In 2004, 12.5 percent of births in the United States were preterm; that is, born at less than 37 completed weeks of gestation. This rate has increased steadily in the past decade. There are significant, persistent, and very troubling racial, ethnic, and socioeconomic disparities in the rates of preterm birth. The highest rates are for non-Hispanic African Americans, and the lowest are for Asians or Pacific Islanders. In 2003, the rate for African-American women was 17.8 percent, whereas the rates were 10.5 percent for Asian and Pacific Islander women and 11.5 percent for white women. The most notable increases from 2001 to 2003 were for white non-Hispanic, American Indian, and Hispanic groups.

Infants born preterm are at greater risk than infants born at term for mortality and a variety of health and developmental problems. Complications include acute respiratory, gastrointestinal, immunologic, central nervous system, hearing, and vision problems, as well as longer-term motor, cognitive, visual, hearing, behavioral, social-emotional, health, and growth problems. The birth of a preterm infant can also bring considerable emotional and economic costs to families and have implications for public-sector services, such as health insurance, educational, and other social support systems. The annual societal economic burden associated with preterm birth in the United States was at least $26.2 billion in 2005. The greatest risk of mortality and morbidity is for those infants born at the earliest gestational ages. However, those infants born nearer to term represent the greatest number of infants born preterm and also experience more complications than infants born at term.

Preterm birth is a complex cluster of problems with a set of overlapping factors of influence. Its causes may include individual-level behavioral and psychosocial factors, neighborhood characteristics, environmental exposures, medical conditions, infertility treatments, biological factors, and genetics. Many of these factors occur in combination, particularly in those who are socioeconomically disadvantaged or who are members of racial and ethnic minority groups.

The current methods for the diagnosis and treatment of preterm labor are currently based on an inadequate literature, and little is know about how preterm birth can be prevented. Treatment has been focused on inhibiting contractions. This has not reduced the incidence of preterm birth but has delayed delivery long enough to allow the administration of antenatal steroids and transfer of the mother and fetus to a hospital where they may receive appropriate care. These interventions have reduced the rates of perinatal mortality and morbidity. Although improvements in perinatal and neonatal care have significantly improved the rates of survival for infants born preterm, these infants remain at risk for a host of acute and chronic health problems. Therapies and interventions for the prediction and the prevention of preterm birth are thus needed.

Upon review of the literature assessing the causes and consequences of preterm birth, the diagnosis and treatment of women at risk for preterm labor, and treatments for infants born preterm, the committee proposes a research agenda for investigating the problem of preterm birth that is intended to help focus and direct research efforts. Priority areas are: (1) the establishment of multidisciplinary research centers; (2) improved research in three areas including better definition of the problem of preterm birth with improved data, clinical and health services research investigations, and etiologic and epidemiologic investigations; and (3) the study and informing of public policy. The committee hopes that its efforts will help provide a framework for working toward improved outcomes for children born preterm and their families.

Contents

• The National Academies
• Committee on Understanding Premature Birth and Assuring Healthy Outcomes
• Board on Health Sciences Policy
• Reviewers
• Preface
• Acknowledgments
• Summary
  • STUDY CHARGE
  • APPROACH TO THE PROBLEM
  • AN AGENDA TO INVESTIGATE PRETERM BIRTH
  • CONCLUDING REMARKS
• 1. Introduction
  • CONTEXT AND CHARGE TO THE COMMITTEE
  • PREVIOUS REPORTS ADDRESSING PRETERM BIRTH AND LOW BIRTH WEIGHT INFANTS
  • RECURRING THEMES
  • THE PROBLEM OF PRETERM BIRTH
  • CONTENT AND STRUCTURE OF THE REPORT
• I. Measurement
  • 2. Measurement of Fetal and Infant Maturity
    • ABSTRACT
    • DEFINITION OF PRETERM BIRTH
    • MEASUREMENT OF GESTATIONAL AGE
    • MEASUREMENT OF FETAL AND INFANT MATURATION
    • HETEROGENEITY OF THE PRETERM INFANT POPULATION
    • IMPLICATIONS FOR PUBLIC HEALTH AND RESEARCH
    • Clarifying Mortality Rates
    • CONCLUSIONS
  • Recommendations
• II. Causes of Preterm Birth
  • 3. Behavioral and Psychosocial Contributors to Preterm Birth
    • ABSTRACT
    • BEHAVIORAL INFLUENCES ON PRETERM BIRTH
    • Alcohol Use
    • Nutrition
    • Employment
    • Physical Activity
    • Sexual Activity
    • Douching Before and During Pregnancy
    • PSYCHOSOCIAL FACTORS AND PRETERM BIRTH
    • SUMMARY AND FUTURE DIRECTIONS FOR RESEARCH
  • 4. Sociodemographic and Community Factors Contributing to Preterm Birth
    • ABSTRACT
    • SOCIODEMOGRAPHIC FACTORS
    • MARITAL STATUS AND COHABITATION
    • COMMUNITY FACTORS
    • CONCLUSION
  • 5. Medical and Pregnancy Conditions Associated with Preterm Birth
    • ABSTRACT
    • MEDICAL ILLNESSES AND CONDITIONS
    • INFERTILITY TREATMENTS AND PRETERM BIRTH
    • RISK FOR MULTIPLE GESTATIONS ARTs
  • 6. Biological Pathways Leading to Preterm Birth
    • ABSTRACT
    • MECHANISMS OF PARTURITION
    • PATHWAYS TO SPONTANEOUS PRETERM PARTURITION
    • PREMATURE RUPTURE OF MEMBRANES
    • ANIMAL MODELS FOR PRETERM BIRTH AND NEONATAL SEQUELAE
  • 7. Role of Gene-Environment Interactions in Preterm Birth
    • ABSTRACT
    • EVIDENCE OF GENETIC INFLUENCES ON PRETERM DELIVERY
    • GENE-ENVIRONMENT INTERACTIONS
    • EPIGENETICS
    • PROTEOMICS
    • GENETICS AND RACIAL-ETHNIC DISPARITIES IN PRETERM BIRTH RATES
    • METHODOLOGICAL ISSUES
    • CONCLUSION
  • 8. The Role of Environmental Toxicants in Preterm Birth
    • ABSTRACT
    • EXPOSURE ASSESSMENT CHALLENGES
    • AIR POLLUTION
    • AGRICULTURAL CHEMICALS
    • POLYCHLORINATED BIPHENYLS
    • DIOXIN
    • CHLORINATION DISINFECTION BY-PRODUCTS
    • ENVIRONMENTAL TOBACCO SMOKE
    • METALS AND METALLOIDS
    • PATERNAL EXPOSURES TO ENVIRONMENTAL TOXICANTS
    • RACIAL DISPARITIES IN ENVIRONMENTAL EXPOSURES
    • BIOLOGICAL MECHANISMS
    • CONCLUSIONS
  • Recommendations
• III. Diagnosis and Treatment of Preterm Labor
  • 9. Diagnosis and Treatment of Conditions Leading to Spontaneous Preterm Birth
    • ABSTRACT
    • PREDICTION AND ASSESSMENT OF RISK OF PRETERM BIRTH
    • CLINICAL PREDICTORS
    • PREVENTION STRATEGIES
    • Medical Interventions
    • Other Prophylactic Medications
    • Surgical Interventions
    • Nonmedical Interventions
    • DIAGNOSIS AND TREATMENT OF PRETERM LABOR
    • Diagnosis of Preterm Labor
    • FUTURE DIRECTIONS
  • Recommendations
• IV. Consequences of Preterm Birth
  • 10. Mortality and Acute Complications in Preterm Infants
    • ABSTRACT
    • MORTALITY
    • COMPLICATIONS OF PRETERM BIRTH
    • NEURODEVELOPMENTAL SUPPORT
    • VARIATIONS IN NEONATAL COMPLICATION RATES
    • CONCLUSIONS
  • 11. Neurodevelopmental, Health, and Family Outcomes for Infants Born Preterm
    • ABSTRACT
    • NEURODEVELOPMENTAL DISABILITIES
    • Motor Impairment
    • Cognitive Impairment
    • Visual Impairment
    • Hearing Impairment
    • Behavioral and Social-Emotional Problems
    • Severity of Disability
    • Disability in Late Preterm or Near-Term Infants
    • Functional Outcomes
    • Summary
    • FACTORS THAT INFLUENCE NEURODEVELOPMENTAL OUTCOMES
    • HEALTH AND GROWTH
    • IMPACT OF PRETERM BIRTH ON FAMILIES
    • POST-NICU DISCHARGE INTERVENTIONS
    • CONCLUSION
  • 12. Societal Costs of Preterm Birth
    • ABSTRACT
    • COST-OF-ILLNESS METHODOLOGY APPLIED TO PRETERM BIRTH
    • MEDICAL CARE COSTS DUE TO PRETERM BIRTH
    • EARLY INTERVENTION SERVICES
    • SPECIAL EDUCATION COSTS
    • INDIRECT COSTS: HOUSEHOLD AND LABOR MARKET PRODUCTIVITY
    • FAMILY COSTS
    • ECONOMIC EVALUATION OF INTERVENTIONS TO REDUCE PRETERM BIRTH AND ITS CONSEQUENCES
    • CONCLUSIONS
  • Recommendations
• V. Research and Policy
  • 13. Barriers to Clinical Research on Preterm Birth and Outcomes for Preterm Infants
    • ABSTRACT
    • CAREER DEVELOPMENT
    • RESEARCH FOR DRUG DEVELOPMENT
    • FUNDING FOR RESEARCH ON PRETERM BIRTH
    • ETHICAL AND LIABILITY ISSUES IN REPRODUCTION RESEARCH
    • LEADERSHIP CHALLENGES AND NEEDS
  • 14. Public Policies Affected by Preterm Birth
    • ABSTRACT
    • PUBLIC PROGRAM EXPENDITURES ASSOCIATED WITH PRETERM BIRTH
    • ROLE OF PUBLIC POLICY AND PROGRAMS IN REDUCING PRETERM BIRTH AND ENSURING HEALTHY OUTCOMES
  • Recommendations
  • 15. A Research Agenda to Investigate Preterm Birth
    • I ESTABLISH MULTIDISCIPLINARY RESEARCH CENTERS
    • II PRIORITY AREAS FOR RESEARCH
    • Conduct Etiologic and Epidemiologic Investigations
    • III STUDY AND INFORM PUBLIC POLICY
• References
• Appendixes
  • A Data Sources and Methods
  • B Prematurity at Birth: Determinants, Consequences, and Geographic Variation
  • C A Review of Ethical Issues Involved in Premature Birth
  • D A Systematic Review of Costs Associated with Preterm Birth
  • E Selected Programs Funding Preterm Birth Research
  • F Committee and Staff Biographies

This study was supported by Contract No. N01-OD-4-2139, Task Order No. 145 between the National Academy of Sciences and the National Institute for Child Health and Human Development, Centers for Disease Control and Prevention, Health Resources and Services Administration, Environmental Protection Agency, and NIH Office of Research on Women’s Health; and contracts with the March of Dimes, Burroughs Wellcome Fund, American College of Obstetricians and Gynecologists, American Society for Reproductive Medicine, and the Society for Maternal-Fetal Medicine. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the organizations or agencies that provided support for this project.

NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.