Child Policy Experts Answer Your Questions about Preventing Low Birth Weight
What does research tell us about preventing low birth weight?
Low birth weight (LBW) infants are those that are born weighing less than 5.5 pounds. Research shows that low birth weight infants face higher rates of infant mortality, developmental challenges, and long-term disabilities. The prevention of low birth weight infants is a serious public health challenge, and recent data suggest that the rate of LBW infants born in the United States has reached its highest level in almost 30 years.
In this Expert Perspectives feature, we invite you to ask three leading experts on child and maternal health your questions on the topic of preventing low birth weight.
About the Experts
José Cordero, MD, MPH
Garth Graham, MD, MPH
Carol Hogue, PhD, MPH
Below is a list of the question topics that were submitted to our experts. Follow the links below to read a particular question and answer, or scroll down the page to read them all.
Where should public health officials be focusing efforts and resources in order to have the greatest possible impact?
Is there any research on the relationship between the increase in labor intervention practices and low birth weight?
What steps can we take to address racial disparities in infant mortality and low birth weight??
In the case of extreme prematurity at birth, should a child's age be corrected on entry to school at 4.5 years of age?
The rate of low birth weight babies seems to be increasing in my community— what can I do to help turn things around?
Is 5.5 pounds the most useful weight for indicating elevated risk?
What things are most important to improve the chances that a teen has a healthy baby?
Should we be monitoring the oral health of expectant mothers in an effort to improve their overall health and reduce low birth weight babies?
Most low-income women have limited access to dental care. Should increased dental care be a regular part of prenatal care?
What percentage of low birth weight babies develop IVH? (IVH is intraventricular hemorrhage, bleeding in the brain)
How many low birth weight births are due to prematurity versus IUGR? (IUGR is intra-uterine growth retardation)
Questions and Answers
It is clear that the problem of low birth weight, like many other problems that we face in public health, is multifaceted and therefore has no simple answers. However, based on our current knowledge and understanding, is there a clear mandate as to where we at the district and county levels of public health should be focusing our efforts and resources in order to have the greatest possible impact?
Dr. Hogue: The question of where to focus public health efforts and resources in order to have the greatest possible impact on preventing low birth weight is both important and complex. Because we do not know how to prevent low birth weight once the mother is pregnant, the best approach may be to improve the health of the woman before she becomes pregnant. However, the impact of pre-conception (or well-woman) care on future pregnancy outcomes has yet to be determined. There are four notable exceptions, and it may be appropriate to focus resources on these, at least until the causes of low birth weight are better understood.
Three of the four exceptions pertain to timing of the next pregnancy. First, for all women, the optimum minimum inter-pregnancy interval (the time from the end of the first pregnancy to conception of the next child) is 18-23 months. Inter-pregnancy intervals of less than six months increase the risk of low birth weight in the next pregnancy by 40 percent and should be avoided for the health of the mother and of the baby. Second, for women who have delivered very low birth weight infants (<1,500 g), a few studies have demonstrated the effectiveness of targeted public health interventions to identify their particular needs and assist them through the baby's first two years for better health and support in postponing the next pregnancy. Third, for women who have given birth to the last baby they wish to have, assistance in preventing all future pregnancies will have a very large impact on the rate of low birth weight in the population. For example, in Georgia, prevention of all unwanted pregnancies would reduce the rate of low birth weight babies by 4 percent, the rate of cerebral palsy by 13 percent, and the rate of mental retardation by 14 percent. The fourth intervention is smoking prevention/cessation, which would reduce the rate of low birth weight by 6 percent in Georgia. 
To your knowledge, are any studies being conducted on the relationship between the increase in labor intervention practices and low birth weight? For example, inductions have become routine, along with the scheduling of deliveries vs. allowing a pregnancy to go full term.
Dr. Hogue: The Surgeon General has called for research into the causes of the rise in preterm delivery, including "late preterm" delivery of 34-36 completed weeks' gestation.  A small part of the increase is due to increased multi-fetal pregnancies related to assisted reproductive technologies, but most of the rise has yet to be explained. Possible causes include increased medical surveillance and intervention that lead to decisions to deliver, as well as an increase in labor induction or elective cesarean section at earlier gestational ages. 
For those conducting research into the relationship between increased delivery intervention practices and increased risk of low birth weight and prematurity, there is a need to distinguish between elective and indicated delivery interventions. For example, when a mother or preterm infant is in distress and delivery is inevitable or highly indicated to save the life of the mother or baby, the choice of cesarean section over vaginal delivery increases the infant's chance of survival and reduces the risk of some of the infant's major, long-term complications, perhaps even if the gestational age of the baby is as low as 22 weeks.  However, elective cesarean delivery or induced labor in the absence of known maternal or fetal risk appears to be on the rise. This raises the question of whether it is healthier for the low-risk mother and child not to intervene unless the gestational age is at least 39 completed weeks. Even with modern techniques for dating conception, there may be some uncertainty about the gestational age, and choosing an elective procedure to occur at an estimated 37-39 weeks may result in the delivery of a baby who is 34-36 weeks old. Errors in estimating gestational age are greater for obese women, and with obesity becoming epidemic in this country, these errors may be increasing.
The decision to intervene at term may have health consequences, even if the baby is born "early term" (37-38 weeks). During the last decade in the U.S., early-term births have increased by 14 percent for 37-week deliveries and 21 percent for 38-week deliveries. Among low-risk women with singleton births of 37 weeks' gestation or greater, the risk of serious neonatal pulmonary disease was highest for babies born at 37 weeks' gestation, compared with babies born after 39 completed weeks' gestation, and the risk of cesarean delivery was higher prior to 39 weeks' gestation.  This suggests that even low-risk "term" babies and mothers may be experiencing increased risks associated with an increase in cesarean deliveries when the gestational age is earlier than full term.
Dr. Cordero: We are looking at labor intervention practices in Puerto Rico as an explanation for the marked increase in preterm births on the island. Our rate of preterm births has increased from 11.4 percent in 1990 to 19.2 percent in 2004. During the same period we had an increase in cesarean sections from about 20 percent in 1990 to nearly 50 percent in 2004. That suggests a change in intervention practices.
Why has low birth weight risen in the last few years? Can it be explained by the increase in fertility treatments and the associated rise in multiple births?
Dr. Cordero: We know some of the reasons for the increase in low birth weight, but much more needs to be learned. One of the known factors contributing to the rise in low birth weight is assisted reproductive technology because it increases the number of multiple pregnancies. In the U.S., multiple pregnancies have increased from 2.3 percent of all pregnancies in 1990 to 3.4 percent in 2004. However, in the last decade, the rate of low birth weight among singletons has increased as well, so assisted reproductive technology is just part of the explanation. Women over 35 also have higher rates of low birth weight babies, and we have seen an increase in birth rates for women over 35. This trend also contributes only a small amount to the increase in low birth weight. Complications of pregnancy, such as eclampsia, preeclampsia, and diabetes are other contributors. In sum, low birth weight has increased in many groups, and while we can identify some of the factors that lead to this increase, there is still a lack of understanding about why we are observing this trend.
A number of researchers have indicated that disparities in birth outcomes exist for black infants regardless of the mother's education and socio-economic status. What course of action do you recommend that we, as health professionals, can take to address these disparities in infant mortality and low birth weight?
Dr. Hogue: Recommendations for reducing or eliminating health disparities for black infants include improving access to health services for the poor and underserved. Major health disparities exist between the middle class and the poor irrespective of race, and as black women continue to be overrepresented among the poor, it is imperative that efforts to improve the health of our most vulnerable populations be increased while at the same time striving to reduce their economic and social vulnerabilities. Health-related efforts include improving nutrition, providing nutrition education, caring for chronic conditions such as high blood pressure and diabetes, family planning, and providing other well-woman services with minimum barriers to access. For example, extending Medicaid eligibility to all women ages 15-44 who would qualify during pregnancy, irrespective of their pregnancy status, would be recommended.  Making sure that high-risk women deliver their babies in hospitals that can care for them and the babies is an extremely important and often-overlooked health intervention that can reduce racial disparities. 
As a researcher who was one of the first to note the continued disparities in health for middle-class black women , I have spent the last two decades attempting to understand this gap. The short answer is that no one yet knows the reason for it. When looking at the studies of college-educated black and white women, please remember that the studies considered education but not income when they compared black and white families. Well-educated black women are often the economic support for more people than those in their immediate family. As a result, they are more likely than white women of similar educational background to experience economic and other stresses during pregnancy. The "Hogue Hypothesis" (cf., the Barker Hypothesis for fetal origins of chronic diseases) is that adverse experiences in the womb (related to inter-generational effects of ongoing discrimination) and increased risks of adverse childhood experiences are related developmentally to stress-related hormones. These, in turn, affect a woman's ability to resist infection and handle pregnancy-related stress. 
Dr. Cordero: Yes, there is evidence of disparities in birth outcomes by race regardless of maternal education or socio-economic status. The biologic basis of this difference has not been determined, but it is very important to remember that known strategies for reducing low birth weight and preterm birth (access to quality prenatal care beginning in the first trimester, avoiding tobacco and alcohol, and good nutrition) measurably reduce the rate of those conditions among African-American infants. I would add that for women with a history of a previous preterm birth, the use of 17 hydroxyprogesterone is important for reducing the risk of preterm birth.
In the case of extreme prematurity at birth (<28 weeks gestation) and very low birth weight, do the experts agree that an infant's age should be corrected on entry to school at 4.5 years of age? If not, do they believe that all children should begin school at the same chronological age, or that some flexibility should be allowed for developmental differences, delays and/or disabilities?
Dr. Cordero: It is very important to determine preparedness to enter school at the kindergarten level. In my view, we should not try to develop general rules based on age of the child and history of low birth weight or preterm birth. Rather, I think we should ensure that children born with very low birth weight have the benefit of a robust early intervention program that addresses the functional deficits that the child may have with an appropriate early intervention plan that continues as needed upon school entry. We do face a major challenge with the limited availability of early intervention services, and that is something that every community needs to address. The American Academy of Pediatrics' Policy Statement on age terminology recommends the following terminology to describe the age of preterm infants: "Corrected age (weeks or months): chronological age reduced by the number of weeks born before 40 weeks of gestation; the term should be used only for children up to three years of age who were born preterm" (read the Policy Statement). Furthermore, the Centers for Disease Control recommend that growth charts be adjusted for prematurity and birth weight (read more about the growth charts).
I run an early childhood program in a primarily Mexican-American community. The rate of low birth weight babies seems to increase with the length of time women are in the U.S. Is there anything I can do to help turn things around?
Dr. Graham: Infant mortality rates for Hispanic subpopulations in 2002 ranged from 4.4 per 1,000 live births to 8.3 per 1,000 live births, compared to the non-Hispanic white infant mortality rate of 5.8 per 1,000 live births. The infant mortality rate for Mexican-American mothers aged 25-29 years was 4.7 per 1,000. However, in what has been called a "health paradox," foreign-born Hispanic mothers have lower rates of low birth weight, and foreign-born status appears to be a greater protective factor among women with less education. The reduction in low birth weight among Mexican-born women accounts for most of the foreign-born advantage, with foreign-born status reducing the risk of low birth weight by about 21 percent for Mexican-origin women.  The possible reasons for Mexican-American mothers doing better despite having poor access to prenatal care include better social support, immigration of primarily healthy women, and even possibly some dietary factors. It is possible that the women in your program lose some of that family support or have changes in their diet the longer they are in the U.S. I would certainly encourage the women in your program to continue to value their cultural traditions and habits and investigate any changes in family support or increased stress that they might be experiencing.
What percentage of low birth weight babies are born to women who haven't been told or instructed that they may be positive for group B strep or some other infection vs. virus? And is a check for group B strep and other infections mandatory for OB/GYNs? If so, when in the pregnancy is this checked?
Dr. Cordero: There are no good data on group B strep by presence of low birth weight. What we do know, based on the reports of the Centers for Disease Control, is that the rate of early-onset infection decreased from 1.7 cases per 1,000 live births (in 1993) to 0.5 cases per 1,000 live births (in 2000). The Centers for Disease Control have estimated that group B infections in infants have declined by 70 percent since the introduction of the recommendation of maternal cultures in late pregnancy followed by antibiotic treatment of the mother and the baby. They also report that the racial gap between blacks and whites narrowed by 75 percent in 1998.
The recommendation of the American Academy of Obstetrics and Gynecology is that pregnant women get a vaginal and rectal culture for group B strep at 35-37 weeks in gestation. Since nearly 12 percent of pregnancies are preterm and many end before 35 completed weeks, most babies born preterm and with low birth weight may not benefit from this prevention strategy.
Is 5.5 pounds the most useful weight for indicating elevated risk? What other weight might be considered? Or should we use prematurity instead of birth weight to indicate risk?
Dr. Cordero: It is important to be vigilant in identifying babies that may be at risk, and both low birth weight and prematurity are indicators of risk. The question is, at risk for what? Whether we select low birth weight as the marker of risk or preterm birth (less than 37 completed weeks of gestation), it is important to consider that these infants may be at highest risk for infections and neonatal complications such as hyperbilirubinemia and others. In terms of development, it is important to be on the lookout for early signs of developmental delay. Infants that are very low birth weight or very preterm should consistently be referred to early intervention programs.
We work with pregnant teens from low-income families. As part of our prenatal curriculum we address stress, nutrition, smoking, and alcohol and drug use and how these can affect the baby. Are there three things that you feel are most important to emphasize to improve the chances for a healthy baby?
Dr. Hogue: When working with pregnant teens, the most important thing to stress for a healthy baby is that this baby should be the only one for awhile. The pregnant teen is at higher-than-average risk of having another baby shortly after giving birth to this one. The next baby is at much higher risk of poor pregnancy outcomes if it is conceived sooner than 18 months to two years after the birth of the first baby. Also, the first baby may not get the attention it needs if the young mother is distracted by another baby. Providing the teen mother with long-lasting contraception at delivery or immediately postpartum is strongly recommended.
Stress management may be another important thing for a young, pregnant woman. She may be managing stress by using tobacco, drugs, or alcohol. Teaching her how to manage stress with more healthy behaviors may not only help her deliver a healthy baby but also help her care for her baby once it is born. Healthy stress reduction could include appropriate physical activity, cognitive behavioral therapy training, mindfulness meditation, and identification of appropriate supportive persons in her life.
As more and more teens are becoming obese, weight control during pregnancy is increasingly important to reduce risks to both mother and infant.
Studies have found that expectant mothers with periodontal disease (diseases of the tissues around teeth) are up to seven times more likely to deliver premature, low birth weight babies. It appears that oral health is overlooked when addressing many public health challenges—that we still don't associate the mouth with the rest of the body. Would it not be an effective prevention measure to put systems in place to improve/monitor the oral health of expectant mothers?
Dr. Graham: The link between periodontal disease and overall health is well established. Chronic periodontitis is an independent risk factor for hypertension and coronary artery disease. In fact, studies show that the severity of periodontitis is directly correlated to the severity of the coronary heart disease. There is a growing body of research looking at the association between periodontal disease and adverse birth outcomes. A study published in the New England Journal of Medicine  showed that treatment of periodontal disease in pregnant women improved periodontal disease and that it is safe, but did not significantly alter rates of preterm birth or low birth weight. That being said we do know that improving oral health is a good thing for the mother and subsequently for the child. Clinical trials presently underway will shed further light on the possible role of periodontal therapy in preventing adverse birth outcomes. Regardless, we must continue to emphasize good oral health as an integral part of our prevention measures, including monitoring the oral health of expectant mothers.
Most low-income women have limited access to dental care. Their oral health often worsens during pregnancy. The link between poor oral health and low birth weight/preterm births has been established. Should increased dental care be included as a regular part of prenatal care? Could OBs do an oral health screening similar to what pediatricians should do with children?
Dr. Graham: There is evidence that periodontal disease in pregnancy raises the risk of having a preterm or low birth weight birth. However, it is less clear that treating a mother's dental diseases during pregnancy prevents low birth weight or premature infants.  Good oral health remains an important part of overall preventative health activity including prenatal care. In the "Know What to Do for Life" Campaign on African American Infant Mortality led by the Office of Minority Health, we stress a comprehensive approach to prenatal care to make sure both mother and child remain healthy. It is important that this comprehensive approach is included in prenatal assessments and includes oral health screening.
As the parent (and an RN) of a child born prematurely at 30 weeks gestation and 4 pounds 7 ounces, I would really like to know how many of the children born below 5 pounds were premature?
Dr. Hogue: Most babies born below 5 pounds are premature. In the U.S. in 2005, about 92.2 percent of babies weighing less than 4.4 pounds were born premature. For babies weighing between 4.4 and 5.5 pounds at birth, about 56.2 percent were born premature. 
My daughter was born weighing less than five pounds. She was initially living in the neonatal intensive care unit (NICU) and had an apparent intraventricular hemorrhage (IVH; bleeding in the brain) grade II at 1+ weeks after birth. What percentage of low birth weight babies develop IVH?
Dr. Hogue: The proportion of low birth weight babies that develop an IVH of grade II or higher varies greatly by their gestational age and whether they are singleton or multiple births. In one large Australian study of babies born at less than 30 weeks' gestation who were carefully monitored for IVH at < six hours of age and again at seven and 28 days, 15 percent had a late IVH (68 percent grade II or higher).  This is consistent with other studies, on which the American Academy of Neurology and Child Neurology Society based its recommendation for routine ultrasound screening for infants born less than 30 weeks' gestation.  A recent report suggests that the cutoff for routine screening should be extended to 31 weeks' gestation, as 10 of 486 infants born between 30 and 33 weeks' gestation and monitored by routine ultrasounds were found to have IVH of grade II or higher. 
What is the relative fraction of low birth weight births due to prematurity and the fraction due to IUGR (intra-uterine growth retardation)? Is there a difference in risk for low birth weight children whose low birth weight is due to prematurity versus IUGR?
Dr. Hogue: Calculating the relative fraction of low birth weight births due to prematurity and the fraction due to IUGR depends on the definition of IUGR. Growth retardation is often estimated by the weight of the baby at birth. If the birthweight is below a certain cutoff for that gestational age, the baby is described as growth-retarded. For example, various investigators have determined the cutoff to be three, five, or 10 percent of the birthweight of all babies born at that gestational age. Therefore, depending on the definition, somewhere between three and 10 percent of premature babies are both premature and growth-retarded. Among preterm babies, extremely growth-retarded babies are at a greater risk of death compared with babies of similar gestation who weigh more. For example, in a German study of babies born less than 28 weeks' gestation, survival rates varied from 0 to 64 percent, depending on weight at birth (third percentile to appropriate weight for gestational age). 
Of course, not all low birth weight babies are premature. About 55 percent of low birth weight babies are born preterm and 45 percent are born full-term.  Full-term babies born weighing below the 10th percentile for their gestational age have an increased risk of neonatal death of 13 percent, compared with babies of similar gestational age weighing more than the 10th percentile. 
More About This Topic
Listed below are resources with more information on preventing low birth weight infants.
Promising Practices for Preventing Low Birth Weight
— Feb. 2009
Healthy Women, Healthy Babies
— June 2008
Kids Count Data on Low Birth Weight Babies
— May 2008
The Increasing Racial Disparity in Infant Mortality Rates: Composition and Contributors to Recent U.S. Trends
— Jan. 2008
Quick Reference Fact Sheets: Low Birthweight
America's Children: Key National Indicators of Well-Being (Low Birthweight)
Preterm Birth: Causes, Consequences, and Prevention
— July 2006
Recommendations to Improve Preconception Health and Health Care
— Apr. 2006
Low Birth Weight
— Spring 1995
PPN's Programs that Work
Visit PPN's Programs that Work section to read summaries of programs that have improved outcomes for low birth weight babies.
Listed below are sources that are cited in the experts' answers above.
1. For data on Georgia, Collier S, Hogue C. Modifiable Risk Factors for Low Birth Weight and Their Effect on Cerebral Palsy and Mental Retardation. Maternal and Child Health Journal 2007;11:65-71. Sources for the other data in this paragraph are available upon request. A paper covering these topics has been submitted for publication.
2. Galson SK. Surgeon General's Perspectives. Public Health Reports 2008;123:548-550
3. Engle WA, Kominiarek MA. Late Preterm Infants, Early Term Infants, and Timing of Elective Deliveries. Clinics in Perinatology 2008;35:325-41
4. Malloy MH. Impact of Cesarean Section on Neonatal Mortality Rates Among Very Preterm Infants in the United States, 2000-2003. Pediatrics 2008;122:285-292
5. Cheng YW, Nicholson JM, Nakagawa S, Bruckner TA, Washington AE, Caughey AB. Perinatal Outcomes in Low-Risk Term Pregnancies: Do They Differ by Week of Gestation? American Journal of Obstetrics & Gynecology. 2008;199:370.e1-7
6. Hogue CJR and Hargraves, MA. Preterm Birth in the African-American Community. Seminars in Perinatology 1995;19(40):255-262.
7. Hogue CJR, Vasquez C. Toward a Strategic Approach for Reducing Disparities in Infant Mortality. AJPH 2002;92:552-556.
8. Hogue CJR, Buehler JW, Strauss LT, Smith JC. Overview of the National Infant Mortality Surveillance (NIMS) Project—Design, Methods, Results. Public Health Reports March-April 1987; 102:126-137
9. Hogue CJR, Bremner JD. Stress Model for Research into Preterm Delivery Among African Americans. American Journal of Obstetrics & Gynecology 2005;192:S47-55
10. Acevedo-Garcia, D (1), Soobader MJ (1), Berkman, LF. Low Birthweight Among US Hispanic/Latino Subgroups: The Effect of Maternal Foreign-Born Status and Education. Social Science & Medicine 2007;65(12):2503-2516.
11. Michalowicz BS, Hodges JS, DiAngelis AJ, Lupo VR, Novak MJ, Ferguson JE, Buchanan W, Bofill J, Papapanou PN, Mitchell DA, Matseoane S, Tschida PA. Treatment of Periodontal Disease and the Risk of Preterm Birth. N Engl J Med 2006;355:1885
12. Khader YS and Ta'ani Q. Periodontal Diseases and the Risk of Preterm Birth and Low Birth Weight: A Meta-Analysis. Journal of Periodontology 2005;76(2): 161-165
13. Martin, JA, Hamilton, BE. Sutton PD, Ventura, SJ, Menacker F, Kirmeyer S and Munson ML, M.S Births: Final Data for 2005. National Vital Statistics Reports 2007;56(6). Table 32.
14. Osborn DA, Evans N, Kluckow M. Hemodynamic and Antecedent Risk Factors of Early and Late Periventricular/Intraventricular Hemorrhage in Premature Infants. Pediatrics 2003;112:33-39
15. Ment LR, Bada HS, Barnes P, et al. Practice Parameter: Neuroimaging of the Neonate. Report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society. Neurology 2002;58:1726-1738
16. Harris NJ, Palacio D, Ginzel A, Richardson CJ, Swischuk L. Are Routine Cranial Ultrasounds Necessary in Premature Infants Greater Than 30 Weeks Gestation? American Journal of Perinatology 2007;24:12-21
17. Bartels DB, Pets CF. The Search for Objective Criteria at the Limit of Viability. Neonatology 2008;93:193-6
18. Hediger ML, Overpeck MD, Ruan WJ, Troendle JF. Birthweight and Gestational Age Effects on Motor and Social Development. Paediatric and Perinatal Epidemiology 2002;16(1):33-46
19. Boulet SL, Alexander GR, Salihu HM, Kirby RS, Carlo WA. Fetal Growth Risk Curves: Defining Levels of Fetal Growth Restriction by Neonatal Death Risk. American Journal of Obstetrics & Gynecology 2006;195:1571-77