Can Screening Detect all birth defects?

First trimester screening is not diagnostic, but it can be used to guide decision making. To determine whether the fetus has a chromosomal abnormality, amniocentesis or chorionic villus sampling (CVS) must be performed. These procedures carry a small risk of miscarriage and therefore have traditionally been recommended to women who are over 35 or who have a positive medical history.

How is Ultra-screen®/First Trimester Screening performed?

This screening requires a sonogram and maternal blood work performed between 11–14 weeks of pregnancy. The sonogram will confirm how far along your pregnancy is by measuring the fetal crown rump length (CRL). In addition, a measurement of the skin fold along the back of the baby's neck, called the nuchal translucency (NT), will be taken. A maternal blood sample is used to analyze two biochemical markers called free beta-human chorionic gonadotropin (hCG) and pregnancy associated plasma protein-A (PAPP-A), which are found in the blood of all pregnant women. In some pregnancies when the baby has Down syndrome, trisomy 18, or trisomy 13 there is extra fluid behind the baby's neck and the hCG and PAPP-A results are abnormal. Combining your age-related risk with the NT measurement and blood work provides a risk figure for Down syndrome and trisomy 18/13. The blood test and the NT measurement can detect approximately 91% of babies with Down Syndrome and 95% with Trisomy 18/13.

How accurate is Ultra-screen®/First Trimester Screening?

Because this is a screening test, a positive result (showing an increased risk) does not mean your baby has a problem. Further diagnostic tests are options for you to consider. Also, a negative or normal result (one that shows a decreased risk) does not mean the baby will not have Down syndrome or trisomy 18/13. The Ultra-screen®/first trimester screening detects about 91% of pregnancies in which the baby has Down syndrome and 95% with Trisomy 18/13. Finally, this screen is not designed to provide information about the possibility of other chromosomal conditions, nor about many other genetic syndromes, genetic disorders, birth defects, or causes of mental retardation.

Who should consider Screening?

The American College of Obstetricians and Gynecologists (ACOG) 2007 Position Paper acknowledges genetic screening as a viable option for all pregnant women as well as those 35 and over who choose not to have invasive testing. ACOG recommends that all pregnant women, regardless of their age, should have the option of diagnostic testing as well.

"This new recommendation says that the maternal age of 35 should no longer be used by itself as a cut-off to determine who is offered screening versus who is offered invasive diagnostic testing," noted Deborah Driscoll, MD, a lead author of the document and vice chair of ACOG’s Committee on Practice Bulletins-Obstetrics, which developed the Practice Bulletin with ACOG's Committee on Genetics and the Society for Maternal-Fetal Medicine.

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Risk Assessment Chart for Down Syndrome and Trisomy 18