Journal Issue: School Readiness: Closing Racial and Ethnic Gaps Volume 15 Number 1 Spring 2005
Child health policymakers and practitioners have implemented many programs both to prevent low birth weight and to improve the life chances of low birth weight babies, especially in the areas of school readiness and achievement. To the extent that the programs succeed, they could help narrow racial gaps in school readiness by as much as 3 to 4 percent, as noted.
Preventing Low Birth Weight
Recognizing the close links between low birth weight and socioeconomic status, policymakers have emphasized a strategy of expanding prenatal care eligibility and services for poor pregnant women. The expansion of Medicaid eligibility and outreach to pregnant women in the late 1980s and early 1990s increased access to prenatal care, improved services, and helped more women begin care earlier in their pregnancies.97 Rates of both early and adequate use of prenatal care increased substantially between 1981 and 1998 for both blacks and whites, and, except for some groups of young mothers, racial disparities in the use of prenatal care decreased.98 In 2000, 85.0 percent of white mothers and 74.3 percent of black mothers who gave birth in the United States began prenatal care in the first trimester of pregnancy; 3.3 percent of white mothers and 6.7 percent of black mothers had late or no prenatal care.99 Nevertheless, the U.S. rate of low birth weight, even for singletons, has not declined— perhaps owing in part to the declining rate of fetal mortality—and remains higher than that of most other developed countries.
It is difficult to ascertain the effectiveness of prenatal care in reducing low birth weight. Randomized controlled trials—the gold standard in such research—are rarely feasible because of ethical concerns about depriving women of care. In a rare randomized trial, Lorraine Klerman and colleagues compared augmented and standard prenatal care provided to Medicaid-eligible African American women. The augmented care improved women's satisfaction with care and knowledge about risk conditions but did not reduce the rate of low birth weight.100
Studies other than randomized controlled trials face several methodological challenges, including selection bias. With favorable selection, women with the best expected outcomes are the most likely to seek prenatal care and to do so early, so the estimated effect of care could be overstated. With adverse selection, women with the worst expected outcomes are most likely to seek care and to do so early, so the estimated effect of care could be understated.
Research on the effects of expanded Medicaid eligibility and services on birth weight has produced mixed findings. Collectively, studies indicate only modest positive effects, stronger among blacks than whites.101 One reason for the inconsistent findings may be that prenatal care varies widely—in the services and interventions offered, in the settings in which it is provided, and in quality. Moreover, interventions targeted at low-income families often lose clients by attrition, and programs are not always implemented as intended. Two recent studies have found that legislated changes in providers—one through hospital desegregation in Mississippi in the Civil Rights era and another, more recently, through changes in Medicaid hospital payments in California—reduced rates of low birth weight among African American children.102
Unquestionably, prenatal medical care can benefit certain mothers and their babies enormously. All women, pregnant or not, should get preventive and regular medical care. But standard prenatal care cannot be expected to improve aggregate birth outcomes because most treatable medical conditions during pregnancy affect only a small proportion of women.103 A recent comprehensive review found no evidence that prenatal educational or psychosocial services, home visiting programs, or any medical interventions, even those to prevent infections, prevented either preterm birth or fetal growth retardation.104 Researchers have recently found that progesterone supplementation reduces preterm birth among women who have had a previous preterm birth, but studies of its effectiveness and safety are still ongoing.105 One promising way to reduce aggregate rates of low birth weight is to reduce smoking.106 Another is through better nutrition. Three recent studies found that participation in the Supplemental Nutrition Program for Women, Infants, and Children (WIC) raised birth weight.107
The point is not that prenatal care programs have no positive effects. Rather, variations in content, implementation, or compliance make it difficult to pinpoint their effects. They may improve maternal health by connecting mothers to the health care system. They may reduce fetal death. Those that include family planning and other psychosocial services that could affect future fertility and prenatal behaviors could, in turn, improve maternal or infant health and increase the use of pediatric care. At the minimum, women of childbearing age should receive standard medical care beginning well before pregnancy, as well as smoking cessation and nutritional services as needed. But prenatal care—even enhanced care—will not automatically offset a lifetime of maternal health disadvantages.
Improving Cognitive Outcomes Associated with Low Birth Weight
Practitioners have established many early intervention programs to enhance the cognitive development of low birth weight infants and to improve their school readiness. Many programs pertaining to low birth weight and school readiness have been designed as randomized clinical trials, making them relatively straightforward to evaluate.
A broad review of such interventions found modest success overall, with the most effective programs involving parents as well as children.108 One such “two-generation” intervention, the Infant Health and Development Program (IHDP), targeted low birth weight premature infants at eight sites. In the treatment group, 377 children received two years of high-quality center-based care at ages two and three. Family support, including home visits and parent group meetings, was also provided. The 608 children in the control group received none of these services. Both groups received the same medical care.
Many researchers have examined the readiness- related effects, both cognitive and behavioral, of the IHDP. Jeanne Brooks-Gunn and her coauthors found that the mean IQ of the intervention group at age three was 93.6, while that of the control group was 84.2; and that heavier low birth weight infants benefited more than lighter infants (those weighing less than 2,000 grams).109 For both black and white sub-samples, children whose mothers had a high school education or less gained more from the intervention than those whose mothers had attended college, with the latter showing no significant enhancement in IQ scores at age three.110 Several studies found that the intervention improved cognitive scores at ages twenty-four months and thirty-six months, and one found lower (more favorable) behavior problem scores at twenty-four and thirty-six months.111 Children who had large gains on IQ score, cognitive skills, school achievement, and behavior at age three, however, generally did not sustain the gains at age eight, although the heavier low birth weight intervention group still outscored the control groups on measures of cognition and school achievement.112 And another study found that children at age eight who had attended the program for at least 400 days scored 7 to 10 points higher on IQ tests than those in the control group. Again, effects were greater for the heavier low birth weight infants (about 14 points) than for the lighter low birth weight infants (about 8 points).113
Combining home visits with hospital-based intervention also appears to be effective in enhancing the cognitive function of low birth weight children. In a randomized controlled trial of an intervention in Vermont that provided four home visits and seven hospital sessions, the experimental low birth weight group scored higher on several standardized tests at age seven than did a control group that received no treatment; differences in outcomes first became statistically significant at age three.114 The experimental group also scored as high as a normal birth weight comparison group. A recent review of interventions targeting socially deprived families concluded that home visits accompanied by early stimulation in the neonatal unit, as well as by preschool placement, appeared to improve the cognitive development of low birth weight and premature children.115
In sum, early intervention can improve the cognitive and behavioral development of low birth weight children. Two-generation programs, which serve both mothers and children, and those that combine home visits with either center-based day care or hospital-based therapy appear particularly effective, with more pronounced gains for heavier low birth weight children.