They can also help you make a decision, if needed, about whether to continue with your pregnancy. In some cases, you may be referred to a genetic counsellor a healthcare professional trained in genetics.
They will discuss your risk of passing on certain genetic conditions and can offer you advice about what to do when you get the results of CVS. The test takes about 5 minutes, although the whole consultation will take about 30 minutes. CVS has been described as uncomfortable rather than painful, and there may be some cramps afterwards which are similar to menstrual cramps. Early in pregnancy, the embryo divides into 2 parts.
One part develops into the baby; the other part develops into the placenta. The chorionic villi are formed when the fertilised egg divides, which means they have exactly the same DNA as the embryo, including any possible genetic abnormality. Any defect in the chorionic villi will also be present in the fetus. CVS increases the risk of miscarriage, but only 1 in every pregnancies that end in miscarriage would be directly due to CVS.
It is important to discuss your risk of miscarriage with your doctor, midwife or genetic counsellor. The specific figure for the risk of a miscarriage depends on the experience of the doctor doing the test and the difficulty he or she has in obtaining the sample. It is therefore important that a CVS test is only carried out by a doctor experienced in this technique and it should be done after the 11th week of pregnancy.
You may have some vaginal bleeding after a CVS. Talk to your doctor about what you can expect after the testing and what symptoms to look out for. After CVS has been carried out, the sample of chorionic villi will be taken to a laboratory so that the cells can be examined under a microscope. The number of chromosomes in the cells can be counted, and the structure of the chromosomes can be checked for any abnormalities.
If the CVS is being carried out to test for a specific genetic disorder, the cells in the sample can also be tested for this. CVS is estimated to be about accurate in 99 cases out of However, it cannot test for every birth defect, and it may not give conclusive results.
In about 1 in every cases, the results of CVS cannot be completely certain that the chromosomes in the fetus are normal. If this happens, it may be necessary to have further tests, such as examining the chromosomes in cells from the parents. It may also be necessary to have amniocentesis an alternative test in which a sample of amniotic fluid is taken from the mother to confirm a diagnosis.
Prenatal genetic services: toward a national data base. Clin Obstet Gynecol ; The safety and efficacy of chorionic villus sampling for early prenatal diagnosis of cytogenetic abnormalities. N Engl J Med ; Risk evaluation of CVS. Prenat Diagn ; Abramsky L, Rodeck CH. Women's choices for fetal chromosome analysis.
Effect of chorionic villus sampling on utilization of prenatal diagnosis in women of advanced maternal age. Clin Genet ; Am J Hum Genet ;53 Suppl 3 A randomized comparison of transcervical and transabdominal chorionic-villus sampling.
Human cytogenetics: a current overview. Am J Dis Child ; Burke BM, Kolker A. Clients undergoing chorionic villus sampling versus amniocentesis: contrasting attitudes toward pregnancy. Health Care Women Int ;14 2 Morbidity and mortality of abortion in the United States. In: Hodgson JE, ed. Abortion and sterilization: medical and social aspects. London: Academic Press Inc. Abortion mortality, United States, through Am J Obstet Gynecol ; Schemmer G, Johnson A.
Genetic amniocentesis and chorionic villus sampling. Obstet Gynecol Clin North Am ; Risk evaluation of chorionic villus sampling CVS : report on a meeting.
Vascular pathogenesis of transverse limb reduction defects. J Pediatr ; Severe limb abnormalities after chorionic villus sampling at days' gestation. Lancet ; Pediatrics ; Analysis of limb reduction defects in babies exposed to chorionic villus sampling.
Teratology ; Cook obstetrics and gynecology catheter multicenter chorionic villus sampling trial: comparison of birth defects with expected rates. Am J Obstet Gynecol ; Terminal transverse limb defects and early chorionic villus sampling: evaluation of 4, cases with completed follow-up. Am J Med Genet ; Prenat Diag ;12 suppl :S Chorionic villus sampling: experience with cases performed by a single operator.
Obstet Gynecol ; Distal limb deficiency following chorionic villus sampling? Transverse limb reduction defects after chorion villus sampling: a retrospective cohort study. Randomised comparison of amniocentesis and transabdominal and transcervical chorionic villus sampling. Limb deficiencies, chorion villus sampling, and advanced maternal age. Medical Research Council European Trial of chorion villus sampling.
Congenital malformations subsequent to chorionic villus sampling: outcome analysis of consecutive procedures. Froster UG, Jackson L. Increased risk for transverse digital deficiency after chorionic villus sampling: results of the United States Multistate Case-Control Study, Mastroiacovo P, Botto LD. Chorionic villus sampling and transverse limb deficiencies: maternal age is not a confounder.
Am J Med Gen ; Amniocentesis or chorionic villus sampling for prenatal genetic testing: a decision analysis. J Clin Epidemiol ; Chorionic villus sampling utilization following reports of a possible association with fetal limb defects.
TABLE 1. Gruppo Italiano Diagnosi Embrio-Fetali. TABLE 2. Retabulated from original publication L. Holmes, personal communication. TABLE 3. During pregnancy, the placenta provides oxygen and nutrients to the growing baby and removes waste products from the baby's blood. The chorionic villi are wispy projections of placental tissue that share the baby's genetic makeup.
The test can be done as early as 10 weeks of pregnancy. Chorionic villus sampling can reveal whether a baby has a chromosomal condition, such as Down syndrome, as well as other genetic conditions, such as cystic fibrosis. Although chorionic villus sampling can provide valuable information about your baby's health, it's important to understand the risks — and be prepared for the results. Chorionic villus sampling can provide information about your baby's genetic makeup.
Generally, chorionic villus sampling is offered when the test results might have a significant impact on the management of the pregnancy or your desire to continue the pregnancy. Chorionic villus sampling is usually done between weeks 11 and 14 of pregnancy — earlier than other prenatal diagnostic tests, such as amniocentesis. Chorionic villus sampling can't detect certain birth defects, such as neural tube defects.
If neural tube defects are a concern, an ultrasound or genetic amniocentesis might be recommended instead. Your health care provider might caution against transcervical chorionic villus sampling — which is done through the vagina — if you have:. Rarely, your health care provider might caution against transabdominal chorionic villus sampling — which is done through the abdominal wall — if:. Rh sensitization. Chorionic villus sampling might cause some of the baby's blood cells to enter your bloodstream.
If you have Rh negative blood and you haven't developed antibodies to Rh positive blood, you'll be given an injection of a blood product called Rh immune globulin after chorionic villus sampling. This will prevent your body from producing Rh antibodies that can cross the placenta and damage the baby's red blood cells. A blood test can detect if you've begun to produce antibodies.
Some older studies suggested that chorionic villus sampling might cause defects in a baby's fingers or toes. Try ObGFirst Free! Sign In. Lost your password? Password Trouble?
ObGFirst Free Trial. Disclaimer Participants have an implied responsibility to use the newly acquired information to enhance patient outcomes and their own professional development.
0コメント