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Antenatal Diagnosis

National Institutes of Health
Consensus Development Conference Statement
March 5-7, 1979

Conference artwork, the torso of preganant woman who is cradling her abdomen.

This statement is more than five years old and is provided solely for historical purposes. Due to the cumulative nature of medical research, new knowledge has inevitably accumulated in this subject area in the time since the statement was initially prepared. Thus some of the material is likely to be out of date, and at worst simply wrong. For reliable, current information on this and other health topics, we recommend consulting the National Institutes of Health's MedlinePlus http://www.nlm.nih.gov/medlineplus/.

This statement was originally published as: Antenatal Diagnosis. NIH Consens Statement 1979 Mar 5-7;2(2):11-15.

For making bibliographic reference to the statement in the electronic form displayed here, it is recommended that the following format be used: Antenatal Diagnosis. NIH Consens Statement Online 1979 Mar 5-7 [cited year month day];2(2):11-15.

Introduction

A Consensus Development Conference on Antenatal Diagnosis was held at the National Institutes of Health on March 5-7, 1979. The purpose of the conference was to assess the state of the art of techniques used in prenatal diagnosis; the legal, ethical, and social and economic implications of their use; appropriate applications of these techniques at present; and needs for additional research on their use.

The NIH consensus development program brings together practicing physicians, biomedical research scientists, consumers, and others in an effort to reach general agreement on the safety and efficacy of a medical technology, whether it be a drug, device or procedure.

At the antenatal diagnosis meeting, three broad categories of obstetrical techniques were discussed:

  • Predictors of hereditary disease and congenital defects. These include mid-trimester amniocentesis, fetoscopy, alpha-fetoprotein measurements, and ultrasound;
  • Predictors of fetal maturity, including third-trimester amniocentesis and ultrasound; and
  • Predictors of fetal distress, including monitoring during labor.

 

Before the meeting, task forces prepared preliminary reports on each of the three topics, summarizing the issues and giving recommendations. These draft reports were disseminated widely to obstetrical researchers, practicing obstetricians and gynecologists, lawyers, bioethicists, consumers, and voluntary associations concerned with pregnancy and childbirth. The reports prompted many people to submit written statements before the conference and provoked much debate during the meeting. As a result of this discussion, task force members reviewed and in some cases revised the recommendations made in draft reports. Final reports were published in August of 1979.  

Predictors of Hereditary Disease or Congenital Defects

The 12-member Task Force on Predictors of Hereditary Disease or Congenital Defects, chaired by Dr. Michael M. Kaback (Professor of Pediatrics and Medical Genetics, U.C.L.A. School of Medicine) weighed the risks and benefits of amniocentesis and other procedures that enable physicians to recognize defective fetuses as early as the fourth month of pregnancy.

They recommended that health professionals responsible for the care of pregnant women should be aware of techniques now available for early diagnosis of fetal defects, and should be prepared to identify and advise couples who are likely candidates for prenatal diagnostic services.

Amniocentesis--a procedure in which amniotic fluid and fetal cells are drawn out of the uterus for study--is now a widely accepted clinical practice, the panel found. They recommended that any pregnant woman age 35 or older should be advised about the possibility of undergoing amniocentesis (for detection of chromosomal abnormalities in the fetus). Other situations in which a pregnant woman should be offered the option of amniocentesis are:

  • if she has had a chromosomally abnormal child in the past;
  • if three or more of her past pregnancies have ended in miscarriages, or if her husband's previous wife experienced several miscarriages;
  • if she or her mate is known to have a chromosomal abnormality;
  • if there is a history of Down syndrome or some other chromosomal abnormality in her family or her spouse's family;
  • if she has male relatives with Duchenne muscular dystrophy or severe hemophilia, or if she is suspected of carrying some other harmful gene on one of her X chromosomes;
  • if her fetus is at a higher-than-usual risk for some hereditary error of metabolism detectable in utero; or
  • if her fetus is at increased risk for a neural tube defect.

 

Although a physician may inform a woman that she is at higher-than-usual risk of bearing a defective child and may acquaint her with the existence and uses of amniocentesis, the final decision to undergo the procedure must be her own, the panel stated. Health care professionals should provide patients with the information they need to make such decisions.

Echosonography (ultrasound) is a valuable technique for viewing the fetus and placenta prior to amniocentesis, according to the panel, which strongly recommended its use in this context. However, more clinical research will be required before ultrasound can be relied upon as a tool for diagnosis of physical defects in its own right.

Fetoscopy and fetal blood sampling remain experimental and are not ready for general use at this time, according to the panel. These techniques carry a higher risk to the fetus than do amniocentesis or echosonography, and should not be used in situations where safer methods would suffice.

Measurement of alpha-fetoprotein (AFP) in amniotic fluid is now an accepted practice for detecting neural tube defects in pregnancies at special risk for these disorders, the panel found. It may soon be possible to screen large numbers of pregnancies for neural tube defects by measuring AFP in the blood serum of obstetrical patients; however, this screening procedure cannot be recommended for wide use until pilot studies prove its efficacy.  

Predictors of Fetal Maturation

Ultrasonography and third-trimester amniocentesis are valuable, effective tools for determining fetal maturity in high-risk pregnancies and in other pregnancies where the baby may have to be delivered before term. In fact, appropriate use of these techniques can virtually eliminate the problems of prematurity and respiratory distress syndrome (RDS) following scheduled cesarean section, problems which have complicated 15 percent of such deliveries. However, these procedures should be used only when indicated, and should be studied further for possible long-range effects on both mother and fetus.

These were among the recommendations made by the Task Force on Predictors of Fetal Maturation, which discussed obstetrical techniques used to determine the age of a fetus and whether its lungs are mature enough to permit survival outside the uterus. Two such techniques are available: ultrasonography, and amniocentesis in the last three months of pregnancy. The amniotic fluid can be analyzed for certain components that indicate lung maturity by using either the L/S ratio test or the "shake test."

Panel members agreed that the potential benefits of both techniques in preventing premature deliveries far outweigh the costs and possible risks. However, because the long-range effects are unknown, the panel recommended against routine use of ultrasound for all pregnant women and cautioned that both ultrasound and third-trimester amniocentesis should be used only when indicated: in high-risk pregnancies, in cases where the woman has had previous cesarean sections, and in other cases where the physician thinks information on fetal maturity may be needed. Their specific recommendations were:

  • If the patient's obstetrical history suggests that a cesarean section may be necessary, a sonogram should be taken before the 26th week to measure the fetal biparietal diameter (head width), an indicator of fetal maturity. If there is still some question about the age of the fetus, a second sonogram should be taken early in the third trimester; together, the two measurements provide the baby's growth rate, and can be used to accurately estimate its age.
  • If the high-risk pregnant woman is not seen until later in pregnancy, ultrasound is not as accurate for judging fetal age and amniocentesis should be used to obtain reliable information on fetal lung maturity. (The panel recommended sonography to determine the position of fetus and placenta before amniocentesis.) Of the two tests that can be done on amniotic fluid--the L/S ratio test and the "shake test"--the panel said the L/S ratio is a more reliable indicator of fetal maturity. In both the L/S ratio and shake tests, there is an intermediate range of values which are hard to interpret and therefore unreliable predictors of whether a baby will develop RDS. However, with an L/S ratio of 2 or greater, there is a better than 99 percent chance that the baby will not have RDS.

 

Panel members pointed out that both methods require considerable expertise for accurate results--the shake test in particular is prone to inaccuracy when performed without caution. To minimize problems, the task force recommended post-graduate training in amniocentesis and ultrasonography for physicians with no experience in doing the procedures, and special care in performing the laboratory tests.

Suggesting directions for future research, task force members said there is a need for more accurate indicators of lung immaturity because of uncertain middle-range values in the L/S ratio test. They cited the "lung profile" and other measures as promising developments. Also, standards are needed for the manufacture of ultrasound machines and for both technical and professional proficiency in doing ultrasonography and amniocentesis.

The task force was chaired by Dr. Joseph Dancis, Chairman of the Department of Pediatrics, New York University School of Medicine.  

Predictors of Fetal Distress

Agreement was reached by the Task Force on Predictors of Fetal Distress that, at present, the use of electronic fetal monitoring (EFM) should be strongly considered in high risk patients. Among the specific circumstances which the task force felt could benefit from the use of electronic fetal monitoring are expected low birth weight, premature, postmature or intrauterine growth retarded babies; women with medical complications of pregnancy; the presence of meconium in the amniotic fluid; and situations where abnormal fetal heart rate is detected with a stethoscope (auscultation).

In the absence of identifiable risk factors, the task force found periodic auscultation* of the fetal heart rate to be an acceptable way to assess fetal condition for women at low risk for complications during labor and delivery. The panel pointed out that present data are inadequate to permit final conclusions, but found no evidence at present that electronic fetal monitoring reduces mortality or morbidity in low risk patients. Nonetheless, it recognized that under certain circumstances, mothers or physicians may choose to use EFM even in low risk situations.


* The panel defined periodic auscultation to include auscultation of the fetal heart every 15 minutes during the first stage of labor and every five minutes during the second stage. In either case, the fetal heart should be auscultated within 30 seconds of the end of a contraction.

In any case--whether or not EFM is employed--the task force emphasized that EFM should not be a substitute for clinical judgment. Any form of monitoring, the panel said, is only one measure of fetal status.

Since unexpected complications may arise during labor, the panel said that all hospitals and birthing centers providing maternity care should have the necessary trained staff and equipment to assess carefully the status of each fetus during labor and to take appropriate action.

The panel also strongly urged that fetal scalp blood pH determination be used as an adjunct to electronic fetal heart rate monitoring. Scalp blood testing provides additional information that may reduce monitoring-associated cesarean rates.

The task force cautioned that when electronic fetal monitoring is used, personnel should be well versed in the potential hazards. To minimize risk, the task force recommended that:

  1. Placement of the fetal scalp electrode and intrauterine pressure catheter should be performed very carefully and with the thorough understanding of the proper techniques to minimize risk of infection and injury to both mother and child.
  2. Prolonged supine position of the mother should be avoided.
  3. Maternal mobility should not be unnecessarily limited.
  4. Artificial rupture of the amniotic sac solely for internal electronic fetal monitoring should not be routine.

 

The task force recognized that electronic fetal monitoring may be considered intrusive by women who want a natural, family centered birth. For this reason, the group said that the proper use of EFM should include a discussion with the patient of her wishes, concerns, and questions about all forms of fetal monitoring. The panel recommended that women have the opportunity to discuss the subject during the course of prenatal care and again upon admission to the labor suite.

The task force also identified some specific areas where additional research is needed. These include:

  1. Research into the effects of hypoxia (decreased oxygen supply) on the fetus and newborn.
  2. Research to identify risk factors for fetal distress during birth, especially fetal distress which is amenable to EFM.
  3. Additional clinical trials of EFM in various categories of high risk patients to gather data on criteria for use, efficacy, and risk.
  4. Development of non-invasive methods of fetal monitoring.

 

The Task Force on Predictors of Fetal Distress was chaired by Dr. Frederick P. Zuspan, Professor and Chairman of the Department of Obstetrics and Gynecology at the Ohio State University College of Medicine.  

Task Force on Predictors of Hereditary Disease or Congenital Defects

Michael M. Kaback, M.D. (Chairman)
Professor of Pediatrics and Medicine
UCLA School of Medicine
Harbor-UCLA Medical Center
Torrance, California
Duane Alexander, M.D.
Project Officer, NICHD
Bethesda, Maryland
Robert L. Brent, M.D.
Professor and Chairman
Department of Pediatrics
Jefferson Medical College
Philadelphia, Pennsylvania
Barbara F. Crandall, M.D.
Associate Professor of Pediatrics and Psychiatry
UCLA Center for the Health Sciences
Los Angeles, California
Ezra Davidson, M.D.
Professor and Chairman
Department of Obstetrics and Gynecology
Charles R. Drew Postgraduate Medical School
Martin Luther King, Jr. General Hospital
Los Angeles, California
Carla Dowben, J.D.
Associate Professor of Obstetrics and Gynecology
University of Texas Southwestern Medical School
Texas Health Sciences Center
Dallas, Texas
Mitchell S. Golbus, M.D.
Associate Professor of Obstetrics and Gynecology and Pediatrics
University of California School of Medicine
San Francisco, California
Albert R. Jonsen, Ph.D.
Associate Professor of Bioethics
University of California School of Medicine
San Francisco, California
Maurice J. Mahoney, M.D.
Associate Professor of Pediatrics and Human Genetics
Yale University School of Medicine
New Haven, Connecticut
Godfrey Oakley, M.D.
Chief, Birth Defects Branch
Chronic Disease Division
Bureau of Epidemiology
Center for Disease Control
Atlanta, Georgia
Norman Scotch, Ph.D.
Professor and Chairman
Department of Sociomedical Sciences and Community Medicine
Professor of Anthropology
Boston University School of Medicine
Boston, Massachusetts
J. Michael Swint, Ph.D.
Associate Professor of Economics
University of Texas Health Sciences Center at Houston
School of Public Health
Houston, Texas
Elaine Whitelaw
Special Assistant to the President
National Foundation--March of Dimes
White Plains, New York
Laeitia Wotta
Task Force Assistant
Harbor-UCLA Medical Center
Torrance, California

Task Force on Predictors of Fetal Maturation

Joseph Dancis, M.D. (Chairman)
Professor and Chairman
Department of Pediatrics
New York University School of Medicine
Randall Bloomfield, M.D.
Director
Department of Obstetrics and Gynecology
Kings County Hospital Center
Paul Feeley, O. Carm.
Chairman
Health Systems Agency
District C, Manhattan
Louis Gluck, M.D.
Professor of Pediatrics
School of Medicine
University of California, San Diego
John Hobbins, M.D.
Professor of Obstetrics and Gynecology
Yale University School of Medicine
Angela R. Holder, LL.M.
Counsel for Medicolegal Affairs
Assistant Clinical Professor of Pediatrics (LAW)
Yale-New Haven Hospital
Rudy Sabbagha, M.D.
Associate Professor of Obstetrics and Gynecology
Director, Ultrasound Laboratory
Prentice Women's Hospital
Northwestern University Medical School
James Sorenson, Ph.D.
Associate Professor
Department of Sociomedical Sciences and Community Medicine
Boston University School of Medicine
Philip Sunshine, M.D.
Professor of Pediatrics
Stanford University
School of Medicine
Bruce Young, M.D.
Associate Professor of Obstetrics and Gynecology
Director, Division of Maternal-Fatal Medicine
New York University School of Medicine

Task Force on Predictors of Fetal Distress

Frederick P. Zuspan, M.D.
Task Force Chairman
Professor and Chairman
Department of Obstetrics and Gynecology
The Ohio State University College of Medicine
Columbus, Ohio
Lawrence Chik, Ph.D.
Assistant Professor
Department of Reproductive Biology
Case Western Reserve University
Department of Obstetrics and Gynecology
Cleveland Metropolitan General Hospital
Cleveland, Ohio
Bradford Gray, Ph.D.
Professional Associate
Institute of Medicine
Washington, DC
L. Stanley James, M.D.
Professor of Pediatrics
Columbia Presbyterian Medical Center
New York, New York
Barbara Katz, J.D.
Deputy General Counsel
Massachusetts Department of Public Health
Boston, Massachusetts
Phyllis Leppert, R.N., C.N.M., M.D.
Department of Obstetrics and Gynecology
Yale-New Haven Hospital
New Haven, Connecticut
Raymond R. Neutra, M.D., Dr. P.H.
Associate Professor
Division of Epidemiology UCLA School of Public Health
Los Angeles, California
Nigel Paneth, M.D., Ph.D.
Assistant Professor of Public Health and Pediatrics
Gertrude H. Sergievsky Center
Columbia University
New York, New York
Tabitha M. Powledge, M.S.
Research Associate for Genetics
Institute of Society, Ethics, and the Life Sciences
Hastings-on-Hudson, New York
Edward J. Quilligan, M.D.
Associate Vice President for Health Affairs
Professor of Obstetrics and Gynecology
University of Southern California School of Medicine
Los Angeles, California
Mortimer G. Rosen, M.D.
Professor
Department of Reproductive Biology
Case Western Reserve University
Director of Department of Obstetrics and Gynecology
Cleveland Metropolitan General Hospital
Cleveland, Ohio
Ama Saran, M.S.W.
Assistant to the Director
Black Child Development Institute
Washington, DC
Benjamin Silverman, M.D.
Pediatrician
Princeton, New Jersey
Judith Wagner, Ph.D.
Senior Research Associate
Urban Institute
Washington, DC

Conference Sponsors

National Institute of Child Health and Human Development

Fogarty International Center, NIH

Office of Medical Applications of Research, NIH

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