communicating risk in prenatal genetic testing
TRANSCRIPT
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Communicating Risk in Prenatal Genetic TestingElena A. Gates, MD
Prenatal testing for Down syndrome and neural tube defects has become routine, and testing for other geneticconditions is becoming commonplace. Counseling about these tests involves a discussion of riskinformation, so pregnant women and their partners can use the information effectively when they makechoices about testing. Discussing risk can be challenging, as many individuals, particularly those of lowerliteracy, have a poor understanding of the numerical concept of risk. Furthermore, whether risk iscomprehended accurately or not, it is interpreted by patients in light of their existing knowledge and pastexperiences. Strategies available to optimize understanding of risk include communication of risk figures asfrequencies rather than as probabilities or percentages and explicit discussion of a woman’s preconceptionsabout her risk and about the condition being tested for. J Midwifery Womens Health 2004;49:220–227© 2004 by the American College of Nurse-Midwives.
keywords: risk, prenatal genetic testing, genetic counselingaw
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NTRODUCTION
renatal care in the United States now routinely includes anffer of testing for chromosomal disorders and otherenetic conditions. The process of offering these tests is not
simple one. An ethical approach to prenatal testingncludes the provision of adequate factual information asell as the support women and their partners need to make
esting decisions that are both informed and autonomous.1
lthough careful consideration of the personal impact ofhe testing process and of the potential outcomes of testings essential to a good decision, accurate and understandablenformation about risks is critical as well. This includes theisk of having an infant with the condition in question andhe risks associated with the testing procedure. A clearernderstanding of the alternative methods of communicatingisk and of the means by which women comprehend andssess risk will enhance the ability of clinicians to ade-uately inform and counsel their patients about the optionsvailable for prenatal diagnostic testing.
Consideration of risk is fundamental to decision makingbout the use of prenatal genetic testing. National practicetandards, as articulated by the American College of Ob-tetricians and Gynecologists (ACOG), include offering allregnant women screening for Down syndrome, trisomy8, and neural tube defects regardless of age.2 Screeningest results typically provide a personalized risk estimate,ased on factors including maternal age, nuchal translu-ency measurement, and levels of analytes such as alpha-etoprotein, estriol, beta-hCG, and pregnancy-associatedlasma protein A. For example, a 30-year-old woman,hose age-related risk for a Down syndrome birth is
pproximately 1/900 (1.1/1,000), may learn that her ad-usted risk after screening is 1/1,500 (0.6/1,000), or she maye told that her risk is elevated at, for example, 1/5020/1,000). She will then need to mentally compare her
ddress correspondence to Elena A. Gates, MD, University of California, Sanrancisco, 2356 Sutter Street, 3rd Floor, San Francisco, CA 94115. E-mail:
202004 by the American College of Nurse-Midwives
ssued by Elsevier Inc.
djusted risk with her age-related risk before decidinghether to consider her results “reassuring.”Advances in understanding the human genome and in
dentification of the genetic errors responsible for diseases,uch as cystic fibrosis (CF), are leading to an expansion inhe number of conditions for which pregnant women andheir partners will need to consider testing. As of 2001, theCOG and the American Society for Human Genetics
ecommend “offering CF screening to couples in whom oner both partners are Caucasian and are planning pregnancyr seeking prenatal care. . . . It is further recommended thatcreening should be made available to couples in otheracial and ethnic groups who are at lower risk and in whomhe test may be less sensitive.”3 One in 30 Northernuropean Caucasians carries a CF mutation, yielding a ratef 1/3,000 affected births for a couple who are both fromhis ethnic group. Tay Sachs disease, sickle cell anemia,nd hemoglobinopathies are other conditions for whichreconception and prenatal testing is routinely offeredrimarily on the basis of the ethnicity of the woman and herartner. Therefore, it is safe to say that all pregnant womenn this country will encounter conversations and testingecisions that require an understanding and assessment ofisk.
A 37-year-old woman, who routinely would be offered ahoice between screening and diagnostic testing for chro-osomal abnormalities, will have to weigh several risks inaking a decision about which, if any, test to take4–8
Table 1). Information about other inherited diseases willlso need to be discussed. In some communities, trainedenetic counselors are available to pregnant woman, espe-ially those at higher risk of fetal chromosomal abnormal-ties. Unfortunately, the supply of genetics counselors isnadequate to current need, so in many cases, counselingegarding testing must be provided by obstetricians, mid-ives, or family practitioners.9 These individuals will need
o acquire the skills necessary to provide an adequate levelf counseling about common conditions and routinely usedesting strategies. The growing number of conditions for
hich testing is available and the expanding options forVolume 49, No. 3, May/June 20041526-9523/04/$30.00 • doi:10.1016/j.jmwh.2004.02.014
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creening and diagnostic testing complicate the counselingrocess. Recent assessments indicate that women undergo-ng prenatal genetic testing are frequently poorly informed,egardless of their literacy level.10,11 One survey in thenited Kingdom noted that only 54% of women thought
hat they had exercised informed choice during their ma-ernity care.12 Busy obstetric providers struggle to provideoth factual information as well as counseling about test-ng. Ensuring an adequate understanding of risk informa-ion is particularly challenging.
OW DO WOMEN UNDERSTAND RISK IN THE CONTEXT OFENETIC TESTING?
he risk information provided to obstetric patients isenerally given in a numerical format. Indications are thatatients, in general, lack the numerical skills needed for andequate understanding of the risk information with whichhey are presented. The fact that risk is usually presented asdds or probabilities in the context of prenatal testingakes adequate comprehension even more of a challenge.13
isks may be perceived as higher when presented as oddsather than as percentages.14,15 Furthermore, proportionsan be confusing, particularly when denominators arearger. As Walker points out, “to many, 1/400 soundsigher than 1/200 because the denominator is bigger. Tony of us, 1/20 may sound higher than 5%, or vice versa.”16
he quantitative information provided to patients will onlye useful if those patients have “some facility with basicrobability and numerical concepts, a construct calledumeracy.”17 One sees repeated indications that women ofower literacy and, in particular, numeracy, have the mostifficulty in accurately interpreting information aboutisk.17–19
Schwartz assessed numeracy by using three questionsmong a group of 500 female veterans.17 First, subjects
lena A. Gates, MD, is Professor of Clinical Obstetrics, Gynecology, andeproductive Sciences and Director of the Division of General Gynecology at
he University of California, San Francisco. She has been involved nationallyn projects aimed at enhancing patient decision making about prenatal genetic
Table 1. Risk Figures to Be Considered by a 37-Year-Old Woman
Age-related risk of chromosomal abnormality at midtrimesterAge-related risk of chromosomal abnormality at deliveryAge-related risk of Down syndrome at midtrimesterAge-related risk of Down syndrome at deliveryExpanded alpha-fetoprotein risk definition for “screen positive” (state of CaRisk of pregnancy loss due to chronic villus sampling (CVS)Risk of pregnancy loss due to amniocentesisNuchal translucency risk definition for “screen positive”
Adapted from ACOG, 200230; Cuckle HA, 198731; Hook EB, 198132; Hook EB, 198333;
cesting.
ournal of Midwifery & Women’s Health • www.jmwh.org
ere asked how many times a coin will come up heads if its flipped 1,000 times. Second, they were asked to convertnumber problem from a percentage, 1%, to a proportion,0/1,000. Third, subjects were asked to convert a propor-ion, 10/1,000, to 1%. Only 54% correctly responded to theoin-flip question. Fifty-four percent could correctly con-ert 1% to 10/1,000, but only 20% could convert 10/1,000o 1%. Almost one third of the women had no correctesponses. The majority of the women (64%) were highchool graduates; 36% had more than a high schoolducation. Subjects’ ability to use numeric risk informationo understand the level of risk reduction associated withcreening mammography was directly related to their suc-ess at answering the numeracy questions. Even those whoere able to answer all three numeracy questions correctly
ssessed the risk reduction offered them by mammographynly 40% of the time.17 Chase interviewed women prior toheir participation in prenatal genetic counseling to assessheir ability to understand risk.18 A risk of a serious birthefect was described either as a risk of 4 per 100 or a riskf 40 per 1,000. Risk descriptions were randomly assigned.omen frequently made errors in identifying the percent-
ge equivalent for 1 per 1,000. Although 75% correctlydentified 4/100 as 4%, only 41% identified 40/1,000 as 4%.
ore than 25% of participants could not correctly identify/1,000 as less than 1%. As expected, those with lowerducational attainment had more difficulty than collegeraduates.The juxtaposition of personal and population risk can
ead to further confusion. Although population-based prob-bilities may accurately represent the collective risk ofown syndrome for women of a particular age, an individ-al woman who presents during pregnancy is either carry-ng a fetus that has a chromosomal abnormality, or a fetushat does not. Although the probability of a Down syn-rome affected birth for a group of 37-year-old women isstimated at 1/122 (8/1,000), for any individual woman, its either 0 or it is 1. Although diagnostic tests like chorionicillus sampling and amniocentesis can provide a “yes” orno” answer, screening methods such as nuchal translu-
Probability Frequency
1:82 12.2/1,0001:122 8.2/1,0001:186 5.5/1,0001:242 4.1/1,000
) 1:190 5.3/1,0000.6–0.8% 6/1,000–8/1,000
0.5% 5/1,0001:300 3.3/1,000
L 2001.34
lifornia
ency and maternal serum screening provide a probability
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gure, despite the fact that the fetal condition is alreadyetermined. It is not surprising, then, that many womenonceive of their personal risk in a binary fashion—eitherheir fetus is affected, or it is not.13,19–21 At the same time,hose informing and counseling women about the use ofrenatal genetic testing typically describe risks in terms ofge- or screening-based rates or percentages. As Edwardsotes, “language is easily laid on top of mathematics toake it look as if individuals rather than collectives form
he foundation for our risk assessments.”13
HE PROCESS OF UNDERSTANDING RISK
he social and cultural context of reproductive decisionaking and its highly personal and value-laden natureake it entirely appropriate for women to interpret the riskgures that they are provided. As a result, women and theirartners may not always make choices that are reflective ofhe actual chance that a child will be affected by a particularondition.21 Kuppermann et al. noted that although coun-eling tends to focus on relatively short-term risks, includ-ng the risk of a procedure-related miscarriage or the risk ofiving birth to an affected infant, it is longer-term out-omes, such as a successful future pregnancy, that matterost to women.22
A given numerical risk may seem “high” or it may seemlow,” depending on the multitude of factors influencingisk perception to that individual. Shiloh and Saxe note thathe process of identifying a risk as high or low involvesransforming it into a question of acceptability.23 Is the riskcceptable or not? How burdensome is each of the possibleutcomes likely to be? How acceptable does each of themppear? Women who are considering testing should bencouraged to ask themselves these questions as a part ofheir decision-making process. Kuppermann et al. alsoound that pregnant women tend to consider the prospect ofDown syndrome–related birth as more burdensome than aiscarriage related to a diagnostic procedure.24
There are several ways in which a woman’s attitudes,revious experience, and baseline knowledge combine tonfluence the way that she understands the risk figures she
ust think about when making a decision about prenatalenetic testing.
nchoring
nvestigators have noted that risk perception prior toounseling is most strongly associated with postcounselingnterpretation of risk.20,23 Given the routine nature ofrenatal genetic testing, most women will have had anpportunity to think about the risk of genetic or congenitalisease in their offspring. As a result, they are likely toring some preconceived sense of their risk to the conver-ation in which testing options are discussed. This leads tophenomenon known as “anchoring,” which occurs whenperson has a previous conception of their risk, and that
onception “pulls” or “anchors’ the objective risk provided c
22
uring counseling in a direction that is either higher orower than “true” risk.20,23 Even after an “accurate” nu-
eric risk is provided, the woman’s preconception abouter risk will continue to affect her interpretation. Wertz etl. found, in their study of genetics counseling clinics, thator those clients who reported an interpretation of risk prioro counseling, the “pre-counseling interpretation of riskreceded all other variables, including numeric risk, in itstrength of association with post-counseling interpretationf risk.”20 Therefore, it would seem important for thoseounseling women about their testing options to addressheir clients’ preexisting notions about risk and to discusshem in the context of the risk information being provided.
raming
he way that a risk is framed can also influence how it isnterpreted.18,25 Simple changes in the format used toresent numerical risk information can influence perceptionnd subsequent choices. For example, presenting the risksf treatment for a disease in terms of the percent whourvive rather than the percent who die leads to a moreositive assessment of risk.17 Marteau found that presenta-ion as the chance of having an affected child resulted in aerception of higher risk and more uptake of testing thanid presentation of risk as the chance of having an unaf-ected, healthy child.26 In helping women understand theomplex risk information provided to them during theounseling process, it may be helpful to reframe riskgures. A woman who is “screen positive” on maternalerum screening and who is given a risk figure of 1/100 forDown syndrome–affected fetus can be reminded that the
hance that her fetus is not affected is 99/100 or 99%.
epresentativeness
epresentativeness is the degree to which a particularutcome is regarded as representative or typical of allotential outcomes of an intervention.20 For example, aouple who thinks of Chris Burke, a television actor withown syndrome, as typical of an individual with that
ondition will consider their risk lower than if they had aeighbor with a severely affected child who they thought ofs typical of someone with this condition.
vailability
vailability refers to the ease with which examples of theisked outcome can be brought to mind. The greater thevailability, the greater the likelihood of the outcome inuestion will seem.20 For example, risk will tend to benterpreted as higher if a woman has personal experienceith an affected child than if she does not. Wertz et al.
ound that having an affected child at home was associatedith a more pessimistic interpretation of risk.20 Genetic
ounselors typically have examples of individuals with
Volume 49, No. 3, May/June 2004
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ommon genetic conditions readily available, which mayartially account for the finding that they tend to interpretisks as more severe or more likely to occur than do theirlients.27 “Availability” may also partially explain thending that clients tend to interpret a given numerical risks lower than the counselor does. For example, risks in theange of 25% to 50% were regarded as high by mostounselors surveyed but were considered low to moderatey the majority of counseling clients.20 Both “availability”nd “representativeness” were likely at play in Leonard’snding that CF counseling clients who received a brochurebout testing, which included “modeling” a story about theutcomes in question, were more likely to consider the riskf having a child with CF high.28 They were also more
Table 2. Effective Use of Risk Information in Counseling
1. Assess baseline level of literacy and numeracy.2. Inquire about knowledge of the testing process and its outcomes.3. Identify preconceptions about personal risk of outcomes in question.4. Discuss personal experience or familiarity with conditions or tests in
question.5. Present numeric risk information.
a. Use rates to describe risk.b. Frame risk both in terms of the chance of an undesired outcome
and the chance of an unaffected infant or “successful” outcome.6. Assess application of risk information provided to the decision at
hand.a. Incorporate with personal values.b. Participate with partner or family in decision making.
Figure 1. Paling Perspective Scale © John Paling. Reprinte
ournal of Midwifery & Women’s Health • www.jmwh.org
ikely to perceive the disease as being severe. Wertz et al.oted that clients were more likely to appreciate risk aserious if that risk was discussed in terms of the client’sctual behavior.20
OW BEST TO COMMUNICATE RISKS
se of Baseline Risk in Counseling
he literature on risk perception provides the foundation forork that explores alternative methods for communicating
isk. Some of these findings will be valuable to those whorovide risk information about prenatal genetic testing.hese studies also confirm that women with lower educa-
ional attainment face particular challenges in understand-ng numeric risk information. Schwartz et al., in a study ofisk communication in the context of breast cancer screen-ng, found that subjects had improved comprehension ofheir risk if information about baseline risk was included inhe discussion.17 Baseline, or age-related, risk could easilye incorporated into prenatal genetic counseling (Table 2).aling has developed a method for visually representing theelative risk of various conditions, called the Paling Per-pective Scale. An adaptation of this scale that includesnformation about the risks of various birth outcomes coulde useful in assisting women to understand their risks29
Figure 1). A second scale developed specifically to visu-lly display the risk of Down syndrome is included inppendix A.
29
d with permission from Stallings and Paling, 2001.223
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se of Rate Versus Proportion
rimes and Snively conducted a study to determinehether women’s understanding of risk differed if that riskas expressed as a rate per 1,000 (e.g., 4 per 1,000) or asproportion with a numerator of 1 (e.g., 1 in 250).19 Theysed a convenience sample of women seeking care at therenatal clinics affiliated with the University of California,an Francisco. The study population of more than 600 wasiverse, including English, Spanish, and Chinese speakers.omen were asked to compare two risks for urinary tract
nfection and to indicate which risk was higher. Grimes andis coinvestigators chose urinary tract infection, rather thanown syndrome risk, to avoid the anxiety that might be
ssociated with a serious outcome. He found that womennderstood rates (e.g., 4/1,000) better than they understoodroportions (e.g., 1/250). Seventy-three percent accuratelydentified the higher risk when rates were used (2.6/1,000ersus 8.9/1,000), but only 56% could do so when propor-ions were used (1/384 versus 1/112). Approximately 20%f the women could not understand either format. Womennderstood rates better than proportions regardless of theirge, language, or educational attainment, although womenith higher levels of education had more correct responses
han those with high school education or less. Only half ofomen with 9 years of education or less evaluated rates
orrectly, and less than a third could correctly assessroportions. In his discussion, Grimes points out thatounselors and clinicians may be “causing unnecessaryonfusion” in their clients by the current practice of usingroportions in providing risk information. For example, thealifornia Expanded AFP Program provides risk estimates
n proportions in the results reports sent to providers.Van Vliet and Grimes replicated these findings in a group
f women from North Carolina.30 Again, rates were betternderstood than were proportions. Similarly, Schwartz etl. found better comprehension of risk when provided in arequency format rather than as a proportion or a percent.17
offrage and Gigerenzer, cognitive psychologists, point outhat, although mathematically probabilities, percentages,nd absolute frequencies can be equivalent, “natural fre-uencies improve the statistical thinking of experts andonexperts alike.”31
OW DOES RISK PERCEPTION INFLUENCE REPRODUCTIVENTENTION?
everal investigators have examined the degree to which aoman’s perception of her risk impacts her decisions abouthether to have a child. Shiloh and Saxe found that riskerception before counseling correlated strongly with re-roductive intention after counseling.23 This is consistentith the concept of “anchoring.” Although 3 of 4 subjects
hanged their risk perception after genetic counseling, onlyalf changed their reproductive intention. Wertz et al. notedhat a woman’s interpretation of her risk was a better
redictor of her reproductive intentions than was the w24
umerical risk she was given.20 She found that women,fter being presented with a numeric risk figure, assessedhat risk subjectively and used that subjective assessment touide decision making about reproduction.The health belief model can be helpful in understanding
he ways that perceptions about a medical problem, modi-ying variables such as attitudes and needs, and other cueso action work together to determine health-related behav-or.32 In the setting of prenatal diagnosis, perceptions wouldnclude a woman’s preexisting assumptions about her levelf risk for an affected child. Modifying factors mightnclude the desire to have a child, attitudes about disability,eelings about abortion, and the anticipated burden ofaising a child who has a disability. Cues can be internal,uch as previous experience with a specific disorder or withisability in general, or external, such as risk estimatesrovided by a counselor or facts about the genetic diseasen question.
The health belief model has been used to examineredictors of the use of genetic screening.28,33 Rowleyound that perception of susceptibility to (or risk of) diseasend perception of the seriousness of the disease wereelevant predictors.33 Leonard et al. noted that a woman’sotivation to undergo testing was related directly to the
erceived seriousness of the disease in question, her per-eived personal risk, and her knowledge.28 Once again, it isvident that it is a woman’s understanding of informationrovided during prenatal counseling and care, rather thanhe actual facts and figures provided, that determines thehoices she makes.
RENATAL GENETIC TESTING
he considerations raised by a review of the literature onisk perception and risk communication can inform ourttempts to educate and counsel women about their optionsor prenatal testing and screening. Several aspects ofrenatal testing make decision making in this context muchore complex than in the context of breast cancer screening
r risk of urinary tract infection. First, a woman consideringesting must simultaneously weigh several risk figures: 1)er risk of giving birth to an affected child, 2) her risk ofaving an abnormal test result, and 3) the risk that the testay cause a pregnancy loss. She must understand three riskgures simultaneously and then be able to compare them.iven what we know of women’s ability to comprehend
ven one risk figure, this task seems daunting. This risk-riskssessment is made even more complex because of thealue-laden nature of the potential outcomes beingeighed. Numerous hypothetical trade-offs are required in
he process of making a decision. How risks are perceivedndividually may differ from the way that they are per-eived in relationship to each other.
Second, most decisions about the use of prenatal testingre ultimately made by pregnant women, although often
ith the input of their partners. Findings on the relationshipVolume 49, No. 3, May/June 2004
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etween gender and risk perception have been inconsistent.hiloh and Saxe noted that risk perception by men revealedore congruence between objective and subjective risks
han did that of women. They did not find that objective riskontributed to risk perception by women in a significantay.23 Male risk perception correlated best with objective
isk as stated by a counselor, reproductive intentions,everity of the condition in question, and its treatability. Foromen, relevant factors were prior expectation of risk,hether communication during counseling had been neu-
ral, availability of prenatal diagnosis, and self-parenthoodoncept.23
Third, the process of making a decision about prenatalesting typically includes at least some discussion with theoman’s partner. This requires that both members of the
ouple have an adequate understanding of risk to discussheir options in a meaningful way and to understand eachther’s viewpoints. The negotiation about testing options isikely to involve not only two potentially different percep-ions of risk but also two somewhat different sets ofttitudes and prior experiences. The latter, as we have seen,ill influence how risk perception is translated into action.
ONCLUSIONS
any women seek prenatal genetic counseling to acquirehe information they need to make decisions about testing.ther women do not actively seek counseling, but theyust be informed about the testing options available to
hem in a way that enables them to make meaningfulhoices. For both groups of women, effective counselinghould include much more than just communication of riskgures. Because accurate comprehension of risk cannot bessumed, women and their partners need assistance innderstanding risk information and in thinking about howhis information can be used effectively in their reproduc-ive decision making. Several strategies are available toroviders that can help women and their partners optimizeheir understanding of risk and use risk information pro-uctively in their decision-making process.There is good evidence from both empiric researchers
nd cognitive psychologists that frequencies and rates areuch more easily understood and manipulated than are
ercentages or probabilities. Providers should take the timeo calculate and use frequencies in their discussions withounselees and try their best to use simple language iniscussing risk figures. This is particularly important forlients of low literacy and numeracy. Visual representationsf risk information also may be beneficial.It is evident that the way risk figures are framed impacts
he way they are interpreted. It may be helpful to include apecific discussion of the likelihood that the abnormalityeing tested for is not present, rather than relying com-letely on figures representing the risk of an undesirableutcome. Because preconceptions about risk are strongly
redictive of assessment of risk after counseling, a woman’s tournal of Midwifery & Women’s Health • www.jmwh.org
aseline understanding of her risk should be discussedlong with the new risk information being provided. Herersonal experience with or knowledge of individuals withhe condition being tested for will also influence how shessesses her risk. These experiences can be addressed in theounseling session as well.
The expansion in the use of screening tests for a varietyf genetic conditions means that primary obstetric provid-rs will be participating more and more in counselingatients. Whether it is counseling about the testing choicesvailable or counseling after receipt of screening results,ttention to the way that risk information is understood andsed will improve the quality of care received by pregnantomen and their partners. Providers should bear in mind
hat a woman’s individual values are much more importanto optimizing decision making than are her risks of anyarticular outcome.34 The aim should be to achieve aounseling process that enables women to comprehend riskell enough to allow it to inform their value-based decisionaking about the issues facing them during pregnancy.
EFERENCES
1. Marteau TM, Dormandy E. Facilitating informed choice inrenatal testing: How well are we doing? Am J Med Genet 2001;06:185–90.
2. ACOG Practice Bulletin. Clinical management guidelines forbstetrician-gynecologists. Prenatal diagnosis of fetal chromosomalbnormalities. Obstet Gynecol 2001;97(5 Pt 1; suppl):1–12.
3. American College of Obstetricians and Gynecologists. Pre-onception and prenatal carrier screening for cystic fibrosis: Clinicalnd laboratory guidelines. Washington (DC): American College ofbstetricians and Gynecologists, 2001.
4. American College of Obstetricians and Gynecologists. Ante-atal diagnosis of genetic disorders. Washington (DC): Americanollege of Obstetricians and Gynecologists, 2002.
5. Cuckle HA. Estimating a woman’s risk of having a pregnancyssociated with Down’s syndrome using her age and serum alpha-etoprotein level. Br J Obstet Gynaecol 1987;94:387.
6. Hook EB, Albright SG. Mutation rates for unbalanced Rob-rtsonian translocations associated with Down syndrome. Evidenceor a temporal change in New York State live births 1968–1977.m J Hum Genet 1981;33:443–54.
7. Hook EB, Cross PK, Schreinemachers DM. Chromosomalbnormality rates at amniocentesis and in live-born infants. JAMA983;249:2034–8.
8. Souter VL, Nyberg DA. Sonographic screening for fetalneuploidy: First trimester. J Ultrasound Med 2001;20:775–90.
9. Schneider KA. The 1998 professional status survey. Perspectenet Counsel 1998;20:S1–S8.
10. Browner CH, Preloran M, Press NA. The effects of ethnicity,ducation and an informational video on pregnant women’s knowl-dge and decisions about a prenatal diagnostic screening test. Patientduc Couns 1996;27:135–46.
11. Marteau TM. Towards informed decisions about prenatal
esting: A review. Prenat Diagn 1995;15:1215–26.225
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12. O’Cathain A, Thomas K, Walters SJ, Nicholl J, Kirkham M.omen’s perceptions of informed choice in maternity care. Mid-ifery 2002;18:136–44.
13. Edwards A, Prior L. Communication about risk—Dilemmasor general practitioners. The Department of General Practice Work-ng Group, University of Wales College of Medicine. Br J Gen Pract997;47:739–42.
14. Kessler S, Levine EK. Psychological aspects of genetic coun-eling. IV. The subjective assessment of probability. Am J Med Genet987;28:361–70.
15. Michie S, Marteau TM. Genetic counseling: Some issues ofheory and practice. In Marteau TM, Richards M. The troubled helix:ocial and psychological implications of the new human genetics.ambridge: Cambridge University Press, 1996.
16. Walker AP. Genetic counseling. In Rimoin DL, Conner JM,yeritz. Emery and Rimoin’s principles and practice of medicalenetics, 3rd ed. New York: Churchill Livingstone, 1997:595–618.
17. Schwartz LM, Woloshin S, Black WC, Welch HG. The role ofumeracy in understanding the benefit of screening mammography.nn Intern Med 1997;127:966–72.
18. Chase GA, Faden RR, Holtzman NA, Chwalow AJ, LeonardO, Lopes C, et al. Assessment of risk by pregnant women: Implications
or genetic counseling and education. Soc Biol 1986;33:57–64.
19. Grimes DA, Snively GR. Patients’ understanding of medicalisks: Implications for genetic counseling. Obstet Gynecol 1999;93:10–4.
20. Wertz DC, Sorenson JR, Heeren TC. Clients’ interpretation ofisks provided in genetic counseling. Am J Hum Genet 1986;39:253–64.
21. Lippman-Hand A, Fraser FC. Genetic counseling: Parents’ re-ponses to uncertainty. Birth Defects Orig Artic Ser 1979;15:325–39.
22. Kuppermann M, Feeny D, Gates E, Posner SF, Blumberg B,
ashington AE. Preferences of women facing a prenatal diagnostic t26
hoice: Long-term outcomes matter most. Prenat Diagn 1999;19:11–6.
23. Shiloh S, Saxe L. Perceptions of recurrence risks by geneticounselees. Psychol Health 1989:45–61.
24. Kuppermann M, Nease RF, Learman LA, Gates E, Blumberg, Washington AE. Procedure-related miscarriages and Down syn-rome-affected births: Implications for prenatal testing based onomen’s preferences. Obstet Gynecol 2000;96:511–6.
25. Tversky A, Kahneman D. The framing of decisions and thesychology of choice. Science 1981;211:453–8.
26. Marteau TM. Framing of information: Its influence uponecisions of doctors and patients. Br J Soc Psychol 1989;28:89–94.
27. Kessler S. Process issues in genetic counseling. Birth Defectsrig Artic Ser 1992;28:1–10.
28. Leonard KP, Bartholomew LK, Swank PR, Parcel GS. Aomparison of two approaches to education about carrier testing forystic fibrosis. J Genet Counsel 1995:97–113.
29. Stallings SP, Paling JE. New tool for presenting risk in ob-tetrics and gynecology. Obstet Gynecol 2001;98:345–9.
30. van Vliet HA, Grimes DA, Popkin B, Smith U. Lay persons’nderstanding of the risk of Down’s syndrome in genetic counseling.r J Obstet Gynaecol 2001;108:649–50.
31. Hoffrage U, Lindsey S, Hertwig R, Gigerenzer G. Medicine:ommunicating statistical information. Science 2000;290:2261–2.
32. Rosenstock IM. Historical origins of the health belief model.n: Becker M. The health belief model and personal health behavior.horofare (NJ): Charles Slack, 1974:1–8.
33. Rowley PT. Prenatal screening for hemoglobinopathies. Am Jum Genet 1991;49:466–7.
34. Harris RA, Washington AE, Feeny D, Kuppermann M. Deci-ion analysis of prenatal testing for chromosomal disorders: What do
he preferences of pregnant women tell us? Genet Test 2001;5:23–32.Volume 49, No. 3, May/June 2004
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Appendix A. Reprinted with permission from John Paling, PhD, Risk Communication Institute. Figure courtesy of Nicole Dudley, Graphic Designer.
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