Marie C. McCormick

The Contribution of Low Birth Weight to Infant Mortality and Childhood Morbidity

The low-birth-weight infant remains at much higher risk of mortality than the infant with normal weight at birth. In the neonatal period, when most infant deaths occur, the proportion of low-birth-weight infants, especially those with very low weight, is the major determinant of the magnitude of the mortality rates. Furthermore, differences in low-birth-weight rates account for the higher neonatal mortality rates observed in some groups, particularly those characterized by socioeconomic disadvantages. Much of the recent decline in neonatal mortality can be attributed to increased survival among low-birth-weight infants, apparently as a result of hospital-based services. The application of these services is currently considered cost-effective, although whether this will continue to be true in the future is unclear because of the increased survival of very tiny infants. Although low-birth-weight infants remain at increased risk of both postneonatal mortality and morbidity in infancy and early childhood, the risk is substantially smaller than that of neonatal death. In addition, these adverse later outcomes have not offset the gains achieved in the neonatal period. Nonetheless, the increased survival of high-risk infants raises concern about their future requirements for special medical and educational services and about the stress on their families. Despite increased access to antenatal services, only moderate declines in the proportion of low-birth-weight infants has been observed, and almost no change has occurred in the proportion of those with very low weight at birth. In addition, in many areas of the country the birth-weight-specific neonatal mortality rates are similar for groups at high and low risk of neonatal death. In view of these findings, continuation of the current decline in neonatal mortality and reduction of the mortality differentials between high- and low-risk groups require the identification and more effective implementation of strategies for the prevention of low-weight births.

Increased Risk of Adverse Neurological Development for Late Preterm Infants

OBJECTIVE To assess the risks of moderate prematurity for cerebral palsy (CP), developmental delay/mental retardation (DD/MR), and seizure disorders in early childhood. STUDY DESIGN Retrospective cohort study using hospitalization and outpatient databases from the Northern California Kaiser Permanente Medical Care Program. Data covered 141 321 children > or =30 weeks born between Jan 1, 2000, and June 30, 2004, with follow-up through June 30, 2005. Presence of CP, DD/MR, and seizures was based on International Classification of Diseases, Ninth Revision codes identified in the encounter data. Separate Cox proportional hazard models were used for each of the outcomes, with crude and adjusted hazard ratios calculated for each gestational age group. RESULTS Decreasing gestational age was associated with increased incidence of CP and DD/MR, even for those born at 34 to 36 weeks gestation. Children born late preterm were >3 times as likely (hazard ratio, 3.39; 95% CI, 2.54-4.52) as children born at term to be diagnosed with CP. A modest association with DD/MR was found for children born at 34 to 36 weeks (hazard ratio, 1.25; 95% CI, 1.01-1.54), but not for children in whom seizures were diagnosed. CONCLUSIONS Prematurity is associated with long-term neurodevelopmental consequences, with risks increasing as gestation decreases, even in infants born at 34 to 36 weeks.

Early Intervention in Low Birth Weight Premature Infants: Results at 18 Years of Age for the Infant Health and Development Program

OBJECTIVE. To assess whether improvements in cognitive and behavioral development seen in preschool educational programs persist, we compared those in a multisite randomized trial of such a program over the first 3 years of life (INT) to those with follow-up only (FUO) at 18 months of age. METHODS. This was a prospective follow-up of the Infant Health and Development Program at 8 sites heterogeneous for sociodemographic characteristics. Originally 985 children were randomized to the INT (n = 377) or FUO (n = 608) groups within 2 birth weight strata: heavier low birth weight (HLBW; 2001–2499 g) and lighter low birth weight (LLBW; ≤2000 g). Primary outcome measures were the Peabody Picture Vocabulary Test (PPVT-III), reading and mathematics subscales of the Woodcock-Johnson Tests of Achievement, youth self-report on the Total Behavior Problem Index, and high-risk behaviors on the Youth Risk Behavior Surveillance System (YRBSS). Secondary outcomes included Weschler full-scale IQ, caregiver report on the Total Behavior Problem Index, and caregiver and youth self-reported physical health using the Medical Outcome Study measure. Assessors were masked as to study status. RESULTS. We assessed 636 youths at 18 years (64.6% of the 985, 72% of whom had not died or refused at prior assessments). After adjusting for cohort attrition, differences favoring the INT group were seen on the Woodcock-Johnson Tests of Achievement in math (5.1 points), YRBSS (−0.7 points), and the PPVT-III (3.8 points) in the HLBW youth. In the LLBW youth, the Woodcock-Johnson Tests of Achievement in reading was higher in the FUO than INT group (4.2). CONCLUSIONS. The findings in the HLBW INT group provide support for preschool education to make long-term changes in a diverse group of children who are at developmental risk. The lack of observable benefit in the LLBW group raises questions about the biological and educational factors that foster or inhibit sustained effects of early educational intervention.

Very low birth weight children: Behavior problems and school difficulty in a national sample*

We addressed three questions concerning the behavioral and academic status of low and very low birth weight infants through a secondary analysis of the 1981 National Health Interview Survey--Child Health Supplement: (1) in children born with very low birth weight, what is the risk of behavior problems and school difficulty compared with that in heavier low birth weight and normal birth weight children? (2) What are the correlates of school difficulty? (3) Are behavior problems associated with school difficulty when variables are controlled for these correlates? The analysis revealed that 34% of very low birth weight children could be characterized as having school difficulty, compared with 20% and 14% of the other groups, respectively, and that they were more likely to have higher scores on the hyperactive subscale of the Behavior Problems Index. Although a broad array of sociodemographic factors correlated with school difficulty, very low birth weight and hyperactivity scores contributed independently to the risk of academic problems. We conclude that very low birth weight infants are at risk of having school problems that are in part associated with hyperactive behavior.

Factors associated with smoking in low-income pregnant women: relationship to birth weight, stressful life events, social support, health behaviors and mental distress

Since low-income women are at increased risk of having low birth weight infants, factors associated with birth weight among such groups have special relevance. Cigarette-smoking has emerged as an important predictor of low birth weight due to intrauterine growth retardation and pre-term delivery. After confirming the relation of smoking with birth weight, we examined the association of smoking with sociodemographic factors, attitudes towards pregnancy, health behaviors, stressful life events, social support, and symptoms of mental distress in a cohort of 458 Central Harlem women. We found that social support, stress and mental health were associated with smoking behavior but not directly with birth weight. These findings suggest that programs designed to modify health behaviors such as smoking during pregnancy must also take into account such characteristics of the women and their environments which may make behavioral change difficult. Moreover, programs aimed at fostering better health behaviors to improve pregnancy outcome may have to extend beyond the current pregnancy, as indicated by an association between prior adverse pregnancy outcome and smoking in the current pregnancy.

Declining severity adjusted mortality: evidence of improving neonatal intensive care.

Objectives. Declines in neonatal mortality have been attributed to neonatal intensive care. An alternative to the “better care” hypothesis is the “better babies” hypothesis; ie, very low birth weight infants are delivered less ill and therefore have better survival. Design. We ascertained outcomes of all live births <1500 g in two prospective inception cohorts. We estimated mortality risk from birth weight and illness severity on admission and measured therapeutic intensity. We calculated logistic regression models to estimate the changing odds of mortality between cohorts. Patients and Setting. Two cohorts in the same two hospitals, 5 years apart (1989–1990 and 1994–1995) (totaln = 739). Results. Neonatal intensive care unit mortality declined from 17.1% to 9.5%, and total mortality declined from 31.6% to 18.4%. Cohort 2 had lower risk (higher birth weight, gestational age, and Apgar scores and lower admission illness severity for newborns ≥750 g). Risk-adjusted mortality declined (odds ratio, 0.52; confidence interval, 0.29–0.96). One third of the decline was attributable to “better babies” and two thirds to “better care.” Use of surfactant, mechanical ventilation, and pressors became more aggressive, but decreases in monitoring, procedures, and transfusions resulted in little change in therapeutic intensity. Conclusions. Mortality decreased nearly 50% for infants <1500 g in 5 years. One third of this decline is attributable to improved condition on admission that reflects improving obstetric and delivery room care. Two thirds of the decline is attributable to more effective newborn intensive care, which was associated with greater aggressiveness of respiratory and cardiovascular treatments. Attribution of improved birth weight specific mortality solely to neonatal intensive care may underestimate the contribution of high-risk obstetric care in providing “better babies.”

School achievement and failure in very low birth weight children

The extent to which low birth weight confers a risk for poor school function remains an important question. Children (N = 1868) in four birth weight categories [extremely low birth weight (ELBW; children weighed ≤ 1000 g at birth, n = 247), other very low birth weight (1001 through 1500 g, n = 364), heavier low birth weight (1501 through 2500 g, n = 724), and normal birth weight (NBW > 2500 g, n = 533)] were compared on indicators of school achievement which included grade failure, placement in special classes, classification as handicapped, and math and reading achievement scores (Woodcock-Johnson Battery). Our results indicate that as birth weight decreases, the prevalence of grade failure, placement in special classes, and classification as handicapped increases, even when controlling for maternal education and neonatal stay. Moreover, ELBW children score lower than all other birth weight groups on math and reading achievement tests. Even among children with IQ scores above 85, ELBW children still obtain lower math scores than NBW children, suggesting the potential for future educational needs. J Dev Behav Pediatr 15:248–256, 1994. Index terms: at-risk infants, low birth weight infants, premature infants, school achievement, grade failure.

Prematurity: An Overview and Public Health Implications

The high rate of premature births in the United States remains a public health concern. These infants experience substantial morbidity and mortality in the newborn period, which translate into significant medical costs. In early childhood, survivors are characterized by a variety of health problems, including motor delay and/or cerebral palsy, lower IQs, behavior problems, and respiratory illness, especially asthma. Many experience difficulty with school work, lower health-related quality of life, and family stress. Emerging information in adolescence and young adulthood paints a more optimistic picture, with persistence of many problems but with better adaptation and more positive expectations by the young adults. Few opportunities for prevention have been identified; therefore, public health approaches to prematurity include assurance of delivery in a facility capable of managing neonatal complications, quality improvement to minimize interinstitutional variations, early developmental support for such infants, and attention to related family health issues.

Relevance of correlates of infant deaths for significant morbidity at 1 year of age

This paper examines the issue of whether or not factors identified as risks for death in the first year of life also serve as risks for morbidity in surviving infants through data collected on 390,425 live births, 5,084 infant deaths, and 4,327 surviving 1-year-old children among singleton births in eight geographically defined regions in the United States. Factors which presented risks for neonatal death, such as advanced maternal age and maternal history of prior fetal loss, proved to present risks for congenital anomalies/severe developmental delay, whereas factors heavily influenced by environmental conditions, such as young maternal age and lower maternal educational attainment, were associated with higher postneonatal mortality rates and other significant illness, among both low-birth-weight and normal-birth-weight infants. The association of delivery by cesarean section with death and morbidity was also explored.

Health care for children and youth in the United States: annual report on patterns of coverage, utilization, quality, and expenditures by income.

OBJECTIVES To examine differences by income in insurance coverage, health care utilization, expenditures, and quality of care for children in the United States. METHODS Two national health care databases serve as the sources of data for this report: the 2000-2002 Medical Expenditure Panel Survey (MEPS) and the 2001 Nationwide Inpatient Sample (NIS) from the Healthcare Cost and Utilization Project (HCUP). In the MEPS analyses, low income is defined as less than 200% of the federal poverty level and higher income is defined as 200% of the federal poverty level or more. For the HCUP analyses, median household income for the patients zip code of residence is used to assign community-level income to individual hospitalizations. RESULTS Coverage. Children from low-income families were more likely than children from middle-high-income families to be uninsured (13.0% vs 5.8%) or covered by public insurance (50.8% vs 7.3%), and less likely to be privately insured (36.2% vs 87.0%). Utilization. Children from low-income families were less likely to have had a medical office visit or a dental visit than children from middle-high-income families (63.7% vs 76.5% for office-based visits and 28.8% vs 51.4% for dental visits) and less likely to have medicines prescribed (45.1% vs 56.4%) or have utilized hospital outpatient services (5.2% vs 7.0%), but more likely to have made trips to the emergency department (14.6% vs 11.4%). Although low-income children comprise almost 40% of the child population, one quarter of total medical expenditures were for these children. Hospital Discharges. Significant differences by community-level income occurred in specific characteristics of hospitalizations, including admissions through the emergency department, expected payer, mean total charges per day, and reasons for hospital admission. Leading reasons for admission varied by income within and across age groups. Quality. Low-income children were more likely than middle-high-income children to have their parents report a big problem getting necessary care (2.4% vs 1.0%) and getting a referral to a specialist (11.5% vs 5.3%). Low-income children were at least twice as likely as middle-high-income children to have their parents report that health providers never/sometimes listened carefully to them (10.0% vs 5.1%), explained things clearly to the parents (9.6% vs 3.4%), and showed respect for what the parents had to say (9.2% vs 4.2%). Children from families with lower community-level incomes were more likely to experience ambulatory-sensitive hospitalizations. Racial/Ethnic Differences Between Income Groups. Use and expenditure patterns for most services were not significantly different between low- and middle-high-income black children and were lower than those for white children. CONCLUSIONS While health insurance coverage is still an important factor in obtaining health care, the data suggest that efforts beyond coverage may be needed to improve access and quality for low-income children overall and for children who are racial and ethnic minorities, regardless of income.