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Prenatal Screening

The Pros and Cons of Enhanced AFP
By Tamar Weiss

"I decided I wanted to know everything I could about my pregnancy and the baby I was carrying," says Leelah Gitler. "If something was wrong with my baby, I wanted to know about it, prepare myself for it and find out my options."

Pregnant women today have more options and health benefits than their mothers may have ever dreamed about. Women can now note detailed progress of their pregnancies with extreme accuracy and discover possible disorders that the fetus might have while in its earliest weeks of gestation. Conditions once seen as hopeless are now treatable with early detection.

Yet along with all of the benefits that modern medicine and genetics allow patients comes the necessity to make weighty decisions that can be frightening and disquieting.

What is Enhanced AFP?
One of the choices today's pregnant women must make is whether to have an enhanced alfa fetoprotein (XAFP) screening. The XAFP is a test performed generally in weeks 16 to 18 of pregnancy, and it determines the level of risk that the expectant mother is carrying a fetus with disorders such as Down syndrome (trisomy 21), open neural tube defects such as spina bifida and anencephaly, abdominal wall defects (omphalocele, gastroschisis) and Edwards syndrome (trisomy 18).

False Positives
"Enhanced AFP testing can only indicate risk of an abnormality," says Dr. Jacob Canick of the AFP lab at Women and Infants Hospital of Rhode Island. "It cannot tell you with certainty that you do or do not have an affected fetus."

For this reason, many women decline to have the procedure done. Because the screening indicates the risk that a woman may be carrying an affected fetus, the results may often suggest that there is a relatively high risk while the mother is carrying a perfectly normal fetus. Some women prefer not to go through the distressful and agitating period of receiving a high-risk result and waiting to take whatever follow-up test may be suggested to obtain a clearer indication, only to learn that the baby is perfectly healthy.

"I relied on the advice of friends and family members who had been through the experience," says Carmen Hickerson of Louisville, Ky. Carmen's sister and close friend advised her against taking the test because of the great number of "false positive" results, and that such results may lead to an unnecessary amniocentesis (the Centers for Disease Control and Prevention report that the rate of miscarriage after amniocentesis is between 1 in 200 and 1 in 400). In addition, aborting the fetus "was never something I would consider," Hickerson says. She felt the test would be unnecessary for her even if she had found out that her fetus was affected.

Because the AFP is only a screening test, "you have to expect many false positives," says Dr. Ronald Bachman, chief of Kaiser Permanente's Department of Genetics in Oakland, Calif. "One needs good genetic counseling. One also needs a good genetic center to do appropriate follow-up of all positives. This involves, in addition to genetic counseling, good ultrasound and the availability of amniocentesis by experienced perinatologists or obstetricians."

Laura Major, having done the AFP, found that she was at great risk for carrying a fetus with Down syndrome. "Our genetic counselor advised that I do an amniocentesis as a follow-up test," Major says. "It turned out that my baby was healthy, and I was so thankful when I got those results, but finding out my results from the AFP and the idea of having an amnio that put my baby at risk were so frightening. I really don't know whether I would choose to do the AFP again."

Leelah Gitler saw her opportunity to take the XAFP as one that would help her realize if she was at risk for having a baby with certain conditions. "I wanted to know what to do if I were faced with a problem, if my baby were to be born with a serious birth defect or other condition," she says.

Though receiving positive screening results can be painful and worrisome, the guidance of a genetic counselor will help clarify your actual chance of having a baby with a problem, says Carol Norem, a genetic counselor with Kaiser Permanente. "We work with individuals and families who have, or are at risk for, genetic disorders and/or birth defects by educating, supporting and helping them understand information regarding these conditions, the possible testing options and the often difficult decisions they face," Norem says.

If Your Test Is Positive
If a problem is actually detected with further testing, counselors also can help in the next step. "We discuss the options of continuing the pregnancy, ending the pregnancy or continuing the pregnancy and placing the child up for adoption," Norem says.

For couples who plan to continue pregnancy with an affected fetus, the XAFP – and follow-up test if necessary – can provide time to prepare for what lies ahead. Couples may want to begin psychological counseling in order to come to terms with the difficulties they face and prepare for medical care for the immediate postpartum time.

Before this type of screening test was invented, the risk of carrying fetuses affected with certain conditions was based on maternal age alone. The AFP gives a more accurate appraisal. "It is the goal of those of us in research to reduce the number of false positives these tests generate," Dr. Canick says.

It remains that the choice to undergo the XAFP is a consequential one, laden with pros and cons. "And I feel equally strongly that it is the right of the patient to accept or refuse such tests."

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About the Author: Tamar Weiss is a freelance writer.



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