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Screening Tests

Sequential Integrated Screening

Sequential integrated screening is noninvasive testing offered by the state of California to all pregnant women. It is performed in multiple steps.

In the first step, which is performed between 10 and 14 weeks of pregnancy, a maternal blood sample is taken and an ultrasound scan is performed to measure the amount of fluid at the back of the baby's neck (nuchal translucency, or NT). If you complete the blood test before the scheduled ultrasound, you can receive an instant result at the conclusion of the ultrasound appointment.

The results of the blood test, the NT measurement and the mother's age are used to estimate the risk for Down syndrome and trisomy 18. The estimated detection rate for Down syndrome is 75 percent, and based on adjusted risk, a woman has the option of undergoing chorionic villus sampling (CVS) or amniocentesis for diagnosis.

The second step of sequential integrated screening is a maternal blood test between 15 to 20 weeks of pregnancy. When the results of this blood test are combined with the results from the first trimester blood test and NT ultrasound, the detection rate for Down syndrome increases to 90 percent. This test also provides a personal risk assessment for having a fetus with trisomy 18, Smith-Lemli-Opitz syndrome, an open neural tube defect or an abdominal wall defect. Based on the results, a woman has the option of undergoing amniocentesis.

Serum Integrated Screening

Serum integrated screening is a combination of the two maternal blood tests without nuchal translucency. The detection rate for Down syndrome is 85 percent. This test also estimates the probability of trisomy 18, Smith-Lemli-Opitz syndrome, and an open neural tube defect or abdominal wall defect.

Quad Screening or Second Trimester Screening

This is a maternal blood test done between 15 to 20 weeks of pregnancy. The test estimates the probability of Down syndrome, trisomy 18, Smith-Lemli-Opitz syndrome, and an open neural tube defect or abdominal wall defect. The detection rate for Down syndrome is 80 percent.

A positive result on a screening test indicates an increased risk for a genetic abnormality.

 

Reviewed by health care specialists at UCSF Medical Center.

This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.