Other family history. Couples without a previously affected child also may be offered prenatal testing if their family medical histories indicate their children may be at increased risk of inheriting a genetic disorder. Prenatal testing would be offered only if the suspected condition can be diagnosed prenatally. Prenatal diagnosis is possible for all common chromosomal disorders, but not all genetic ones. CVS cannot diagnose these disorders.
Referral elsewhere is an option.
In these cases, amniocentesis may be offered as an alternative prenatal test. CVS requires taking a small piece of the chorionic villi, which are wisps of tissue that attach the pregnancy sac to the wall of the uterus. The laboratory will analyze the cells from the villi, which normally have the same genetic and biochemical makeup as the embryo. Tests results are generally available in about 10 days, though preliminary results may be available sooner. First, the vagina and cervix are thoroughly cleansed with an antiseptic.