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Sequential Screen and Quad Screen

Background

The Sequential Screen and Quad Screen are two non-invasive tests offered to patients to screen for three different conditions: Down Syndrome (also known as Trisomy 21), Trisomy 18 and neural tube defects. Down Syndrome and Trisomy 18 are caused by an additional chromosome in your baby’s cells and lead to mental retardation. The risk for having a baby with Down Syndrome or Trisomy 18 increases with the mother’s age, and is not dependent on the age of the father.

Neural tube defect/Spina Bifida is a condition in which the spine does not close correctly and the baby is born with permanent nerve damage to the spinal cord, which can cause lifelong problems with walking, urinating and bowel movements. These tests are performed by drawing blood from the mother at specific intervals during the pregnancy.

Sequential Screen

The Sequential Screen is a two-part test.

The first part of the test is an ultrasound performed in the first trimester between 10 weeks and five days and 13 weeks and six days and must be scheduled in advance. During the ultrasound, the sonographer takes a special measurement, called the nuchal translucency (NT).

This ultrasound must be performed at the office of perinatologists (medical doctors who specialize in high-risk obstetrics), Maternal Fetal Medicine in the Levy Medical Plaza at 1245 Old York Road, Suite G18 (across from Abington Memorial Hospital.)  The Levy Medical Plaza is accessible from Abington Memorial Hospital via the Levy Link.

Following the ultrasound, blood work is drawn in the lab across the hall in Suite G13. The lab sends the sample and NT measurement to Genzyme Genetics for interpretation. The results of the first part will be sent to our office. If the first part of the test is abnormal, you will be notified and instructed to follow up with the perinatologists to review your options for further testing.

The second part of the test is a blood test, performed during the second trimester (between 15 and 20 weeks). The optimal time to have your blood drawn is between 16 and 18 weeks. The blood will be drawn at the same lab as during the first part of the test. You should pick up a lab slip at the Maternal Fetal Medicine office (Suite 119), prior to reporting to the lab.  No appointment is needed and you do not need a second ultrasound for this part of the test.

The results of the first and second parts of the Sequential Screen test are combined to provide you with your baby’s risk for Down Syndrome, Trisomy 18 or a neural tube defect.

By undergoing both parts of the Sequential Screen, approximately 92 to 95 percent of fetuses with Down Syndrome and 90 percent with Trisomy 18 can be detected. The neural tube defect detection rate is approximately 80 percent. When combined with the second semester ultrasound, the detection rate is over 95 percent.

Quad Screen

Sometimes the Sequential Screen cannot be performed if you are more than 13 weeks and six days pregnant. In this circumstance, you will be offered the Quad Screen, which is a blood test performed between 15 and 20 weeks. This test also calculates your baby’s risk for Down Syndrome, Trisomy 18 and neural tube defects. The detection rate is 80 percent for Down Syndrome, 80 percent for Trisomy 18 and 80 percent for Spina Bifida/neural tube defect.

If either the Sequential Screen or the Quad Screen indicates an increased risk for one of these disorders, you will be notified. This does not mean your baby has Down Syndrome, Trisomy 18 or a neural tube defect. It means that the test was abnormal and more specialized testing will be offered to you to determine if you baby has any of these conditions.

Remember, both the Sequential Screen and Quad Screen are noninvasive tests and will not place your baby at an increased risk for miscarriage. These tests are not required, but rather as an option for all pregnant patients.

If you are interested in the Sequential Screen, you must call 215-481-4944 as soon as possible to schedule the test. The test is performed only with perinatologists because only accredited ultrasonographers can perform the nuchal translucency measurement. The test must be performed between 10 weeks and five days and 13 weeks and six days. It may take two to three weeks to obtain an appointment for the test, so please call to schedule an appointment as soon as possible.

Call our office for results from the first part of the Sequential Screen if you have not been contacted within two weeks. The nurse will review your results and remind you when the second part of the test should be performed.

Both parts of the Sequential Screen are drawn in the lab located in the Levy Medical Plaza, Suite G13, across the street from Abington Memorial Hospital. The Quad Screen blood test may be performed at any lab.