Integrated Test: One of the most important tools for prenatal care.

Why is age taken into account?

The chances of a woman having a baby with Down Syndrome increases with her age. For this reason, age is one of the important factors in calculating the risk of a Down Syndrome pregnancy. An older woman is more likely to screen as positive and be offered a diagnostic test. This is shown in the table below.

Maternal Age Group (years)	Probability of a screen-positive result	Proportion of Down Syndrome pregnancies detected (%)
15 - 34	1 in 130	81%
35 and over	1 in 25	92%
All	2 in 100	90%

What is the Integrated Test?

The Integrated Test is a blood screening for pregnant women. The test identifies women who are at high-risk for having a baby with Down Syndrome, open neural tube defects and other birth defects. The Integrated Test is performed in two stages:

The first stage is performed between the 8th and the 13th week of pregnancy and involves:

• An ultrasound scan examination to determine the gestational age of the pregnancy
• A blood sample to measure the concentration of a protein called pregnancy associated plasma protein-A (PAPP-A)
• An appointment for an ultrasound nuchal
  translucency measurement

The second stage is performed between the 15th and 22nd week of pregnancy. It involves another blood sample to measure the concentration of the following four substances:

• Alpha-fetoprotein (AFP)
• Unconjugated estriol (uE3)
• Human chorionic gonadotropin (ß-hCG)
• Inhibin-A (inhibin)

The measurements from the first and second stages are integrated into a single screening result. The nuchal translucency measurement and the levels of the five markers in your blood are used, together with your age, to estimate your risk of having a Down Syndrome pregnancy.

Why is there another test at the second stage?

By using information from both stages, the test is safer and more effective than results from the first stage alone. The Integrated Test results will distinguish between affected and unaffected pregnancies more effectively, thereby reducing the chance that a Down Syndrome pregnancy is missed. It also reduces the likelihood that you will need an invasive diagnostic test, such as amniocentesis.

What is Down Syndrome?

Down Syndrome is the most common cause of severe mental disability and is often associated with physical problems, such as heart defects or difficulty with sight and hearing. It involves a pattern of birth defects and mental retardation, occurring in about one in every 700 births. Down Syndrome is a disorder in which an extra chromosome number 21 is present in the cells of the developing fetus. It occurs unexpectedly and is usually not inherited. About nine of ten babies with Down Syndrome will survive their first year, and nearly half of these will reach age 60. It is not possible to assess the degree of handicap before the baby is born.

What are neural tube defects?

Neural tube defects are birth defects that affect the brain and the spine. One or two babies out of 1,000 are born with a neural tube defect. These defects involve failure of bony tissue to close properly. The two most common defects are spina bifida and anencephaly.

Spina bifida usually causes some degree of paralysis from the waist down and may interfere with bowel and bladder control. It often leads to a condition called hydrocephalus (water on the brain) and can sometimes cause mental retardation. Almost one-third of the babies born with open spina bifida will not survive past age five. Anencephaly is a very serious defect that occurs when a baby’s brain and skull fail to develop properly. Babies born with this condition do not survive more than a few days.

Can other abnormalities be identified?

Yes. The risk of other disorders can be identified. Trisomy 18 Syndrome, also known as Edwards’ Syndrome, is a rare and usually fatal disorder caused by the presence of an extra chromosome number 18 in the cells of the developing baby. The risk of Trisomy 18 Syndrome is reported only when the risk is high.

What does a negative screen result mean?

A negative screen result means that you are not at high risk of having a baby with Down Syndrome or a neural tube defect, but it does not rule out the possibility of a pregnancy with either of these abnormalities.

What does a positive screen result mean?

A positive screen result means that you are in a higher risk group for having a baby with Down Syndrome. The risk of Down Syndrome in your pregnancy is 1 in 270, and you will be offered a diagnostic amniocentesis. About two in every 100 women screened will be in this risk group. Most women who screen as positive, however, do not have a Down Syndrome pregnancy.

A positive screen result can also mean that you are at increased risk of having a baby with an open neural tube defect. If your result is in this group, you will be offered an ultrasound scan examination at the 18th to 20th week of pregnancy, and possibly, an amniocentesis.

What is an Amniocentesis?

Amniocentesis is a medical procedure in which a small amount of fluid is withdrawn from the sac surrounding the fetus in the uterus. This fluid sample is used to diagnose the existence of chromosomal disorders, such as Down Syndrome and Trisomy 18 Syndrome, as well as open neural tube defects, such as spina bifida. Amniocentesis is an invasive procedure, meaning that there is a small risk of miscarriage (less than 1 in 200) associated with it.

No test can guarantee that your baby will be free of all birth defects. If, however, the amniocentesis result is negative, it will almost certainly rule out the presence of Down Syndrome or other chromosomal abnormalities.