Post by pinktorontogirl on Nov 29, 2006 15:39:31 GMT
to the thread to detail the different screening tests open to you, I hope that you will find this useful.
Screening tests are non-invasive tests that can be offered to all pregnant women. They are not diagnostic. Instead, they help to identify women where the chance of having a baby with Down's syndrome is greater than 1 in 250.
Nuchal Scan
Between 11 - 13 weeks of pregnancy the fluid at the back of the baby’s neck, the nuchal translucency, is measured. By combining the mother’s age with information from the scan an individual statistical chance of a chromosome abnormality can be given for that particular pregnancy. If the chance is more than 1 in 250 (although this does vary with different hospitals) a diagnostic test, such as CVS, will be offered.
Integrated Test
The integrated test is performed in two stages. In the first stage, at around 12 weeks of pregnancy, a blood sample is taken from the mother which measures the concentration of serum pregnancy associated plasma protein-A (PAPP-A) and a nuchal scan is also carried out. The second stage involves a second blood sample which is ideally taken at 15 or 16 weeks of pregnancy. Only after this second stage is a statistical result given. This blood sample measures four serum levels - alpha feto protein (AFP), unconjugated oestriol (uE3), free beta human chorionic gonadotrophin (freeß-hCG) and inhibin-A (inhibin). The measurement of the total six markers together with the mother's age are used to estimate her chances of having a pregnancy with Down's syndrome. Women with a chance greater than 1 in 100 are offered amniocentesis.
Triple Test
This test has many names - you may hear it called the Leed’s test, the Bart’s test, the double test or the blood test. A sample of blood is taken usually between 16-18 weeks of pregnancy. The stage of pregnancy is best estimated by an ultrasound dating scan. The number of substances measured will vary according to hospital policy but they will be a combination of alpha-fetoprotein (AFP), uncojugated oestriol (uE3) inhibin-A (inhibin) and free beta human chorionic gonadotrophin (free ß -hCG). The concentrations of these substances are used together with the mother’s age to estimate her chances of having a pregnancy with Down’s syndrome. The level of AFP is also used to determine if there is an increased chance of spina bifida or anencephaly. Women with a chance greater than 1 in 250 (although the figure does vary at different hospitals) are offered amniocentesis. One in every 20 women will be given a chance greater than 1 in 250.
Ultrasound
A detailed ultrasound. This is often performed in conjunction with the blood tests, and it checks the fetus for some of the physical traits associated with Down syndrome.
Ultrasound scanning is used routinely in all pregnancies to check the growth and development of the baby. It can also be used to identify certain characteristics or markers, which are often found in babies with Down’s Syndrome:
* Shorter arm and leg bones (femur & humerus)
* Sandal gap between the first (big toe) and second toes
* Heart defects
* Thickening or swelling at the back of the neck
Whilst the presence (or absence) of these markers cannot diagnose or rule out the possibility of the baby having Down’s Syndrome, if markers are seen they provide an indication and may be helpful in making decisions about further tests.
Screening tests are non-invasive tests that can be offered to all pregnant women. They are not diagnostic. Instead, they help to identify women where the chance of having a baby with Down's syndrome is greater than 1 in 250.
Nuchal Scan
Between 11 - 13 weeks of pregnancy the fluid at the back of the baby’s neck, the nuchal translucency, is measured. By combining the mother’s age with information from the scan an individual statistical chance of a chromosome abnormality can be given for that particular pregnancy. If the chance is more than 1 in 250 (although this does vary with different hospitals) a diagnostic test, such as CVS, will be offered.
Integrated Test
The integrated test is performed in two stages. In the first stage, at around 12 weeks of pregnancy, a blood sample is taken from the mother which measures the concentration of serum pregnancy associated plasma protein-A (PAPP-A) and a nuchal scan is also carried out. The second stage involves a second blood sample which is ideally taken at 15 or 16 weeks of pregnancy. Only after this second stage is a statistical result given. This blood sample measures four serum levels - alpha feto protein (AFP), unconjugated oestriol (uE3), free beta human chorionic gonadotrophin (freeß-hCG) and inhibin-A (inhibin). The measurement of the total six markers together with the mother's age are used to estimate her chances of having a pregnancy with Down's syndrome. Women with a chance greater than 1 in 100 are offered amniocentesis.
Triple Test
This test has many names - you may hear it called the Leed’s test, the Bart’s test, the double test or the blood test. A sample of blood is taken usually between 16-18 weeks of pregnancy. The stage of pregnancy is best estimated by an ultrasound dating scan. The number of substances measured will vary according to hospital policy but they will be a combination of alpha-fetoprotein (AFP), uncojugated oestriol (uE3) inhibin-A (inhibin) and free beta human chorionic gonadotrophin (free ß -hCG). The concentrations of these substances are used together with the mother’s age to estimate her chances of having a pregnancy with Down’s syndrome. The level of AFP is also used to determine if there is an increased chance of spina bifida or anencephaly. Women with a chance greater than 1 in 250 (although the figure does vary at different hospitals) are offered amniocentesis. One in every 20 women will be given a chance greater than 1 in 250.
Ultrasound
A detailed ultrasound. This is often performed in conjunction with the blood tests, and it checks the fetus for some of the physical traits associated with Down syndrome.
Ultrasound scanning is used routinely in all pregnancies to check the growth and development of the baby. It can also be used to identify certain characteristics or markers, which are often found in babies with Down’s Syndrome:
* Shorter arm and leg bones (femur & humerus)
* Sandal gap between the first (big toe) and second toes
* Heart defects
* Thickening or swelling at the back of the neck
Whilst the presence (or absence) of these markers cannot diagnose or rule out the possibility of the baby having Down’s Syndrome, if markers are seen they provide an indication and may be helpful in making decisions about further tests.