Chorionic Villus Sampling is an alternative to amniocentesis. At some point it will probably replace amniocentesis completely.
This test must be done between the 9th and 11th weeks. A catheter is inserted through the cervix and a small amount of chorionic villi tissue is sucked into the catheter by a syringe at the other end. Chorionic villi is tissue that will develop into the placenta. The entire procedure is monitored by ultrasound. The results of the test can be obtained in 2 to 4 days. However, the risk of miscarriage is slightly higher than amniocentesis, 3 out of every 200 procedures.(1)
Possible problems include damage to the embryo, miscarriage, cervical lacerations, hemorrhage, and infection. Women who are DES daughters or other women at risk for cervical abnormalities should be aware of the risks of having instruments forced through the cervix, a possible cause of loose (incompetent) cervix later in pregnancy. CVS is contraindicated in cases of vaginal infection, Rh sensitization, multiple gestation, or a markedly retroflexed uterus. Rh negative women risk mixing of the maternal and fetal blood supply. (1)
Beginning in 1991, there were reports of infants born with serious limb deficiencies, and sometimes other birth defects (hemangiomas and cranial nerve palsies), who had been exposed to the CVS procedure. There is now an organization called The Chorionic Villus Sampling Birth Defects Registry, hosted by Harvard University, and this group of people is collecting information from those who have had children born with birth defects who were exposed to this sampling procedure. They hope to learn more about the nature of the effects of Chorionic Villus Sampling. The World Health Organization also maintains an International Registry of CVS procedures.
Population-based studies seem to indicate a rate of 5-6 cases of malformations per 10,000 live births (2). (What about those that weren't born live, but still had this defect? That would make the rate higher.) The rate of malformation is higher when the gestational age is lower. This makes being sure of your dates absolutely imperative. The risk is greatest when done at less than 10 weeks gestation, and this can involve limb malformation, missing fingers and toes, and malformation of the the mouth and jaw. When done at greater than 10 weeks gestation, malformations seem to be confined to fingers and toes, but this is no consolation. So your baby will be missing just a finger or toe instead of a leg. Does that make it OK?
Amniocentesis and Chorionic Villus Sampling are only offered to women who are:
1. Over 35 years of age, to test for spina bifida and Down's Syndrome.
2. Women with history of birth defects in previous pregnancies or family history.
The only reason these tests are offered is so that they can then offer you an abortion to terminate the pregnancy. This is the only reason to offer these tests, because there is little or nothing that can be done about these conditions in-utero.
By the way, 80% of down syndrome babies are born to women under 35 years of age!
1. Taken from "Understanding Lab Work in the Childbearing Year" 4th Edition, by Anne Frye, 1990.
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