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Chorionic villi sampling: a wolf in sheep's clothing?

It used to be that amniocentesis--a prenatal test where a sample of the amniotic fluid that surrounds the fetus is removed and analyzed--was the only tried-and-true standard of care for detecting abnormalities in fetal development.

In the 1960s and 1970s, though, researchers found that the placenta could be biopsied, allowing doctors to conduct genetic analysis earlier in pregnancy than they could with amniocentesis--as early as 8 weeks' gestation rather than 15 or 18 weeks'. The procedure, chorionic villi sampling (CVS), has been used in the past 10 years at prenatal diagnostic centers, including hospitals, outpatient clinics and obstetricians' offices.

In the late 1980s and early 1990s, there was just a hint of concern in the medical and scientific communities about the safety of chorionic villi sampling. It wasn't until March 1991, after a study linked CVS and birth defects, specifically, limb deficiencies and limb-reduction defects, that those communities sat up and took notice.

"The only advantage of CVS over amniocentesis is that it allows a couple to know earlier in the pregnancy that there is an abnormality, affording them the option of undergoing a first-trimester abortion rather than a later abortion," said Stephanie O'Connor, cochair of an ATLA litigation group on CVS.

In performing CVS, a sample of chorionic villi--the tiny, fingerlike projections of the placenta through which the mother and baby exchange nutrients, gases, and fetal wastes--is extracted with a catheter that is inserted into the mother's cervix. With a method used less frequently, a needle is inserted into the abdomen. Genetic analysis of the sample reveals whether the fetus has chromosomal abnormalities such as Down's syndrome, Tay-Sachs disease, and cystic fibrosis. The analysis does not detect neural tube defects like spina bifida, so expectant mothers who opt for CVS may also have to undergo amniocentesis.

In some instances, chorionic villi sampling may do more harm than good. "The procedure may cause a vascular disruption--an interruption in the flow of blood to the fetus--at a critical point in embryological development. This occurs when the [fetus's] limbs, tongue, jaw, and skin are forming," O'Connor said. Common deformities include shortened limbs, fingers, and toes; missing limbs, fingers, and toes; smaller than average tongue and jaw; and hemangiomas, or strawberry birthmarks.

Caroline McGuirk, project coordinator of the Chorionic Villus Sampling Birth Defects Registry at Massachusetts General Hospital in Boston, said, "Many women have CVS, and many of their children do not have birth defects. Some babies are born with birth defects for unknown reasons. We are not saying that just because a child was exposed to CVS he or she will have a birth defect." The registry (accessible on the Internet at http://neuro-www3. was set up to study whether malformations in CVS-exposed children are distinctive compared to similar ones in unexposed children.

"Many physicians try to reassure their patients of the safety of CVS by telling them that the birth defects that were seen in the early 1990s were the result of performing the procedure too early in the pregnancy. Some tell their patients that the facility where the procedure will take place has had no reported incidences of birth defects that resulted from extracting chorionic villi. These statements can be misleading to couples contemplating the procedure," said O'Connor, a New York City lawyer who represents plaintiffs in chorionic villi sampling cases.

The Centers for Disease Control and Prevention has reported that the risk for defects is greatest when the sampling is done at or before nine weeks' gestation, but it has also cautioned that the procedure can cause abnormalities when performed later in pregnancy. In 1995, the agency recommended specific guidelines for counseling prospective parents considering CVS.

The guidelines include informing parents of their risk of transmitting genetic abnormalities based on maternal age, race, and family history (that is, letting parents know whether the procedure is recommended); making parents aware of the limitations of CVS in detecting abnormalities; telling parents about potential serious complications of the procedure, such as the risk for miscarriage and limb deficiencies; and informing parents that the timing of the procedure is crucial to avoid putting the mother's health at risk with a late-term abortion. (Richard S. Olney et al., Centers for Disease Control and Prevention, Chorionic Villus Sampling and Amniocentesis: Recommendations for Prenatal Counseling, 44 Morbidity & Mortality Wkly. Rep. 1 (1995).)

Taking the case

Although the adverse effects of this procedure have been known for at least a decade, litigation involving CVS is still in its early stages.

"This is not formula litigation," said Steven Jay Bassin, who practices law with O'Connor in New York City and who co-chairs the CVS litigation group. "The learned intermediary doctrine comes up in some cases. Federal preemption motions are often filed. Other cases are more garden variety and involve products liability, medical negligence, or lack of informed consent."

According to O'Connor, defendants typically include the hospital where the procedure was performed, the genetics counselor who discussed CVS with the prospective parents, the physician who performed the procedure, and the catheter manufacturer.

"Cases against hospitals are twofold," O'Connor said. "The hospital may be liable because it provides the equipment and the facility where the procedure took place, and it also employs the genetic counselor who was responsible for informing the parents of risks of chorionic villi sampling."

Where the lawsuit names the genetic counselor, the issue of informed consent comes into play. "The primary issue raised in these cases is the right of pregnant women to be made aware of the risks and dangers inherent in prenatal testing," O'Connor said.

Some hospitals dispute plaintiffs' claims that the counselor is at fault, saying that the plaintiffs' conduct is culpable. "The hospital claims the counselor informed the parents of the risks and that now the parents are saying in hindsight that they would not have gone ahead with the procedure had they known what the outcome would be," said O'Connor. As a result, the dispute usually focuses on what was said during the counseling sessions.

For example, in the case of Horowitz v. Cook Ob/Gyn, the plaintiff claimed that the genetic counselor discussed only the risk of miscarriage and not the procedure's potential for causing birth defects. (No. 95L-02803 (Ill., Cook County Cir. Ct. settled Nov. 8, 1999).)

The physician may be held responsible for neglecting to obtain the patient's informed consent. He or she may also be liable for performing the procedure despite being aware of its risks. "A common defense in cases where the procedure was performed before March 1991 is the so-called state-of-the-art defense. The medical community claims it was unaware of the risks of limb defects," O'Connor said. She refutes this defense by pointing to a number of reports published in the 1980s that associate limb reduction defects with CVS.

For example, in Prenatal Tests, published in 1988, the author, Robin J.R. Blatt, cautions expectant mothers that "CVS has been implicated in the cause of disabilities such as limb deficiencies.... Other complications of CVS include rupture of the amniotic sac, causing a spontaneous abortion or a miscarriage."

The physician may also be held liable for misusing the catheter, which is subject to regulation by the FDA. Other possible theories of liability include a doctor's using a recycled catheter, his or her using a catheter manufactured outside the United States that has not gained approval for use in this country, and a doctor's using a catheter he or she fashioned rather than one intended for extracting chorionic villi.

If plaintiffs file suit against the catheter manufacturer, "the manufacturer often tries to pin the liability on the physician who performed the procedure, claiming product misuse," O'Connor said. "FDA-approved catheters carry a specific statement in the labeling that the procedure should not be performed under 10 weeks' gestation or 70 days of pregnancy."

According to O'Connor, the catheter manufacturer may still be held liable. "It is my belief, and the medical literature would support me, that limb reduction defects due to CVS, though rare, are a potential risk at any point in the pregnancy. I have been involved in at least two cases where it was performed at 10 1/2 and 11 weeks of pregnancy" and the fetus then developed abnormally.

A little knowledge is a dangerous thing, and that may be especially so when expectant parents struggle to decide whether to undergo chorionic villi sampling early in pregnancy--and perhaps put a healthy fetus at risk---or to wait a few weeks to have the safer prenatal exam, amniocentesis.

"Although CVS is still being offered to women as a comparatively safe alternative to amniocentesis, it is being performed less frequently than it was before and certainly less frequently than in the heyday of the late 1980s and early 1990s," O'Connor said. "This may well be due to the fact that when women are properly counseled about the risks and benefits of CVS, many choose to wait and do amniocentesis, a procedure with a proven track record of safety over many years."
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Author:Reichert, Jennifer L.
Geographic Code:1USA
Date:Feb 1, 2000
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