Maternal-Fetal Screening

Multiple Marker Screening for Down Syndrome, Trisomy 18 and Open Neural Tube Defects


What is First Trimester Risk Assessment?

This screening involves an ultrasound, performed between 11 weeks, 4 days and 13 weeks, 6 days of pregnancy, to measure the width of the fluid-filled space at the back of the fetal neck, called the nuchal translucency. In addition, blood is drawn, usually from your finger, between 9 weeks, 0 days and 13 weeks, 6 days, to determine the level of the fetal proteins HCG and PAPP-A. This evaluation may indicate if your pregnancy is at a higher chance for Down syndrome, trisomy 13, or trisomy 18 syndromes. Approximately 85% of pregnancies affected with Down syndrome will have an increased risk or “screen positive” result (>1:270) on first trimester screening.

What is Maternal serum alpha-feto protein (MSAFP4/Tetra/Quad)?

This test is routinely performed during the second trimester between 15 and 22 weeks gestation. This screening has been considered to be the standard of care for many years. Second trimester screening involves measuring four uniquely fetal proteins (AFP, HCG, Estriol and Inhibin) from your blood. This test screens for Down syndrome, trisomy 18 and open neural tube defects in the pregnancy. Approximately 81% of pregnancies affected with Down syndrome will have an increased risk or a “screen positive” result on a second trimester screening test.

What is Integrated Screening?

This involves the measurement of the nuchal translucency by ultrasound and a blood draw in the first trimester for PAPP-A. You will not receive your test results at this time. Subsequently, you will have your blood drawn in the second trimester for AFP, HCG, Estriol and Inhibin. You will then receive your results. These results will assess your risk for Down syndrome, trisomy 18 and open neural tube defects. Approximately 92-95% of pregnancies affected with Down syndrome will have an increased risk or a “screen positive” result on an Integrated Screening test.

What is Sequential Screening?

This is similar to Integrated Screening, but results are shared with the patient after the first and second steps of the screening process. Approximately 91% of pregnancies affected with Down syndrome will present with an increased risk or a “screen positive” result on a Sequential screening test.

What is a Neural Tube Defect?

Very early in the pregnancy, the fetus forms a structure called the neural tube. This structure develops into the brain and spinal cord. Occasionally, the development of the neural tube can be interrupted, leading to a “neural tube defect.” A neural tube defect can prevent the brain and/or spinal cord from developing fully. Spina bifida and anencephaly are conditions that result from neural tube defects. The handicaps due to these conditions range from moderate to severe.

What is Down Syndrome?

Down Syndrome is a chromosome abnormality. Chromosomes contain the inherited information that instructs our bodies how to grow and develop. The correct number of chromosomes in each cell needed for normal human development is 46. Individuals with Down syndrome inherit one too many chromosomes. The extra number 21 chromosome is why you will sometimes hear Down syndrome called “trisomy 21.”

What is Trisomy 18?

Trisomy 18 (Edward’s Syndrome) is a chromosomal disorder in which a baby or a fetus has an extra number 18 chromosome. A pregnancy affected with trisomy 18 or an individual affected with trisomy 18 will have 47 chromosomes instead of the normal 46. Trisomy 18 causes severe mental retardation and birth defects. The median survival of individuals with trisomy 18 is 14.5 days. Only 5-10% survive the first year.

What if I am over age 35?

The risk of Down syndrome and certain other chromosomal abnormalities (including the fetal trisomy 18 and 13) increases as a woman gets older. If you will be 35 or older when the baby is born, ask your doctor about tests that can ensure detection of chromosome abnormalities – amniocentesis, early amniocentesis or chorionic villus sampling (CVS). All of these tests are available through Eastern Virginia Medical School.

What if my Multiple Marker Screening is normal?

The vast majority of patients have a normal (negative) screening test. If your results fall in the normal range, your doctor will receive a written report in one week. For all of the screening options, a normal test result cannot guarantee a normal baby or pregnancy. However, a normal test result can reassure you. It means the chance of having a child with a neural tube defect, trisomy 18 or Down syndrome is not increased.

What if my Multiple Marker Screening is not normal?

A positive test does not necessarily mean that your baby will have a birth defect or other problem. It will prompt your doctor and others to look more closely at the pregnancy and refer you for genetic counseling to discuss further testing options.

What is the Ultrasound Risk Assessment for Down syndrome (URAD)?

Approximately 50% of Down syndrome fetuses will exhibit a fetal anomaly or a “marker” for Down syndrome. This evaluation is done between 18-22 weeks gestation. URAD may be able to improve the risk assessment determined from other screening tests.

What is genetic counseling?

Genetic counseling is an educational process that seeks to assist affected and/or at risk individuals to understand the nature of the genetic disorder, its transmission and the options open to them in management, testing and family planning.

Eastern Virginia Medical School

Eastern Virginia Medical School (EVMS) is the referral center in Hampton Roads for specialized services in obstetrics and gynecology, and clinical genetics.

EVMS’s laboratories provide the highest quality of patient care. These laboratories are fully licensed and are headed by board-certified physicians and scientists.

The Division of Maternal-Fetal Medicine at EVMS provides the region’s largest and most comprehensive physician group trained in the diagnosis and management of high- risk pregnancies. Patients referred to the Division of Maternal-Fetal Medicine receive complete genetic counseling and support from the program’s highly qualified genetic counselors and physicians.
 

This information is not intended to substitute or replace the professional medical advice you receive from your physician. The content provided on this page is for informational purposes only, and was not designed to diagnose or treat a health problem or disease. Please consult your physician with any questions or concerns you may have regarding a medical condition.