

Invasive Screening for Down Syndrome:

The only ‘definitive’ tests for identifying or excluding a fetus with Down Syndrome are CVS (chorionic villus sampling) at 12 weeks or amniocentesis at 16 weeks. Both are associated with pregnancy loss rates of 3-4 in a thousand procedures but provide much additional genetic information regarding the health of the baby.

Non-Invasive Screening for Down Syndrome:

After 10 weeks of gestation, genetic matter (“cell-free DNA”) from the pregnancy can cross the placenta and enter maternal circulation. This can be sampled and used to raise or lower suspicion for chromosomal abnormalities, as well as identify the gender. Since it is only a maternal blood test, there is no association with pregnancy loss.

At 12 weeks of gestation, ultrasound can be used to identify the “nuchal translucency” (fluid area behind the baby’s neck) thickness, which normally is quite thin (a couple of millimeters, or the thickness of a dime). At the nuchal translucency sonogram, the presence or absence of the fetal nasal bone is also assessed; absent nasal bone may be correlated with an increased risk for chromosomal abnormalities.

Looked at together, reassuring 10-week bloods and 12-week nuchal translucency sonogram can dramatically either enhance or reduce suspicion for chromosome abnormalities.

Schedule an Appointment

Down syndrome can be difficult to navigate, but our award-winning team of Maternal Fetal Medicine specialists and OB/GYNS can help. To meet with our team and learn more, we invite you to contact our New York City office by calling or filling out our online form.

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

Comments are closed.