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Findings from the 1992-98 Patient Outcomes Research Team on Low Birthweight

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Clinical highlights of the Final Report of the Low Birthweight Patient Outcomes Research Team (PORT) are described below. Select to access the report's abstract or bibliography.

The Final Report (AHCPR Publication No. 98-N005) is available in limited quantities from the AHRQ Publications Clearinghouse (P.O. Box 8547, Silver Spring, MD 20907; Telephone: 800-358-9295). When supplies are exhausted, bound copies and microfiche can be purchased from the National Technical Information Clearinghouse (NTIS), Springfield, VA 22161 (Telephone: 703-605-6000 in Virginia or 800-553-6847 toll-free). To order, request NTIS Accession No. PB98-156565.

Antenatal Corticosteroid Therapy

In 1994, AHRQ's Patient Outcomes Research Team (PORT) on low birthweight collaborated with the National Institutes of Health's (NIH) consensus conference on the effectiveness of antenatal corticosteroids for fetal maturation on perinatal outcomes.

  • As a result of this collaboration, the PORT was able to confirm earlier research findings that antenatal corticosteroid therapy administered to a mother in preterm labor is highly effective in the prevention of mortality and disability in preterm infants.
  • In part due to the PORT's national dissemination efforts on the effectiveness of this therapy, the use of corticosteroids in preterm delivery has increased dramatically in many perinatal treatment centers and managed care facilities across the country—from approximately 30 percent of women who delivered prematurely prior to 1994 to almost 70 percent by 1996.
  • The PORT was able to validate the protective effects of antenatal corticosteroids when given alone or in combination with drugs to inhibit preterm labor, and also confirmed earlier findings that labor-inhibiting therapy without the protective effects of corticosteroids may be harmful in very preterm deliveries.

Bacterial Vaginosis and Other Infections

Working in collaboration with organizations such as the Centers for Disease Control and Prevention, the National Institute of Child Health and Human Development (NICHD), and the March of Dimes, the PORT team was able to:

  • Confirm the strong relationship between vaginal infection and preterm birth. Findings indicate that as many as 80 percent of early preterm births (i.e., 24 to 28 weeks' gestation) are associated with intrauterine infection.
  • Demonstrate that vaginal infections are strongly associated with preterm birth in women, accounting for 40 percent of the excess preterm birth in African American women.
  • Demonstrate that antibiotic treatment (e.g., with metronidazole and erythromycin, administered during the second trimester) for bacterial vaginal infection helps reduce the rate of premature delivery (less than 37 weeks' gestation) in women with bacterial vaginosis.
  • Demonstrate the cost-effectiveness of maternal screening and treatment strategies for the prevention of neonatal group B streptococcal sepsis.

Preeclampsia and Low-Dose Aspirin Therapy

Although findings from some clinical trials indicate that aspirin therapy is effective in reducing the risk of preeclampsia in pregnant women, other studies suggest that this therapy is associated with an increased risk of placental abruption. The PORT conducted several analyses to examine the data from these and other studies. The team's findings indicate that:

  • There is an association with aspirin therapy compliance as measured by a maintained decrease in serum thromboxane levels, resulting in improved pregnancy outcomes such as less preeclampsia, less premature rupture of membranes, fewer preterm births, higher mean birthweight, and fewer small-for-gestational-age births.
  • There appears to be no association between the risk of placental abruption and subsequent perinatal mortality and receiving preventive low-dose aspirin therapy.

Biochemical Predictors of Preterm Birth

PORT investigators, both in parallel and in collaboration with colleagues in NIH-funded studies examined biochemical markers or predictors of preterm birth. Findings from this work include:

  • Using data from serum samples of women in studies on risk factors for preterm delivery or term low birthweight, the PORT was able to conclude that the presence of interleukin-6 (IL-6) in the amniotic fluid is associated with an increase in spontaneous labor and may be useful as a predictor (or marker) for upper-genital-tract infection.
  • Other serum substances (e.g., plasma ferritin levels measured at 26 weeks' gestation) may be useful as predictors of spontaneous preterm birth.

Prevention-Based Findings

Through the use of secondary data analysis and a comprehensive review and synthesis of the literature, the PORT found that most intervention strategies aimed at the prevention or delay of preterm birth are not consistently effective. The specific practices determined to be ineffective for the prevention of premature birth are:

  • Bed rest.
  • Most labor-inhibiting drugs/agents.
  • Home uterine activity monitoring.
  • Intravenous (IV) hydration for premature labor.
  • Iron supplementation.
  • Risk scoring systems.

Additional PORT findings indicate that:

  • Poor pregnancy weight gain and low prepregnancy weight are associated with both preterm births and fetal growth restriction.
  • Drug, alcohol, and tobacco cessation during pregnancy helps lower the risk of preterm birth.
  • Zinc and folic acid supplementation are associated with increased birthweight and may reduce preterm birth. However, maternal weight appears to have an impact on the effectiveness of these nutrient supplements (i.e., thin women with low plasma levels of zinc benefit more from supplementation).

Neonatal Intensive Care

The PORT, in collaboration with the RAND Child Birth Management PORT and investigators from Stanford University, Palo Alto Institute of Research and Education, and UC San Francisco, analyzed the impact of perinatal centers and level of care on neonatal mortality in California during the early 1990s. The study found that risk-adjusted neonatal mortality was significantly lower for infant births that occurred in hospitals with high-volume, level III, neonatal intensive care units (NICUs). The study also concluded that costs for births at hospitals with level-III NICUs were no more expensive than for those infants born at other hospitals without level-III care facilities. Therefore, the concentration of high-risk deliveries in urban areas in a smaller number of hospitals that can provide level-III NICU care has the potential for decreasing neonatal mortality without increasing costs.

Future Research Priorities

The PORT concluded that research priorities should continue to concentrate on the search for factors that explain the specific causes of spontaneous preterm birth such as infection in the lower and upper reproductive tract, and on the funding of carefully designed trials of new practices that have strong theoretical potential to reduce the rate of low birthweight and prematurity. Long-term research is also needed to study the effects of low birthweight during child growth and development.

For More Information

A limited number of copies of the PORT's Final Report, entitled Low Birthweight in Minority and High-Risk Women (AHCPR Publication No. 98-N005), are available from the AHRQ Publications Clearinghouse. To order the Final Report or additional copies of this Clinical Highlight, contact:

AHRQ Publications Clearinghouse
P.O. Box 8547
Silver Spring, MD 20907
Telephone: 800-358-9295 (calls taken 24 hours a day, 7 days a week)

When supplies of the final report are exhausted, bound copies and microfiche can be purchased from the National Technical Information Service (NTIS) of Springfield, Virginia. The NTIS accession number used for ordering purposes is PB98-156565. Telephone NTIS at 703-605-6000 (within Virginia) or 800-553-6847 (toll-free) for price and ordering information.

Select to access online versions of the PORT's abstract and cumulative bibliography from the final report.

AHRQ Publication No. 00-P010
Replaces AHCPR Publication No. 99-P005
Current as of January 2000


The information on this page is archived and provided for reference purposes only.


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