Flags

Women's Health and Education Center (WHEC)

Obstetrics

Print this ArticleShare this Article

Genetic Counseling and Genetic Screening

WHEC Practice Bulletin and Clinical Management Guidelines for healthcare providers. Educational grant provided by Women's Health and Education Center (WHEC).

Genetic testing is poised to play a greater and greater role in the practice of obstetrics and gynecology. Approximately 3% of liveborn infants have a major congenital anomaly. About one half of these anomalies are detected at birth; the remainder becomes evident later in childhood or, less often, adulthood. Although non-genetic factors may cause malformations, genetic factors are usually responsible. In addition, more than 50% of first-trimester spontaneous abortions and at least 5% of stillborn infants have chromosomal abnormalities. Human genetics and molecular testing is playing an increasingly important role in obstetric and gynecologic practice. It is essential that obstetricians and gynecologists are aware of the advances in the understanding of genetic disease and the fundamental principles of molecular testing and genetic screening. As genetics is integrated into routine genetic basis for reproductive disorders, common diseases, and cancer with improved high throughput technology for genetic testing will expand testing opportunities and influence treatment options and prevention strategies. To assure patients of the highest quality of care, physicians should be familiar with the currently available array of genetic tests, as well as with their limitations.

The purpose of this document is to discuss the principles of genetic counseling and genetic screening. Disorders amenable to genetic screening and prenatal diagnosis are also enumerated. Salient principles of the genetic counseling process are described. A variety of molecular diagnostic tests are available to determine whether an individual or fetus has inherited a disease-causing gene mutation. It can identify other family members or relatives at risk for the disorder or at risk for being a carrier. The gift of life can be "perfect" even in the presence of serious problems (1).

Genetic History:

To address this question, some obstetricians find it helpful to elicit genetic information through the use of questionnaires or checklists that are often constructed in a manner that requires action only to positive responses. A form that has been modified from that recommended by the American College of Obstetricians and Gynecologists (ACOG) is stated below (2):

Prenatal Genetic Screen

Name: _______________________ Patient # ______________ Date: _________

1. Will you be 35 years or older when the baby is due?

Yes____ No___

2. Have you, the baby's father, or anyone in either of your families ever had any of the following disorders?

Down syndrome (mongolism)

Other chromosomal abnormalities

Neural tube defect, i.e., spina bifida, anencephaly

Hemophilia

Muscular dystrophy

Cystic fibrosis

If yes, indicate the relationship of the affected person to you or the baby's father:





Yes____ No____

Yes____ No____

Yes____ No____

Yes____ No____

Yes____ No____

Yes____ No____


3. Do you or the baby's father have a birth defect? If yes, who has the defect and what is it?



Yes____ No____


4. In any previous marriages, have you or the baby's father has a child born, dead or alive, with birth defect not listed in question 2 above?



Yes____ No____


5. Do you or the baby's father have any close relatives with mental retardation?

If yes, indicate the relationship of the affected person to you or the baby's father:

Indicate the cause, if known:



Yes___ No___

6. Do you, the baby's father, or a close relative in either of your families have a birth defect, any familial disorder, or a chromosomal abnormality not listed above?

If yes, indicated the condition and the relationship of the affected person to you or to the baby's father:




Yes____ No____


7. In any previous marriage, have you or the baby's father had a stillborn child or three or more first-trimester spontaneous pregnancy losses?

Have either of you had a chromosomal study?


Yes____ No____

Yes____ No____

8. If you or the baby's father is of Jewish ancestry, have either of your been screened for Tay-Sachs disease, Canavan disease, or cystic fibrosis?

If yes, indicate who and the results:




Yes____ No_____


9. If you or the baby's father is black, have either of you been screened for sickle cell trait?

If yes, indicate who and the results:




Yes___ No___


10. If you or the baby's father is Italian, Greek, or Mediterranean background, have either of you been tested for beta-thalassemia?

If yes, indicate who and the results:




Yes___ No___


11. If you or the baby's father is of Philippine or Southeast Asian ancestry, have either of you been tested for alpha-thalassemia?

If yes, indicate who and the results:




Yes___ No___


12. Irrespective of ethnic group, have you or the baby's father been screened for cystic fibrosis?

Yes___ No___


13. Excluding iron and vitamins, have you taken any medications or recreational drugs since becoming pregnant or since your last menstrual period? (include non-prescription drugs). If yes, give name of medication and time taken during pregnancy:




Yes___ No___


14. Have you currently been taking folic acid supplements?

Yes___ No___


One should inquire into the health status of first-degree relatives (siblings, parents, offspring), second-degree relatives (nephews, nieces, aunts, uncles, grandparents), and third-degree relatives (first cousins, especially maternal). Adverse reproductive outcomes such as repetitive spontaneous abortions, stillbirths, and anomalous liveborn infants should be pursued. The prevalence of chromosomal abnormalities in clinically recognized early pregnancy loss is greater than 50%. Fetuses with aneuploidy account for 6-11% of all stillbirths and neonatal deaths (3). Couples having such histories should undergo chromosomal studies in order to exclude balanced translocations. If a birth defect exists in a second-degree relative (uncle, aunt, grandparent, nephew, niece) or third-degree relative (first cousin), the risk for that anomaly will usually not prove substantially increased over that in the general population. For example, identification of a second- or third-degree relative with an autosomal recessive trait places the couple at little increased risk for an affected offspring, an exception being if the patient and her husband are consanguineous. However, a maternal first cousin with an X-linked recessive disorder could identify a couple at increased risk for a similar occurrence.

Parental ages should also be recorded. Advanced maternal age warrants discussion irrespective of a physician's personal convictions regarding pregnancy termination, as knowledge of an abnormality may affect obstetric management. Ethnic origin should be recorded because certain genetic diseases are increased in selected ethnic groups. Such queries apply for both gamete donors as well as couples achieving pregnancy by natural means (4). Chromosomal abnormalities that are compatible with life but cause considerable morbidity occur in 0.65% of newborns, and structural chromosomal rearrangements that will eventually affect reproduction occur in 0.2% of newborns. Consequently, screening and diagnostic programs to detect the most common autosomal trisomies in liveborn infants, including Down syndrome, are well established.

Genetic Counseling:

Pivotal to counseling is communicating in terms that are readily comprehensible to patients. It is useful to preface remarks with a few sentences recounting the major causes of genetic abnormalities, such as cytogenetic, single-gene, polygenic / multifactorial ("complex"), and environmental (teratogen) causes. Although genetic counseling may require referral to a clinical geneticist, it is impractical for obstetricians to refer all patients with genetic inquires (5). Indeed, obstetricians performing diagnostic procedures such as amniocentesis must counsel their patients before such a procedure. Therefore, salient principles of the genetic counseling process are described.

Communication: Repetition is essential. Allow the couple not only to ask questions but to talk with one another to formulate their concerns. Written information (letters or brochures) can serve as a couple's permanent record, allaying misunderstanding and assisting in dealing with relatives. Pre-printed forms and information describing common problems (e.g., advanced maternal age) have the additional advantage of emphasizing that the couple's problem is not unique. Irrespective of how obvious a diagnosis may seem, confirmation is always obligatory (6). Proper counseling requires proper diagnosis.

Nondirective Counseling: In genetic counseling, one should provide accurate genetic information yet ideally dictate no particular course of action. Of course, completely nondirective counseling is probably unrealistic. For example, a counselor's unwitting facial expressions may expose his or her unstated opinions. Merely offering antenatal diagnostic services implies approval. Despite the difficulties of remaining truly objective, one should attempt to provide information and then support the couple's decision. Genetic screening for any clinical purpose should be tied to the availability of intervention, including prenatal diagnosis, counseling, reproductive decision making, lifestyle changes, and enhanced phenotype screening (7). Nondirective counseling before prenatal diagnostic testing does not require a patient to commit to pregnancy termination if the result is abnormal.

Psychological Defenses: If not appreciated, psychological defenses can impede the entire counseling process. Couples experiencing abnormal pregnancy outcomes manifest the same grief reactions that occur after the death of a loved one: denial, anger, guilt, bargaining, and resolution. An additional psychological consideration is that of parental guilt. Appreciating the psychological defenses helps one to understand the failure of ostensibly intelligent and well-counseled couples to comprehend genetic information (8). An additional psychological consideration is that of parental guilt. One naturally searches for exogenous factors that might have caused an abnormal outcome. In the process of such a search, guilt may arise. Conversely, a tendency to blame the spouse may be seen. Usually, guilt or blame is not justified, but occasionally the "blame" is realistic (e.g., in autosomal dominant traits). Fortunately, most couples can be assured that nothing could have prevented a given abnormality in their offspring.

Advanced Paternal Age -- risks to the fetus:

Although advancing paternal age does not affect pregnancy outcome, effects on genetic disease are less completely understood. Advanced maternal age confers increased risk for aneuploidy. This probably does not hold for advanced paternal age. A few studies indicate an increased frequency of aneuploidy in sperm in the sixth and seventh decades. However, risks are only marginally increased above background, and there remains no indication that a liveborn pregnancy risk is increased. By contrast, a paternal age effect exists for single gene mutation, most relevantly de novo autosomal dominant mutations. A pregnancy sired by a man in his sixth decade or beyond carries perhaps a 1% increase, owing to the cumulative effects of single gene mutations at many loci. Unfortunately, prenatal testing is not applicable because hundreds of different loci could be involved. There is no evidence of a maternal age effect for single gene disorders. There is general agreement that advancing paternal age predisposes the fetus to mutations in autosomal diseases such as neurofibromatosis, achondroplasia, Apert syndrome, and Marfan syndrome. The increased risk rises exponentially, rather than linearly, with increasing paternal age.

Advanced maternal age increases risk of having a liveborn infant with autosomal trisomies 21, 18, or 13, or with the sex chromosome aneuploidies 47,XXY or 47,XXX. Genetic counseling traditionally has been offered when a woman will be 35 years of age or older at her estimated delivery date. Currently, it is not possible to screen prenatally for all autosomal dominant and X-linked diseases in the presence of advanced paternal age. Only genetic counseling on an individual basis is recommended for couples to address their specific concerns if advancing paternal age is an issue. The risk of fetal aneuploidy can be determined by referring to maternal age-specific aneuploidy risk tables or using age-adjusted risks after screening. These cutoffs are based on the specific detection rate and screen-positive rate of the screening approach that is used. After the diagnosis of a chromosomal abnormality, the patient should receive detailed information, if known, about the natural history of individuals with the specific chromosomal finding. In many cases, it may be very helpful to refer the patient to a genetic counselor or clinical geneticist and national groups such as The National Down Syndrome Society or National Down Syndrome Congress to help the patient make an informed decision (9). Referral to parent support groups, counselors, social workers, or clergy may provide additional information and support. In the past decade, numerous markers and strategies for Down syndrome screening have been developed. Algorithms that combine ultrasound and serum markers in the first and second trimester have been evaluated. Furthermore, the practice of using age cutoff to determine whether women should be offered screening or invasive diagnostic testing has been challenged.

Genetic and Molecular Diagnostic Screening:

It implies routine monitoring for the presence or absence of a given condition in apparently normal individuals. Screening is now offered routinely for all individuals of certain ethnic groups to identify those individuals heterozygous for a given autosomal recessive disorder. Knowledge of human genetics has increased dramatically in the past few decades. The genetic basis of disease and the response to therapy is rapidly being elucidated and may soon become a part of routine medical practice. A draft of the human genome was published in 2001 (10). This project produced a detailed map of the genes, markers, and other landmarks along each chromosome. It is hoped that these maps will facilitate the development of genetic screening and diagnostic tests, as well as novel therapies, technologies, and strategies for prevention. Ideally, all women should be offered aneuploidy screening before 20 weeks of gestation, regardless of maternal age. It is not practical to have patients choose from among the large array of screening strategies that might be used. A strategy that incorporates both first- and second-trimester screening should be offered to women who seek prenatal care in the first trimester. The choice of screening test depends on many factors, including gestational age at first prenatal visit, number of fetuses, previous obstetric history, family history, availability of nuchal translucency measurement, test sensitivity and limitations, risk of invasive procedures, desire for early test results, and options for earlier termination.

Genetic Screening in Various Ethnic Groups (11):

Ethnic Group

Disorder

Screening Test

All ethnic groups

Cystic fibrosis (CF)

DNA analysis of selected panel of 23 CFTR mutations (alleles present in 0.1% of the general U.S. population).

Ashkenazi Jewish

Tay-Sachs disease



Canavan disease


Familial dysautonomia

Decreased serum hexosaminidase --A or DNA analysis for selected alleles.


DNA analysis for selected alleles.


DNA analysis for selected alleles.

Black

Sickle cell anemia

MCV <80%, followed by hemoglobin electrophoresis.

Cajuns

Tay-Sachs disease

DNA analysis for selected alleles.

French-Canadians

Tay-Sachs disease

DNA analysis for selected alleles.

Mediterranean people (Italians, Greek)

beta-Thalassemia

MCV <80%, followed by hemoglobin electrophoresis if iron deficiency excluded.

Southeast Asians (Filipinos, Chinese, African, Vietnamese, Laotian, Cambodian)

alpha-Thalassemia

MCV<80%, followed by hemoglobin electrophoresis if iron deficiency excluded.

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR); Mean Corpuscular Volume (MCV)

Molecular Diagnostic Testing:

Advances in our understanding of the molecular basis of inherited disorders have led to the development of DNA-based tests, which may be used for the confirmation of a diagnosis, prenatal diagnosis and carrier testing. Molecular diagnostic testing is now widely available for a number of single gene disorders, such as Tay-Sachs disease, Canavan disease, sickle cell disease, cystic fibrosis (CF), muscular dystrophies, and fragile X syndrome. Molecular-cytogenetic testing has been developed for the detection of chromosomal abnormalities, including aneuploidy and submicroscopic deletions and duplications (11). DNA can be obtained from many sources, including blood lymphocytes, skin, hair, cheek cells, and paraffin tissue blocks. Most diagnostic laboratories prefer either blood samples or buccal swabs for DNA testing. Cultured amniocytes, chorionic villi, and fetal blood are used for prenatal DNA testing of the fetus.

Accuracy and limitations of molecular testing: Direct detection of a point mutation, deletion, or duplication is the most accurate test. However, the accuracy of molecular diagnosis also is dependent on an accurate diagnosis. If an affected relative is not available to identify the presence of a mutation or if medical records are not available to confirm the diagnosis, this may decrease the accuracy of testing for a specific mutation and for the suspected genetic disorder. One of the limitations of molecular diagnostic testing is test sensitivity. There are a number of factors that determine the ability to detect mutations. Many genetic disorders result from a variety of genetic alterations. For example, more than 800 mutations have been reported in patients with CF. The mutation detection rates for many genetic disorders, including neurofibromatosis, CF, and hemophilia, is less than 100%. Therefore, the absence of a mutation does not exclude the possibility that an individual may be a carrier (12). Furthermore, there may be ethnic differences in the detection rates; 97% of CF mutations have been identified in the Ashkenazi Jewish population while only 30% in Asian Americans. The incidence and carrier risk for some genetic disorders also is dependent on ethnicity and has led to the current recommendations for carrier screening for specific genetic disorders. Differences in tests sensitivity and the prevalence of mutations must be considered for each individual genetic disorder and discussed with the patient prior to testing. Disease prevalence and test sensitivity should be taken into account in future recommendations for molecular-based carrier testing.

Another limitation to molecular testing is genetic heterogeneicity. In some cases, there may be more than one gene or chromosomal locus responsible for a genetic disorder. For example, at least two genes have been identified that cause tuberous sclerosis, an autosomal dominant disorder. Conversely, mutations in a single gene can cause different phenotypes. For example, mutation in fibroblast growth factor receptor 3 (FGFR3) are associated with several types of skeletal disorders, including achondroplasia, hypochondroplasia, thanatophoric dysplasia, and with craniosynostosis (e.g., Crouzon's disease, coronal synostosis). In some diseases, the identification of a genetic mutation cannot precisely predict the phenotype because of reduced penetrance or phenotypic variability or both. For example, 85% of women with a BRCA1 mutation develop breast cancer during their lifetime; therefore, the finding of a BRCA1 mutation indicates a strong predisposition to breast cancer but it does not indicate which women with the mutation will develop a malignancy. Some genetic disorders are highly variable even within families with the same mutation. Therefore, it may only be possible to provide patients with a description of the natural history of the disorder and an estimate of the frequency of specific features in patients with similar mutations.

Screening Neonates:

The frequency of major birth defects is 2 to 3%, based on the definition of a defect causing death, a severe dysfunction, or a structural malformation requiring surgery. In the United States, neonates have long been mandated in all states to be screened for phenylketonuria and hypothyroidism, which are amenable either to dietary or hormonal treatment, respectively. The number of disorders for which neonates are screened varies state by state. One could theoretically screen neonates for many other genetic disorders. Screening is actually recommended for relatively few disorders because prerequisites essential for initiating screening programs are not usually met. Widespread testing is ordinarily performed only if an abnormal finding would alter clinical management. In the United States, most commonly mandated are selected inborn errors of metabolism that include galactosemia (diet treatment), sickle cell anemia (early administration of antibiotics), and 21-hydroxylase adrenal hyperplasia (cortisol administration). Other disorders are mandated less commonly, usually using mass spectrometry. The March of Dimes recommends screening for 30 disorders as well as for deafness. Disorders explicitly enumerated by the ACOG and the U.S. Health Resources and Services Administration (HRSA) include not only phenylketonuria, hypothyroidism, galactosemia, sickle cell anemia, and adrenal hyperplasia, but also biotinidase deficiency, congenital toxoplasmosis, CF (postnatal), homocystinuria, maple syrup urine disease, and medium chain acyl-CoA dehydrogenase deficiency.

The ACOG and HRSA note that although possible, to screen for disorders of fatty acid oxidation, organic acids and urea cycle, there is less experience. Considerable recent attention is being given to screening for deafness. More than 70 genes are being given to screening for deafness (13). As accepted principle is that screening is not attempted for neonates with untreatable disorders. Thus, neonatal screening is not recommended for chromosomal abnormalities, Tay-Sachs disease, and Duchenne muscular dystrophy. Major etiologic categories include chromosomal abnormalities (1 in 160 live births), single-gene or Mendelian disorders, polygenic / multifactorial disorders, and disorders caused by exogenous factors (teratogens).

Screening Adults:

The ACOG recommends population screening for selected disorders, seeking asymptomatic heterozygotes in families in which no affected individual has been born. These autosomal recessive disorders are amenable to prenatal diagnosis and are listed above. Since 2001, screening for cystic fibrosis (CF) has been recommended by the ACOG and the American College of Medical Genetics (ACMG), with guidelines modified by ACOG in late 2005 (14). A key decision is whether to screen both the mother and father together (concurrent) or to screen only the mother (sequential) for CF; if only the mother is screened, the father would be studied only if the mother were a carrier. Either approach is acceptable. Screening both partners obviously produces the highest detection rate, although not by much. The downside is that one partner will be a carrier significantly more often (two fold), thus generating more anxiety and requiring follow-up more often. In couples of black, Hispanic, and Asian origin, it was originally stated that CF screening should be "made available". There were no specific recommendations for distinguishing between "offer" and "made available". If applying this, perhaps a brief informative statement about CF could be followed by informing the patient that CF screening exists. More recently, it has become obvious that it was often unwieldy to assign a single ethnicity to a given patient. Moreover, ACOG has estimated that two thirds of obstetricians were offering CF screening to all pregnant patients. Thus, it is now considered reasonable to offer CF screening to all pregnant women.

Genetic screening to detect heterozygotes in the non-pregnant and, if not already evaluated, in the pregnant population is appropriate for the following autosomal recessive disorders: Tay-Sachs disease, Canavan disease, familial dysautonomia in Jewish populations; Tay-Sachs disease in Cajun and French-Canadian populations; CF in all populations; alpha-thalassemia in Asians; beta-thalassemia in Mediterranean populations (Greek and Italians); and sickle cell disease in blacks.

Ethical Issues in Genetic Testing:

Although ethical questions related to genetic testing have been recognized for some time, they have gained a greater urgency because of the rapid advances in the field as a result of the success of the Human Genome Project. The pace at which new information about genetic diseases is being developed and disseminated is astounding. Thus, the ethical obligations of clinicians start with the need to maintain competence in the face of this evolving science. One of the pillars of professionalism is social justice, which would oblige physicians to "promote justice in the health care system, including the fair distribution of health care resources". Patients should be informed that genetic testing could reveal that they have, are at risk for, or are a carrier of a specific disease. The results of testing might have important consequences or require difficult choices regarding their current or future health, insurance coverage, career, marriage, or reproductive options. There are at least two issues that relate to the intersection of genetics and assisted reproductive technology (ART). In the first instance, there is need to consider whether all individuals, regardless of genotype, should have access to ART using their own gametes. Second is the question of the extent to which pre-implantation genetics should be used in pursuit of the "genetically ideal" child.

The ACOG Committee on Ethics and Genetics recommend the following guidelines:

  1. Clinicians should be able to identify patients within their practices who are candidates for genetic testing and should maintain competence in the fact of increasing genetic knowledge.
  2. Obstetrician -- gynecologists should recognize that geneticists and genetic counselors are an important part of health care team and should consult with them and refer as needed.
  3. Discussions with patients about the importance of genetic information for their kindred, as well as a recommendation that information be shared with potentially affected family members as appropriate, should be a standard part of genetic counseling.
  4. Obstetrician -- gynecologists should be aware that genetic information has the potential to lead to discrimination in the workplace and to affect an individual's insurability adversely. In addition to including this information in counseling materials, physicians should recognize that their obligation to professionalism includes a mandate to prevent discrimination. Steps that physician can take to fulfill this obligation could include, among others, advocacy for legislation to ban genetic discrimination.

With the increase in the number of clinical genetic tests requested by health care providers, there has been an increase in direct-to-consumer advertising and offering of genetic tests, including at-home tests and those provided by private companies. Marketing of genetic testing, although similar to direct-to-consumer advertising of prescription drugs, raises additional concerns and considerations. These include issues of limited knowledge among patients and health care providers of available genetic tests, difficulty in interpretation of genetic testing results, lack of federal oversight of companies offering genetic testing, and issues of privacy and confidentiality. Until all of these considerations are addressed, direct or home genetic testing should be discouraged because of the potential harm of a misinterpreted or inaccurate result (15). The U.S. Food and Drug Administration has not reviewed any of the at-home genetic tests, because of this, the validity and accuracy of many of these tests are unknown. All genetic testing should be provided only after consultation with a qualified health care professional.

Summary:

Principles of genetic counseling include adequate communication, appreciation of psychological defenses, and adherence to nondirective counseling. Genetics is taking an increasingly prominent role in the practice of obstetrics and gynecology. Gene identification, characterization of disease-causing mutations, and advances in genetic technology have led to an increased number of available genetic tests, which may be used for the diagnosis of genetic disorders, carrier detection, and prenatal or pre-implantation genetic diagnosis. Testing for a specific genetic disorder most often occurs in an obstetric setting based on either family history or the couple's ethnicity. Genetic counseling should be offered to couples at risk so they can review the nature of the disorder, the inheritance pattern, their specific risk for being a carrier and for having a child with the disorder, the current availability of prenatal and postnatal testing as well the accuracy and limitation of testing, and their reproductive options. Preconceptional genetic screening and counseling can identify couples at risk for having offsprings with a genetic disorder and provide them with information that enables them to make informed decisions regarding their reproductive options.

Given such a pivotal role for genetic factors, medical genetics becomes integral to the practice of modern obstetrics. In general, testing is offered to individuals or couples identified as being at risk for a genetic disorder based on their family history, medical history, or ethnicity. Determination of an individual's carrier status for a genetic disorder provides a more accurate estimate of their risk of having an affected offspring and allows an individual or couple to consider prenatal testing options. Obstetricians and gynecologists must attempt to determine whether a couple, or anyone in their family, has a heritable disorder or is at increased for abnormal offspring.

Acknowledgment: Women's Health and Education Center (WHEC) expresses gratitude to Dr. John P. O'Grady, Professor, Obstetrics and Gynecology, Tufts University School of Medicine, Medical Director Mercy Perinatal Service, for his priceless contribution in preparing the series on Genetics and The Prenatal Testing.

Suggested Reading:

  1. World Health Organization (WHO)
    Genetic Counselling Services
    Control of Genetic Diseases

  2. National Institutes of Health (NIH)
    Educating health-care professionals about genetics and genomics

  3. Gene Tests
    Funded by the National Institutes of Health

References:

  1. Boehm FH. Having a perfect child. Obstet Gynecol 2007;109:444-445
  2. Simpson JL, Holzgreve W. Genetic counseling and prenatal testing. In Obstetrics: Normal and Problem Pregnancies; 5th edition. Eds: Gabbe SG, Niebyl JR, Simpson JL. Publisher: Churchill Livingstone Elsevier; 2007
  3. Gardner RJ, Sutherland GR. Chromosome abnormalities and genetic counseling. 3rd ed. New York (NY): Oxford University Press; 2004. (Level III)
  4. Morgan MA, Driscoll DA, Zinberg S et al. Impact of self-reported familiarity with guidelines for cystic fibrosis carrier screening. Obstet Gynecol 2005;105:1355-1341
  5. Simpson JL, Elias S. Genetics in Obstetrics and Gynecology; ed 3, Philadelphia, WB Saunders, 2003
  6. Genetics and Public Policy Center. Genetic testing practice guidelines: translating genetic discoveries into clinical care. Washington, DC: GPPC; 2006. Retrieved July 24, 2008. Available at: http://www.dnapolicy.org/images/issuebriefpdfs/Professional_Guidelines_Issue_Brief.pdf
  7. Medical professionalism in the new millennium: a physician charter. ABIM Foundation: American Board of Internal Medicine; ACP-ASIM Foundation. American College of Physicians -- American Society of Internal Medicine; European Federation of Internal Medicine. Ann Intern Med 2002;136:243-246
  8. ACOG Committee Opinion. Genetics in Obstetrics and Gynecology. Washington, DC, American College of Obstetricians and Gynecologists, 2002
  9. ACOG Practice Bulletin. Invasive prenatal testing for aneuploidy. Number 88, December 2007
  10. The human genome. Science 2001;291:1145-1434
  11. ACOG Technology Assessment in Obstetrics and Gynecology No. 1. Genetics and molecular diagnostic testing. Obstet Gynecol 2002;100:193-211
  12. Roche PA, Annas GJ. DNA testing, banking, and genetic privacy. N Engl J Med 2006;355:545-546
  13. Prasad S, Cucci RA, Green GE et al. Genetic testing for hereditary hearing loss: connexin 26 (GJG2) allele variants and two novel deafness-causing mutations (R32C and 645-648delTAGA). Hum Mutat 2000;16:502-510
  14. ACOG Committee Opinion. Update on carrier screening for cystic fibrosis. Washington, DC, The American College of Obstetricians and Gynecologists, Report 325; 2005.
  15. ACOG Committee Opinion. Direct-to-consumer marketing of genetic testing. Washington, DC, The American College of Obstetricians and Gynecologists. Number 409; June 2008

Published: 6 August 2009

Women's Health & Education Center
Dedicated to Women's and Children's Well-being and Health Care Worldwide
www.womenshealthsection.com