The results should be available within three working days. If all the chromosomes have to be looked at, it can take up to three weeks. Amniocentesis has a 0. At most, one test in will result in pregnancy loss. When deciding whether to go ahead with this test, try to balance the risk of miscarriage against the value of the result to you.
Your midwife or doctor will explain what is involved and you will usually be offered counselling. Your midwife or doctor will make sure you see the appropriate health professionals to help you get all the information and support you need so you can make the choices that are right for you and your family. We will not reply to your feedback. Don't include any personal or financial information, for example National Insurance, credit card numbers, or phone numbers.
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Contacts for common benefits are listed below. Call Email dcs. Genet Med. Epub Jul Other chapters in Help Me Understand Genetics. Genetics Home Reference has merged with MedlinePlus. Learn more. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. What is noninvasive prenatal testing NIPT and what disorders can it screen for?
From Genetics Home Reference. Scientific journal articles for further reading Committee Opinion No. Skrzypek H, Hui L. Noninvasive prenatal testing for fetal aneuploidy and single gene disorders. Epub Feb Topics in the Genetic Testing chapter What is genetic testing? What are the different types of genetic tests? Second trimester maternal serum screening also looks at the chance of your baby having a neural tube defect like spina bifida.
This is because the chance of having a baby with Down syndrome and certain other chromosomal conditions increases as you get older. For Down syndrome, at:. There are several things to think about before having antenatal tests. For example, how do you feel about what you might find out from these tests? What will you do if you get a high-risk result from a screening test? Would you go on to take a diagnostic test? Your doctor or midwife will let you know the results of screening tests.
If you get high-risk results, the doctor or midwife will talk with you about diagnostic tests. Diagnostic tests involve taking small samples of tissue from your placenta or fluid from around your baby.
There are two ways to take the samples — chorionic villus sampling CVS and amniocentesis. First, a doctor gives you a local anaesthetic for your tummy area. Next, the doctor uses ultrasound to guide a thin needle into your uterus to collect one or more samples. CVS is best done at weeks of pregnancy — that is, in the first trimester.
It might be up to two weeks until you get CVS results. To those women with a very high risk for all type of aneuploidy e. To all other women, the result of the combined test could be used for counseling, giving them the choice of selecting either:.
An option for this approach is depicted in Figure 1. Non-invasive prenatal testing may be best used in a contingent approach. In the example, combined first trimester screening is offered to all women as an initial screening tool. From this, women are stratified by risk to determine further management.
Women with a high risk are offered an invasive test chorionic villus sampling or amniocentesis. Women with a low risk are reassured and advised that no further testing is needed. Women with an intermediate level of risk are offered a non-invasive prenatal test. A discussion of the risks, benefits, and alternatives of various methods of prenatal screening and diagnostic testing, including the option of no testing, should occur with all patients.
Given the performance of conventional screening methods, the limitations of cell-free DNA screening performance, and the limited data on cost-effectiveness in the low-risk obstetric population, conventional screening methods remain the most appropriate choice for first-line screening for most women in the general obstetric population.
The cell-free DNA test will screen for only the common trisomies and, if requested, sex chromosome composition. Given the potential for inaccurate results and to understand the type of trisomy for recurrence-risk counseling, a diagnostic test should be recommended for a patient who has a positive cell-free DNA test result.
If a fetal structural anomaly is identified on ultrasound examination, diagnostic testing should be offered rather than cell-free DNA screening. Patients should be counseled that a negative cell-free DNA test result does not ensure an unaffected pregnancy. National Center for Biotechnology Information , U. Demetrios Rizos. Author information Copyright and License information Disclaimer.
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