Cystic fibrosis (CF) is an inherited condition affecting breathing and digestion and affects approximately 1 in 2500 babies. One in 25 Caucasians are carriers of CF. CF causes thick mucus which traps bacteria, resulting in recurrent infections that damage the lungs. Thick mucus in the gut also makes digestion of food difficult. Infants and children with CF require daily chest physiotherapy to clear mucus from their lungs, frequent courses of antibiotics, and the need to take medicine to aid digestion. Until recently many children with CF died in early childhood but now many live to be 30, 40 or more. There is no cure for cystic fibrosis but better treatments are under research and development. The gene that causes CF is called CFTR.

The test from VCGS will detect about 90% of people who are carriers of cystic fibrosis. If the tests show that you have one copy of a CFTR gene change (mutation) for cystic fibrosis, then you are a carrier of this condition – but a couple is only at risk of having a child with CF if both parents are carriers of the condition. Carriers do not show any symptoms of CF but if you are a carrier of this condition your partner will be offered testing to clarify the risks for your future children.

Fragile X syndrome (FRAX) is the most common cause of inherited intellectual disability affecting around 1 in 4000 babies. Approximately 1 in 150 people are carriers of FRAX. People with FRAX can have developmental delay, learning difficulties, anxiety, autism and epilepsy. The features of FRAX vary from mild to severe with males more likely to be severely affected than females. Some, but not all females can also be severely affected. There is no cure for FRAX although some educational, behavioural and medical interventions can improve outcomes. Some females who are carriers of FRAX may have early menopause.

Fragile X syndrome is caused by an increase in the length of a particular gene known as the FMR1 gene, located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. The Fragile X carrier test will tell whether you carry a change on your X chromosome, called a premutation. Women who carry a premutation may have a child with FRAX, but it is not certain. The VCGS test will detect about 97% of people who are carriers of FRAX. It is recommended that the female member of the couple is screened first with this combined test as FRAX testing is not necessary for the male partner. Female premutation carriers have a 1 in 2 chance of passing that X chromosome down, so if the female is a carrier, further investigation of the pregnancy is available to determine if the pregnancy will have Fragile X syndrome. Males can be FRAX carriers, but they cannot have a child with Fragile X syndrome. A male carrier’s daughters will all be FRAX carriers too, and they could be at risk of having children affected with FRAX in the future.

Spinal muscular atrophy (SMA) affects approximately 1 in 6000 babies. One in 40 individuals are carriers for SMA. There are two genes which cause SMA, called the SMN1 and SMN2 genes. SMA is a condition that effects nerves in the spinal cord and causes muscles to get weaker. There are four types of SMA. SMA Type I is the most severe. Babies with SMA Type I have weak muscles from birth and usually do not live past two years of age. SMA Types II and III progress more slowly than Type I. Most children with SMA Types II or III are unable to stand or walk without help. Children with Types II and III SMA can live into early adulthood, depending on the severity of the condition. People with SMA Type IV do not develop symptoms until adulthood.  There is no cure for SMA, however there are treatments and interventions available aimed at managing symptoms and improving quality of life.

The VCGS test will detect about 97% of people who are carriers of SMA. If the tests show that you have one copy of the gene change for spinal muscular atrophy, then you are a carrier of this condition – but a couple is only at risk of having a child with SMA if both parents are carriers of the condition. Carriers of SMA do not show any symptoms of the condition but if you are a carrier of this condition your partner will be offered testing to clarify the risks for your future children.

If you’d like to discuss these options further, I recommend you contact a genetic counsellor at Genetic Clinics Australia on 9528-1910 or www.geneticclinic.com.au. This is particularly important if you and your partner are related. If you have any Jewish ancestry, I recommend you contact Genetic Clinics Australia to find out which tests are most appropriate for you, such as Tay Sachs disease testing.

Down syndrome (trisomy 21) is a condition in which an extra chromosome 21 is carried in each of the cells of the body. Instead of the normal 46 chromosomes there are a total of 47 chromosomes. The extra chromosome 21 results in intellectual disability of varying degrees and may cause problems with the heart, kidneys, bowel, eyesight or hearing.

Although the chance of having a baby with Down syndrome increases with the mother’s age, babies with Down syndrome can also be born to younger mothers.

The following table indicates the risk of having a baby born with Down syndrome. The risk estimation is based on the age of the mother at the expected time of delivery.

Fragile X syndrome (FRAX) is the most common cause of inherited intellectual disability affecting around 1 in 4000 babies. Approximately 1 in 150 people are carriers of FRAX. People with FRAX can have developmental delay, learning difficulties, anxiety, autism and epilepsy. The features of FRAX vary from mild to severe with males more likely to be severely affected than females. Some, but not all females can also be severely affected. There is no cure for FRAX although some educational, behavioural and medical interventions can improve outcomes. Some females who are carriers of FRAX may have early menopause.

Fragile X syndrome is caused by an increase in the length of a particular gene known as the FMR1 gene, located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. The Fragile X carrier test will tell whether you carry a change on your X chromosome, called a premutation. Women who carry a premutation may have a child with FRAX, but it is not certain. The VCGS test will detect about 97% of people who are carriers of FRAX. It is recommended that the female member of the couple is screened first with this combined test as FRAX testing is not necessary for the male partner. Female premutation carriers have a 1 in 2 chance of passing that X chromosome down, so if the female is a carrier, further investigation of the pregnancy is available to determine if the pregnancy will have Fragile X syndrome. Males can be FRAX carriers, but they cannot have a child with Fragile X syndrome. A male carrier’s daughters will all be FRAX carriers too, and they could be at risk of having children affected with FRAX in the future.

Spinal muscular atrophy (SMA) affects approximately 1 in 6000 babies. One in 40 individuals are carriers for SMA. There are two genes which cause SMA, called the SMN1 and SMN2 genes. SMA is a condition that effects nerves in the spinal cord and causes muscles to get weaker. There are four types of SMA. SMA Type I is the most severe. Babies with SMA Type I have weak muscles from birth and usually do not live past two years of age. SMA Types II and III progress more slowly than Type I. Most children with SMA Types II or III are unable to stand or walk without help. Children with Types II and III SMA can live into early adulthood, depending on the severity of the condition. People with SMA Type IV do not develop symptoms until adulthood.  There is no cure for SMA, however there are treatments and interventions available aimed at managing symptoms and improving quality of life.

The VCGS test will detect about 97% of people who are carriers of SMA. If the tests show that you have one copy of the gene change for spinal muscular atrophy, then you are a carrier of this condition – but a couple is only at risk of having a child with SMA if both parents are carriers of the condition. Carriers of SMA do not show any symptoms of the condition but if you are a carrier of this condition your partner will be offered testing to clarify the risks for your future children.

If you’d like to discuss these options further, I recommend you contact a genetic counsellor at Genetic Clinics Australia on 9528-1910 or www.geneticclinic.com.au. This is particularly important if you and your partner are related. If you have any Jewish ancestry, I recommend you contact Genetic Clinics Australia to find out which tests are most appropriate for you, such as Tay Sachs disease testing.

Fragile X syndrome (FRAX) is the most common cause of inherited intellectual disability affecting around 1 in 4000 babies. Approximately 1 in 150 people are carriers of FRAX. People with FRAX can have developmental delay, learning difficulties, anxiety, autism and epilepsy. The features of FRAX vary from mild to severe with males more likely to be severely affected than females. Some, but not all females can also be severely affected. There is no cure for FRAX although some educational, behavioural and medical interventions can improve outcomes. Some females who are carriers of FRAX may have early menopause.

Fragile X syndrome is caused by an increase in the length of a particular gene known as the FMR1 gene, located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. The Fragile X carrier test will tell whether you carry a change on your X chromosome, called a premutation. Women who carry a premutation may have a child with FRAX, but it is not certain. The VCGS test will detect about 97% of people who are carriers of FRAX. It is recommended that the female member of the couple is screened first with this combined test as FRAX testing is not necessary for the male partner. Female premutation carriers have a 1 in 2 chance of passing that X chromosome down, so if the female is a carrier, further investigation of the pregnancy is available to determine if the pregnancy will have Fragile X syndrome. Males can be FRAX carriers, but they cannot have a child with Fragile X syndrome. A male carrier’s daughters will all be FRAX carriers too, and they could be at risk of having children affected with FRAX in the future.

Some people choose to do no additional prenatal testing at all. Perhaps the risk of these conditions are considered to be low, or because termination of pregnancy would not be considered under any circumstances. This is a completely appropriate decision that is entirely yours to make. I would still recommend routine pregnancy blood tests and a 20 week ultrasound, which we can discuss at your appointments.

Nuchal translucency (NT) scan (Between 11 and 14 weeks)

All babies have a small amount of fluid under the skin at the back of the neck. An excessive amount of fluid in this area is associated with a higher chance of having a baby with Down syndrome or other abnormalities such as heart or kidney problems. This amount of fluid can be measured by ultrasound and is called nuchal translucency, nuchal oedema or nuchal fold. If there is an excessive amount of fluid then further investigations will be recommended, usually in the form of invasive testing, such as a CVS. An ultrasound at this stage also has additional benefits including very accurate dating of the pregnancy, diagnosis of multiple pregnancy and the detection of many unrelated physical abnormalities. In most instances this ultrasound is done as an abdominal scan but if the area on the back of the neck cannot clearly be seen then a vaginal ultrasound will be recommended. Of course, you have the option to decline this type of examination if you prefer. In expert hands this technique has a sensitivity rate of 70% for detection of Down syndrome. The false positive rate is 5%. Most babies with an increased nuchal translucency are completely normal.

Non-invasive prenatal testing (NIPT):

Several non-invasive prenatal genetic tests are available, which all test a maternal blood sample from 10 weeks of pregnancy. These tests analyse fetal DNA found in the mother’s blood to detect Trisomy 21, Trisomy 18, Trisomy 13 and Turner syndrome and are alternatively referred to as cell free DNA tests. The test is >99% sensitive for the detection of these trisomies, and 92% sensitive for the detection of Turner syndrome. NIPT is known by several different names – the two most common are Harmony and Percept. I recommend all my patients consider NIPT as it is the best, non-invasive screening test for Down syndrome available.

Combined first trimester screening:

The combined first trimester test for Down syndrome involves combining the results of the nuchal translucency scan with the results of a blood test performed prior to the ultrasound. The combined first trimester test is specifically directed at detecting Down syndrome and Edward syndrome. Results of this testing are reported as low risk or increased risk. Increased risk results do not mean there is something wrong with the baby, just that additional testing can be performed to clarify the result. The sensitivity for detection of Down syndrome is over 90%. The false positive rate for this test is approximately 5%. Most babies with an increased risk on the combined first trimester test are completely normal.

Chorionic villus sampling (CVS)

Chorionic villus sampling or CVS involves passing a needle into the placenta between 10 and 13 weeks gestation. A small amount of placental tissue is taken and a chromosome analysis is then performed by the pathology laboratory. Results take approximately ten working days to become available. Some ultrasound centres will offer you the option of FISH testing. This is a very rapid test for Down syndrome with the result being available the following day at an additional cost. Further details of the actual procedure will be given to you if this is the option you choose. The sensitivity of CVS detection of Down syndrome is virtually 100%. The only exception would be a technical problem growing the placental cells in the laboratory. In these circumstances an amniocentesis may be required later in pregnancy but this is exceptionally unlikely. The risk of miscarriage from the procedure itself is 0.2%. You must remember that there is a risk of spontaneous miscarriage at this gestation of approximately 2%. The total risk is therefore 2.2% although only a small proportion of this risk of miscarriage is actually as a result of the CVS test. The false positive rate for detection of Down syndrome is 0%.

Amniocentesis:

Amniocentesis involves taking a small sample of amniotic fluid from around the developing baby at approximately 16 weeks gestation. Only a small amount of fluid is taken but this is enough for a full chromosome analysis to be performed. Results take approximately ten working days to become available. Some ultrasound centres will offer you the option of FISH testing. This is a very rapid test for Down syndrome with the result being available the following day at an additional cost. The risk of miscarriage from the procedure itself is approximately 0.1%. The risk of spontaneous miscarriage at this gestation is 0.5%. The total risk from the procedure and spontaneous miscarriage is 0.6%. The sensitivity of amniocentesis for detection of Down syndrome is virtually 100%. As with CVS, there may be a technical failure to grow the cells in the laboratory but this is extremely uncommon. The false positive rate for detection of Down syndrome is 0%.

This table summarises the sensitivity, false positive rates and risk of each test mentioned above.