A scan is done at the same time to guide the position of the needle. The type of sample collected depends on how many weeks pregnant you are see the diagrams below. Chorionic villus sampling — before 14 weeks, a sample of the developing placenta whenua is taken.
Amniocentesis — from 15 weeks, a sample of amniotic fluid the waters around the baby is taken. Diagnostic testing is your choice. For every women who have diagnostic tests, one or two will have a miscarriage. For this reason, some women choose not to have diagnostic testing. Your specialist will receive the test results in about two weeks. If your baby is found to have Down syndrome or another condition, your midwife, doctor or specialist will provide you with information and support.
You will be offered appointments with genetic services, a social worker or other services. You will be offered or given support to help you with any decisions that you may need to make. Diagnostic tests cannot tell you the range of abilities or challenges your baby may have.
If you would like more information, ask your midwife, doctor or specialist. For more information see www. The Health Information Privacy Code protects your personal details and gives you rights of access and correction.
As part of screening, information about you is collected and stored by the laboratories. This includes your name, address, ethnicity, weight and other information that helps to give accurate results. This information is held securely and confidentially. To maintain the quality of this screening, it is closely monitored.
The information may be used in published reports. These reports do not contain any information that identifies you in any way.
Skip to main content. Publication date:. National Screening Programmes. Pregnancy and newborn screening. Women's health. Screening programmes. View online Download PDF. Order free copies:. Information for pregnant women to help them make an informed decision about optional screening and testing for Down syndrome and other conditions.
Optional screening — your choice — your decision All pregnant women are advised of screening to assess the chance of their baby having Down syndrome or another condition. Antenatal screening for Down syndrome and other conditions During your pregnancy, you will be advised of screening for a number of conditions that may affect you or your baby. Screening and testing are your decisions Choosing whether to have this screening is an important decision.
Your midwife or doctor will discuss with you: the conditions that are screened for the differences between screening and diagnostic testing the risks and benefits of screening and testing what it may mean to have a child with one of the conditions being screened for where and when to get the blood test and scan, and any charges that may apply what the results may mean and the next steps.
You do not have to have screening and testing if you do not want to. What is Down syndrome also called trisomy 21? These problems may range from minor to severe and include: reduced muscle tone sight and hearing problems heart and bowel problems. What other conditions may be indicated by this screening?
Screening All pregnant women are advised about this screening. Image 1 - The blood test Image 2 - Having an ultrasound scan Image 3 - Nuchal translucency or NT scan showing the fluid-filled spaced at the back of the baby's neck. Structural abnormalities such as heart defects may be found when measuring NT.
These are caused by failures in the early development of the embryo. With NTDs the neural tube has failed to close fully, leaving a hole. If this results in absence of the brain it is anencephaly, if it leads to damage in the spinal chord it is spina bifida. Anencephaly is incompatible with life and only about half of those with spina bifida survive infancy. The extent of handicap due to spina bifida varies considerably but many have paralysis of the lower limbs and incontinence. Generally, there is no intellectual disability.
With AWDs it is the abdominal wall that has failed to close fully. As a result some of the abdominal organs, although still attached, are displaced outside the body. AFP is produced in the fetal liver, and during normal pregnancy a very small amount reaches the maternal blood. After 15 weeks' gestation the level is sufficient for AFP to be a strong marker.
If the AFP level exceeds 2. In recent years a new screening method has been developed that does not use markers. Instead cell-free cf DNA is tested in a maternal blood sample. As with marker screening most affected pregnancies have a positive test result but some unaffected pregnancies are also positive. These are either rare or have variable severity. This is more likely to occur in women who are over-weight or when the blood sample is taken early in pregnancy.
All of them are more expensive than marker screening. It will be offered only to women when are at high risk based largely on marker screening results.
FXS is the most common inherited cause of severe learning disability although most cases occur in families with no history of the syndrome. In general, FXS is the second most common cause of learning disabilities, after Down's syndrome.
Boys have learning difficulties ranging from mild to severe intellectual impairment. Girls can have normal intelligence but a large proportion have learning difficulties comparable with affected boys.
Common behavioural features in boys with FXS include short attention span, distractability, impulsiveness, and overactivity. Girls with FXS, including those without learning difficulties, may have concentration problems and social, emotional and communication difficulties related to extreme shyness and anxiety in social situations.
Many affected individuals exhibit autistic-like features: a dislike of eye contact, difficulty in relating to other people, anxiety in social situations, insistence on familiar routines and hand flapping or biting.
Speech and language is usually delayed, with continuing speech difficulties. At a particular point on the X chromosome there is normally a block of between 11 and 54 copies of a small DNA sequence.
FXS results from a fault at this point where the block is abnormally extended to over copies. This is called a full mutation FM. The block is so long that it interferes with the production of an important protein. Since boys only have one X chromosome, those with an FM are severely affected. Girls have two X chromosomes and if one of produce sufficient protein. An FM in a child always comes from the mother never the father , who has a larger than normal block of DNA. Usually the mother has a moderately extended block with copies called a pre-mutation PM.
This is harmless to the mother, being insufficient to alter her protein production, but it becomes unstable at the time of conception when it might expand to an FM in the fetus. The chance of a maternal PM being passed to the fetus and expanded into an FM varies according to the number of copies. For example, a PM with 65 copies has a 1 in 40 chance whilst a PM with 90 copies has a 1 in 3 chance. Occasionally, the mother of a child with an FM is not a PM carrier, and is one of those females who has an FM but is an unaffected carrier of the disorder.
An FM mother will pass the FM to the child in half her pregnancies. About one in pregnant women is a PM carrier and 1 in women is an unaffected FM carrier. These proportions do not vary according to maternal age or ethnic origin.
Most babies with FXS are born to women who do not have a family history of the disorder. Therefore, screening is needed to determine any woman's PM or FM carrier status. Screening can be carried out on a woman's sample antenatally or pre-pregnancy. This is much simpler than with Down's syndrome screening. DNA is extracted from a blood sample and the number of copies is measured.
If a PM or FM is detected, the result is classified as screen positive, otherwise screen negative. From the number of copies in the PM, the chance of expansion to an FM fetus is calculated. Unlike the other screening tests the diagnostic tests available to those with screen positive results is not necessarily definitive in all cases.
The diagnostic test is to see if the fetus has inherited the mutated X chromosome and the block has expanded to an FM. However, there is no way of distinguishing those female FM fetuses who have FXS with its associated intellectual and behavioural difficulties from those who will not go on to exhibit these traits.
This does not seem to be a major problem for most couples as studies show that termination of pregnancy is the chosen option for nearly all those with FM fetuses. All genes, apart from those on the X and Y chromosomes in males, come in pairs. SMA and CF have a similar pattern of inheritance, each occurring when both genes in a specific pair are faulty. This leads to loss of production of an important chemical. The parents are carriers with only one faulty gene and so are healthy.
Children receive one gene of a pair from each parent. Most babies with these disorders are born to couples, neither of whom has a family history of the disorder. Therefore, screening is needed to determine any couple's carrier status. Screening can be carried out either antenatally or pre-pregnancy in couples or single individuals.
The best method is a 'paired sequential' approach. The Cystic Fibrosis Trust offers information about the causes, symptoms and treatments of CF along with details about day to day living with Cystic Fibrosis. Helpline: NHS Choices gives full information on the checks and tests offered in pregnancy.
Healthtalkonline offers shared experiences, videos and stories from 37 women and 8 couples from the UK. Topics include making decisions about screening, including those that have and have not ended the pregnancy. ARC Tests explained. Payne J. When it comes to content, our aim is simple: every parent should have access to information they can trust. All of our articles have been thoroughly researched and are based on the latest evidence from reputable and robust sources.
We create our articles with NCT antenatal teachers, postnatal leaders and breastfeeding counsellors, as well as academics and representatives from relevant organisations and charities. Read more about our editorial review process. Antenatal screening in pregnancy. Read time 10 minutes. Breadcrumb Home Pregnancy Tests, scans and antenatal checks Antenatal screening in pregnancy. Email Post Tweet Post.
Available foetal and pregnancy screening tests There are a number of foetal screening tests that are offered as part of your antenatal care. The anomaly scan All pregnant women are offered the opportunity to have an anomaly scan between 18 and 21 weeks. Screening for sickle cell and thalassaemia All pregnant women will be asked questions about their family origins to see if they should be offered a blood test to screen for sickle cell disorder and thalassaemia. Cystic fibrosis Cystic fibrosis affects the internal organs, especially the lungs, pancreas and digestive system, by clogging them with thick sticky mucus.
What is chorionic villus sampling CVS? What is amniocentesis? Last updated: May Further information Our support line offers practical and emotional support in all areas of pregnancy, birth and early parenthood: Show references.
Information you can trust from NCT When it comes to content, our aim is simple: every parent should have access to information they can trust.
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