PPN Issue Briefs
Promising Practices for Preventing Low Birth Weight
This summary provides a concise overview of research-based information related to preventing low birth weight. For more in-depth information about this topic, please consult the references listed below or see additional PPN resources, shown at the right.
What is low birth weight?
Low birth weight (LBW) is defined as birth weight under 5.5 pounds. While this particular cutoff point is considered to be somewhat arbitrary, it is clear that lower birth weights are associated with worse outcomes over the entire life course. Lower birth weight babies are more likely to die in the first year of life and suffer from chronic health conditions, such as asthma and high blood pressure, as well as compromised cognitive development. The disadvantage from low birth weight persists into adulthood, with lower birth weight individuals scoring lower on IQ tests at age 18, attaining less education, and earning less income than their peers. 
The percentage of births that are low birth weight is one of the most widely used indicators of population-level health around the globe, and reducing LBW is a common public health policy objective.  One estimate suggests that raising birth weight by even half a pound for a LBW infant saves an average of more than $28,000 in first-year medical costs alone.  In 2005, about one out of every 12 births in the United States was LBW. 
Prematurity and fetal growth retardation can both lead to low birth weight. In the case of prematurity, a normally developing fetus is delivered before reaching full gestation and is generally below average weight. In the case of growth retardation, the fetus has lagged in its growth and even a full-term baby may be low birth weight. Babies whose LBW is due to growth retardation are generally believed to be at higher risk for poor outcomes.  Slightly over half of LBW is attributable to prematurity. 
The complex interaction of a constellation of individual, social, community, and environmental factors contributes to LBW. The factors listed below raise the risk of delivering a LBW baby.
Risk Factors Associated with Low Birth Weight 
- Maternal education less than high school
- Teen mother (less than 20 years old)
- Low family income
- Cigarette smoking, alcohol consumption, and/or cocaine use during pregnancy
- Multiple birth
- Short maternal stature or low maternal prepregnancy weight
- History of infertility
- Single mother
- No or inadequate prenatal care
- Perceived maternal stress
- Closely spaced pregnancies
- African-American mother
- Older mother (more than 35)
- Total pregnancy weight gain less than 22 pounds or poor nutrition
- Sexually transmitted diseases or other infections
- Mother has hypertension or diabetes
- Previous delivery of a LBW baby
- Motherís physical abnormalities or anomalies
- Occupational and environmental exposures
- Physical harm from injuries
- Sexual activity during late pregnancy
- Unwanted pregnancy
What are the current trends in LBW in the United States?
Over the last decade and a half, there have been one-third fewer teen pregnancies,  a lower rate of expectant mothers smoking, and more pregnant women getting prenatal care,  so one might expect that the rate of LBW would be declining. It is not, however: The fraction of babies born with LBW has been growing since 1990 (see Figure 1).
Possible explanations for this trend might include more multiple births as a result of fertility treatments and a greater fraction of older mothers, both of which tend to be associated with babies born at lower weights.  However, the rates of LBW have grown across nearly all groups—young and old mothers, white and nonwhite births, singleton and multiple births —and there is a lack of consensus regarding what explains the gradual increase in the prevalence of LBW.
Figure 1. Percentage of Births That Are Low Birth Weight, by Year
SOURCES: U.S. National Center for Health Statistics, National Vital Statistics Reports (NVSR),
Vol. 55, No. 1, September 29, 2006, and Vol. 55, No. 11, December 28, 2006.
Another persistent pattern in LBW that has alluded explanation is that African American babies are much more likely to be born LBW even after controlling for factors that explain many individual differences in birth weight, such as maternal education or family income. In 2005, 14 percent of non-Hispanic black babies were born with LBW, compared with 7.3 percent of non-Hispanic white babies and 6.9 percent of Hispanic babies.  Current research is examining the role of health care access and delivery, exposure to cumulative stress, and other potential factors that may account for these differences. 
What works to prevent LBW?
The staples of LBW prevention for decades have been prenatal care and smoking cessation. However, a recent review article that examined strategies for addressing the primary two reasons for LBW concluded that "neither preterm birth nor [intrauterine growth restriction] can be effectively prevented by prenatal care in its present form."  Moreover, the authors of this article rated smoking cessation as only "modestly effective." Similarly, a 2007 Institute of Medicine committee on preterm births declared that "there is no test that can accurately predict a preterm birth and little is known about how a preterm birth can be prevented." 
These assessments of the state of LBW prevention strategies have led to calls for more and better research and questions about what practitioners and policymakers can do now to improve LBW outcomes. Given the complexity of the causes of LBW, it is not surprising that promising approaches to LBW prevention include a spectrum of strategies. The prevailing approach to preventing LBW generally focuses on influencing modifiable individual-level factors, such as maternal obesity or stress. Currently, the most promising approaches to reducing LBW appear to be the following: 
- Improving women's general health over the life cycle. This includes improving health conditions such as diabetes, asthma, mental illness, and others that are related to poor birth outcomes.
- Helping women improve fertility planning to reduce unwanted pregnancies and space births at least 18 months apart.
- Encouraging women to engage in healthy preconception behaviors like taking folic acid supplements and identifying pregnancies in a timely fashion.
- Improving the health behaviors of pregnant women, including smoking cessation, reducing or quitting drug use, and appropriate weight gain.
- Screening pregnant women for certain medical conditions, such as infections or physical abnormalities.
In the longer term, additional research about effective interventions and changes in the social determinants of health will be the engines that generate further improvements in birth outcomes.
1. Sandra J. Black, Paul J. Devereux, and Kjell Salvanes, "From the Cradle to the Labor Market? The Effect of Birth Weight on Adult Outcomes," Quarterly Journal of Economics, Vol. 122, No. 1, 2007, pp. 409-439. G. Valsmakis et al., "Causes of Intrauterine Growth Restriction and the Postnatal Development of the Metabolic Syndrome," Annals of the New York Academy of Sciences, Vol. 1092, 2006, pp. 138-147. N. S. Paneth, "The Problem of Low Birth Weight," The Future of Children, Vol. 5, No. 1, 1995, pp. 19-34.
2. Annie E. Casey Foundation, 2008 Kids Count Data Book: State Profiles of Child Well-Being, Baltimore, Md.: Annie E. Casey Foundation, 2008. U.S. Department of Health and Human Services, Healthy People 2010: Understanding and Improving Health, 2nd ed., Washington, D.C.: U.S. Government Printing Office, November 2000. World Health Organization, 2008, Core Health Indicators, 2008. As of January 29, 2008: http://www.who.int/whosis/database/core/core_select.cfm
3. J. A. Rogowski, "Cost-Effectiveness of Care for Very Low Birth Weight Infants," Pediatrics, Vol. 102, No. 1, 1998, pp. 35-43.
4. Centers for Disease Control and Prevention, VitalStats, Hyattsville, Md.: National Center for Health Statistics, last modified September 10, 2008. As of January 29, 2008: http://www.cdc.gov/nchs/vitalstats.htm
5. D. B. Bartels, C. F. Pets, "The Search for Objective Criteria at the Limit of Viability," Neonatology, Vol. 93, 2008, pp. 193-196. Richard E. Behrman, Adrienne Stith Butler, eds., Preterm Birth: Causes, Consequences and Prevention, Institute of Medicine, Committee on Understanding Premature Birth and Assuring Healthy Outcomes, Washington, D.C.: National Academies Press, 2007.
6. M. L. Hediger, M. D. Overpeck, W. J. Ruan, J. F. Troendle, "Birthweight and Gestational Age Effects on Motor and Social Development," Pediatric and Perinatal Epidemiology, Vol. 16, No. 1, 2002, pp. 33-46.
7. V. R. Chomitz, L.W.Y Cheung, and E. Lieberman, "The Role of Lifestyle in Preventing Low Birth Weight," The Future of Children, Vol. 5 No. 1, 1995, pp. 121-138; Richard E. Behrman, Adrienne Stith Butler, eds., Preterm Birth: Causes, Consequences and Prevention, Institute of Medicine, Committee on Understanding Premature Birth and Assuring Healthy Outcomes, Washington, D.C.: National Academies Press, 2007.
8. Centers for Disease Control and Prevention, VitalStats, Hyattsville, Md.: National Center for Health Statistics, last modified September 10, 2008. As of January 29, 2008: http://www.cdc.gov/nchs/vitalstats.htm
9. Joyce A. Martin, Hsiang-Ching Kung, T. J. Mathewsa, Donna L. Hoyert, Donna M. Strobino, Bernard Guyer, Shae R. Sutton, "Annual Summary of Vital Statistics, 2006," Pediatrics, Vol. 121, No. 4, pp. 788-801, 2008.
10. Martin et al., 2008.
11. J. A. Martin, B. E. Hamilton, P. D. Sutton, et al., "Births: Final Data for 2005," National Vital Statistics Reports, Vol. 56, No. 6, 2007, pp. 1-103.
12. Centers for Disease Control and Prevention, VitalStats, Hyattsville, Md.: National Center for Health Statistics, last modified September 10, 2008. As of January 29, 2008: http://www.cdc.gov/nchs/vitalstats.htm
13. C.J.R. Hogue, J. D. Bremner, "Stress Model for Research into Preterm Delivery Among African Americans," American Journal of Obstetrics & Gynecology, Vol. 192, 2005, pp. S47-S55.
14. M. C. Lu, V. Tache, G. R. Alexander, M. Kotelchuck, N. Halfon, "Preventing Low Birth Weight: Is Prenatal Care the Answer?" Journal of Maternal-Fetal and Neonatal Medicine, Vol. 13, No. 6, June 1, 2003, pp. 362-380.
15. Richard E. Behrman, Adrienne Stith Butler, eds., Preterm Birth: Causes, Consequences and Prevention, Institute of Medicine, Committee on Understanding Premature Birth and Assuring Healthy Outcomes, Washington, D.C.: National Academies Press, 2007.
16. Behrman and Stith Butler, 2007. Centers for Disease Control and Prevention, "Recommendations to Improve Preconception Health and Heath Care, a Report of the CDC/ATSDR Preconception Care Work Group and the SelectPanel on Preconception Care," Morbidity and Mortality Weekly Report, 2006, Vol. 55, No. RR-6). S. Collier, C. Hogue, "Modifiable Risk Factors for Low Birth Weight and Their Effect on Cerebral Palsy and Mental Retardation," Maternal and Child Health Journal, Vol. 11, 2007, pp. 65-71. V. R. Chomitz, L.W.Y. Cheung, E. Lieberman, "The Role of Lifestyle in Preventing Low Birth Weight," The Future of Children, Vol. 5, No. 1, 1995, pp. 121-138. A. Conde-Agudelo, A. Rosas-Bermudez, A. C. Kafury-Goeta, "Birth Spacing and Risk of Adverse Perinatal Outcomes: A Meta-Analysis," Journal of the American Medical Association, Vol. 295, No. 15, 2006, pp. 1809-1823.
About this Issue Brief
This document was produced by the Promising Practices Network (PPN) on Children, Families and Communities and is published online as part of PPN's Issue Brief series. This Issue Brief is available at the following URL: http://www.promisingpractices.net/briefs/briefs_lowbirthweight.asp
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