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Epidemiology Research Unit, Tropical Medicine Research Institute, University of the West Indies, Mona, Kingston, Jamaica and * Center for International Child Health, Institute of Child Health, London, UK
2To whom correspondence should be addressed. E-mail: susan.walker{at}uwimona.edu.jm.
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ABSTRACT |
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 TOP ABSTRACT SUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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KEY WORDS: • term low birth weight • development • psychosocial intervention • home environment
It is estimated from the WHO database on low birth weight that 11% of infants born in developing countries are term low-birth-weight (LBW),3 infants (birth weight < 2500 g) with intrauterine growth retardation (IUGR) (1). There is increasing evidence from industrialized countries that term LBW is associated with cognitive and behavioral deficits in children and adults (2–5).
There are few studies of the development of term LBW infants in developing countries in which LBW is usually associated with poverty and inadequate stimulation in the home as well as poor postnatal growth. These disadvantages may increase the children’s risk of poor development. In a Guatemalan study, term infants with IUGR had poorer cognitive development at 3 and 4 y of age than infants who were not growth retarded (6,7); in Brazil, term LBW infants had significantly lower scores on the Bayley Scales at 6 and 12 mo of age than infants with birth weight > 3 kg (8). In the Brazilian study, stimulation in the home was related to development in the LBW infants only, suggesting that they may be more affected by their environment than normal-birth-weight (NBW) infants.
Interventions to enhance the quality of the home environments of LBW infants through better maternal-child interaction and psychosocial stimulation could be an important strategy to improve developmental outcomes in these children. A multicenter randomized trial of an early educational intervention in preterm LBW infants in the United States showed significant benefits to the children’s development up to school age (9–11). However, the intervention was costly and center-based and is unlikely to be feasible in most developing countries. In Jamaica, we showed significant long-term benefits to the development of undernourished children from a psychosocial intervention conducted by paraprofessional home visitors (12,13). The objectives of this study were therefore to conduct a randomized trial of a psychosocial intervention among term LBW infants to determine any benefits to stimulation in the home and the children’s development during the first 2 y of life and to compare the development of the LBW groups with a group of matched NBW infants.
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SUBJECTS AND METHODS |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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12,000 deliveries per year. One hundred forty term (gestational age 
37 completed weeks) LBW infants (birth weight < 2500 g) and 94 NBW infants (birth weight 2500–4000 g) who fulfilled the selection criteria were enrolled. Inclusion criteria were maternal education below 3 secondary level examination passes and residence within the Kingston Metropolitan Area. Infants were excluded if they were twins, had congenital abnormalities, were admitted to the hospital’s special care nursery for >48 h, or the mother had been tested and was HIV positive. The NBW infants were matched for gender to 2 of every 3 LBW infants. The next eligible NBW infants born after the LBW infants were enrolled. The LBW infants were randomly assigned to the control (n = 70) or intervention group (n = 70); 63 infants per group was sufficient to detect a difference of 0.5 SD with 80% power at the 0.05 level. Ethical approval for the study was given by the Ethics Committee of the University of the West Indies. The mothers gave signed informed consent to participate in the study. Intervention. All infants were visited weekly by community health workers to obtain information on infant feeding and morbidity. Infants and mothers in the intervention group participated in 2 intervention periods. Previously we had conducted several successful interventions in Jamaica beginning with children > 6 mo old (12,13); therefore, we used this intervention from 7 mo of age. However, this study was our first experience with newborns and we thought that mothers might be particularly receptive to intervention immediately after birth. For both phases, the community health workers received 2 wk of training in child development, the conduct of the intervention, and on the use of the curriculum manuals. During this period, they also assisted with the preparation of the toys used in the intervention. The first phase began with 1 contact in the hospital when the aims of the program were explained, followed by weekly 1-h home visits for 8 wk by 1 of 2 community health workers. The intervention focused on improving the mothers’ responsiveness to their infants. The mothers were encouraged to converse with and sing to their infants, respond to their cues, show affection, and focus their attention on the environment. The aims of the intervention were based on The Programme for the Enrichment of Interactions between Mothers and Children (14), and a few activities were taken from a curriculum developed at the University of Miami (15). The supervisor participated in the first visit and also met weekly with the health aides to review and plan the visits. The 8-wk intervention had a significant beneficial effect on the children’s performance at age 7 mo on 1 of 2 tests of intentional problem solving ability and on their behavior during the test session (16).
The second phase of intervention began after a 5-mo interval and was conducted from 7 to 24 mo of age. The intervention comprised weekly home visits lasting 30 min and was similar to interventions we used previously (17,18). Three community health workers conducted the intervention, 2 of whom had been responsible for the earlier intervention. We focused on helping the mothers become more effective teachers of their children and enhancing maternal-child interactions. During the visit, the community health worker demonstrated play techniques to the mother and involved her in a play session with the child. The mothers were encouraged to use praise and positive reinforcement and discouraged from using physical punishment. Toys made from commonly available recyclable materials were left in the home each week, and mothers were encouraged to continue to play with their children in between the visits and to include activities in their daily routines. The community health workers met with the supervisor weekly to review the visits and the children’s progress to ensure that the activities were at the appropriate level; the supervisor accompanied the workers on visits monthly. Some visits were missed, usually because the mother was unavailable or it was not safe for the health aide to visit due to disturbances in the community. The median level of scheduled visits received by participants was 75% (3 visits per month, interquartile range 62.5–87.5%).
Anthropometry and gestational age.
The infants’ weight, length, and head circumference were measured according to standard procedures (19), and gestational age was determined by clinical examination (20) by 1 of 2 observers within 48 h of birth. Anthropometry was repeated every 3 mo for 2 y. Interobserver reliability was high for gestational age and all anthropometric measurements (intraclass correlation coefficients 0.97, n = 20).
Maternal characteristics and socioeconomic status. A questionnaire was administered to the mothers on enrollment to obtain information on maternal characteristics. Their homes were visited 1 wk later to assess socioeconomic status (housing quality and possessions). The mother’s vocabulary was measured with the Peabody Picture Vocabulary Test (PPVT) (21).
Stimulation in the home. The level of stimulation in the home was assessed when the children were 12 mo old using the Caldwell HOME inventory (HOME) (22), which was previously modified to be appropriate for use in Jamaica. Modifications comprised rewording to improve comprehension, reducing a few cutoff values to ensure more variation (e.g., the number of books in the home was reduced), and combining some questions to reduce those with extremely few positive responses. The inventory is related to children’s development in Jamaica (23,24) and has the following subscales: maternal involvement, avoidance of restriction and punishment, emotional and verbal responsivity, play materials, and organization of the environment. A single researcher conducted the observations and obtained >90% agreement (n = 20) with the trainer before beginning the study. She was unaware of the children’s anthropometry and developmental progress; however, because we left toys in the homes and mothers sometimes commented on the intervention, she may have realized the group assignment in some cases.
Developmental levels. We previously reported the children’s cognitive ability at 7 mo on 2 intentional problem solving tests (16). One test comprised finding a toy hidden under a cover (cover test), and the other test involved retrieving a toy by pulling on a cloth (support test). The LBW intervention group had higher scores on the cover test than the LBW control group. The NBW group had higher scores than the LBW control group on both tests and higher scores than the LBW intervention group on the support test.
The children’s developmental levels were assessed at 15 and 24 mo of age with the Griffiths Mental Developmental Scales (25). These have been used in several studies in Jamaica and are predictive of scores at ages 8–15 y on the Stanford Binet and Wechsler Intelligence Scales for Children-Revised (12). All tests were conducted at our research unit. A single tester conducted all tests at 15 mo and 82% of tests at 24 mo. The remaining tests were conducted by one other tester. Interobserver agreement (intraclass correlation coefficient) for the global developmental quotient (DQ) between the testers and the trainer was >0.98 and interobserver agreement between the 2 testers was 0.99 (n = 16). The testers did not know the children’s group assignment and tested equal proportions of children from each group at 24 mo. The testers’ scores were compared at the end of the study; for the locomotor subscale, the difference between the testers approached significance (P = 0.064). We therefore adjusted for tester in the analyses (see below).
Statistical analysis.
A housing score was calculated from factor analysis of crowding in the home (persons/room), ratings of water supply (0 = >100 yards away to 6 = nonshared inside pipe) and toilet facilities (0 = none to 6 nonshared inside flush toilet) and number of possessions (range 0–10). This score was used in the analyses as a measure of socioeconomic status. We used similar scores previously, which were associated with postnatal nutritional status (13,26). The housing score was moderately correlated with maternal education (r = 0.14, P < 0.05). The children’s height-for-age and weight-for-height Z-scores were calculated using Epinut (Epinfo Version 6, Centers for Disease Control). Differences among the groups in social background variables and anthropometry were examined by ANOVA or 
2 analysis. The effect of the intervention on the HOME scores and developmental levels was examined by t test comparing the LBW intervention and LBW control groups. Multiple regression analyses were used to determine differences between the LBW and NBW infants in development, adjusting for possible covariates. Dummy codes were used for each of the LBW groups with the NBW group as the reference. Variables that were significantly associated with at least 1 of the subscales or DQ in univariate analyses were offered stepwise before entering the dummy variables for group. At 15 mo, the covariates offered were birth order (1 = 1, >1 = 0), gestational age, mothers’ PPVT, marital status (married or cohabiting = 1, single = 0), and housing score. Gestational age was not linearly related to development but DQs were lower in children born between 37 and 37.9 wk compared with those born at or after 38 wk. Gestational age was therefore used as a dichotomous variable (<38 wk = 0, 38 wk = 1). At age 24 mo, the covariates offered were gestational age, mothers’ PPVT, mothers’ age on enrollment (<18 y = 1 18 y = 0), and tester. Analyses were conducted with the Statistical Package for the Social Sciences (SPSS). Differences were considered significant at P < 0.05.
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RESULTS |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Developmental levels. Differences between the LBW intervention and control groups for the children’s DQ and subscale scores were determined initially by t test (Table 2). The intervention group had higher DQs (P < 0.05) and higher scores on the performance subscale (P < 0.02) than the control group at 15 mo and higher scores on the hand and eye (P < 0.05) and performance subscales (P < 0.02) at 24 mo.
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The effect of the intervention on DQ at 15 mo, the performance subscale at 15 and 24 mo, and the hand and eye subscale at 24 mo after adjusting for possible covariates was determined by multiple regression analyses (Table 3). Covariates were offered stepwise and then group (intervention = 1, control = 0) was entered. The intervened group had significantly higher DQs and higher scores on the performance subscale, but the difference in the hand and eye subscale was no longer significant.
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The intervention in early infancy had significant benefits to the children’s cognition at age 7 mo. To determine whether the intervention after 7 mo contributed to the children’s developmental levels, we repeated the regressions entering the children’s cognitive scores at 7 mo before group. The intervention effect on DQ and hand and eye was no longer significant; however, significant benefits remained for the performance subscale at 15 and 24 mo (Table 3). We calculated SD scores to compare the difference between the intervention and control groups at 7 mo with the later Griffiths test scores. The differences between the groups were not significantly greater at the later time points, although the difference for the performance subscales was slightly greater than for the 7-mo cognitive score (Table 4).
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DISCUSSION |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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The benefits were smaller than those found in previous Jamaican studies with undernourished children that used an intervention curriculum similar to the one used in this study from 7 to 24 mo (12,23). Possible explanations for the smaller benefits are that in the present study, the length of the visits was reduced from 1 h to 30 min, which may be less effective. Alternately, the characteristics of the children may have been important. They differed from the previous studies in that they were younger, born LBW at term, but were growing reasonably well.
We are not aware of any other study of a psychosocial intervention with term LBW infants; however, several such studies have been conducted in the United States with preterm LBW infants. Some interventions were targeted to high risk groups such as teenage mothers or low-income women (28,29), whereas others included more heterogeneous samples (30–32). The interventions varied in the frequency of home visits and duration of the interventions and in the case of the Infant Health and Development Program, also included center-based education for the children (30). The findings have generally been consistent and have shown benefits to the children’s developmental levels in the range of 6–10 points. These benefits were greater than those in our study, which may be due in part to the characteristics of the infants; compared with NBW infants, their delays in development were also greater than those of the term LBW infants in the present study. In some studies, benefits were not seen until age 2 (30) or 3 y (32); however, benefits were shown in y 1 of life in other studies (28,29,31).
Five months after the second phase of the intervention began, the intervention group had higher scores on the total HOME score and the maternal involvement and avoidance of restriction and punishment subscales. This finding was encouraging because we particularly focused on improving maternal child interaction including avoidance of punishment in the intervention. Improvements to the home environment were reported from home visiting interventions with preterm LBW infants (28,29,31); a meta-analysis of 12 home visiting studies in industrialized countries with a variety of high risk groups also found benefits to the HOME (33). The benefits to the home environment can be viewed as an intermediate outcome through which interventions affect development. In the Infant Health and Development Program, improvements to the home environment partially or wholly mediated benefits to some of the cognitive and behavioral outcomes (34). We also found that the total HOME score appeared to mediate some of the benefits of the intervention. If the mothers’ behavior is changed, the benefits are more likely to be sustainable or even increase and could spread to younger siblings (35). Follow-up of the children in this study is warranted to determine whether benefits to the home environment were sustained and contribute to continued differences in development between the intervention and control groups.
The intervention was conducted in 2 phases, one for 8 wk from birth and the second from 7 to 24 mo of age. The early intervention had significant benefits to the children’s intentional problem-solving ability at age 7 mo (16). When we controlled for the children’s scores on that test, the benefits to the DQ and hand and eye subscale were not significant; however, the benefits to the performance subscale remained. This suggests that the benefits of the intervention were due in part to the early intervention and that most of the effect of the later intervention was restricted to the performance subscale. The differences between the groups in SD scores at 7, 15, and 24 mo also suggest this because the differences were similar except for slightly greater differences in the performance subscales.
The strengths of the study were that children were randomized to treatment group, and there was little loss from the sample. Furthermore, we collected information on social and maternal characteristics and controlled for covariates in the analyses. However, because of the nature of the intervention, it was not possible to have a placebo, although both groups received weekly visits to obtain information on morbidity and infant feeding. The persons who conducted the developmental tests were unaware of the children’s group assignment. The observer who conducted the HOME inventory may have become aware of the children’s group assignment if intervention toys were visible in the home or through the mothers remarks. It is unknown whether this affected the results. A further limitation to the study was that we did not have groups assigned to only one or the other of the 2 interventions and are therefore unable to determine whether the benefits of the early intervention would have been sustained without participation in the later intervention or what the effects of the later intervention would have been without the earlier one.
This study was designed to determine the efficacy of the intervention and, as such, we hired community health workers who were supervised by members of the research team. In another study conducted at about the same time, which targeted undernourished children, we showed that the later intervention can be incorporated into the usual duties of community health workers in government clinics (36). The cost of the program includes supplies, training of health staff and a coordinator, and will vary by country depending on the cost and workload of staff.
The developmental levels of the LBW nonintervention infants were significantly lower than those of the NBW infants at both 15 and 24 mo of age. We had extensive social background data and there were few significant differences between the LBW and NBW groups. Differences in social background are usually reported between LBW and NBW infants (37). However, in this study we enrolled all subjects from a hospital that serves predominantly women from poor neighborhoods in Kingston and further restricted the range in social background by recruiting only women with <3 secondary examination passes. It was our objective to recruit NBW infants from as similar social backgrounds to the LBW infants as possible, so that we could focus on differences that were associated with birth weight status. We controlled for possible social background cofounders in the analyses and excluded infants with health complications in the immediate postnatal period. It is therefore likely that the developmental delays in the LBW infants are associated with intrauterine growth retardation. The magnitude of the difference between the LBW and NBW infants was 0.4 SD; the importance of such differences in developmental levels is controversial (38). The size of the delays may change as the children develop as has been found elsewhere (2,39).
Our results show that term LBW infants have developmental delays in the first 2 y of life compared with NBW infants from similar poor social backgrounds. A psychosocial intervention was beneficial to the development of term LBW children; however, these benefits were smaller than those seen in interventions with undernourished or preterm children in whom the developmental delays are also greater. It is possible that greater benefits will be seen at later ages as has been reported elsewhere (40).
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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3 Abbreviations used: DQ, developmental quotient; HOME, Caldwell HOME inventory; IUGR, intrauterine growth retardation; LBW, low birth weight; NBW, normal birth weight; PPVT, Peabody Picture Vocabulary Test.
Manuscript received 6 November 2003. Initial review completed 9 December 2003. Revision accepted 11 March 2004.
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LITERATURE CITED |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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1. de Onis, M., Blossner, M. & Villar, J. (1998) Levels and patterns of intrauterine growth retardation in developing countries. Eur. J. Clin. Nutr. 52(suppl. 1):S5-S15.
2. Grantham-McGregor, S. M. (1998) Small for gestational age, term babies, in the first six years of life. Eur. J. Clin. Nutr. 52(suppl. 1):S59-S64.
3. Goldenberg, R. L., DuBard, M. B., Cliver, S. P., Nelson, K. G., Blankson, K., Ramey, S. L. & Herman, A. (1996) Pregnancy outcome and intelligence at age five. Am. J. Obstet. Gynecol. 175:1511-1515.[Medline]
4. Sommerfelt, K., Andersson, H. W., Sonnander, K., Ahlsten, G., Ellersten, B., Markestad, T., Jacobsen, G., Hoffman, H. J. & Bakketeig, L. (2000) Cognitive development of term small for gestational age children at five years of age. Arch. Dis. Child. 83:25-30.
5. Strauss, R. S. & Dietz, W. H. (1998) Growth and development of term children born with low birth weight: effects of genetic and environmental factors. J. Pediatr. 133:67-72.[Medline]
6. Villar, J., Smeriglio, V., Martorell, R., Brown, C. H. & Klein, R. E. (1984) Heterogeneous growth and mental development of intrauterine growth-retarded infants during the first 3years of life. Pediatrics 74:783-791.
7. Gorman, K. S. & Pollitt, E. (1992) Relationship between weight and body proportionality at birth, growth during the first year of life, and cognitive development at 36, 48, and 60 months. Infant Behav. Dev. 15:279-296.
8. Grantham-McGregor, S. M., Lira, P. I., Ashworth, A., Morris, S. S. & Assuncao, A.M.S. (1998) The development of low birthweight term infants and the effects of the environment in north-east Brazil. J. Pediatr. 132:661-666.[Medline]
9. McCormick, M. C., McCarton, C., Brooks-Gunn, J., Belt, P. & Gross, R. T. (1998) The Infant Health and Development Program: interim summary. J. Dev. Behav. Pediatr. 19:359-370.[Medline]
10. Holloman, H. A. & Scott, K. G. (1998) Influence of birth weight on educational outcomes at age 9: the Miami site of the Infant Health and Development Program. J. Dev. Behav. Pediatr. 19:404-410.[Medline]
11. Hill, J. L., Brooks-Gunn, J. & Waldfogel, J. (2003) Sustained effects of high participation in an early intervention for low-birth-weight premature infants. Dev. Psychol. 39:730-744.[Medline]
12. Grantham-McGregor, S., Powell, C., Walker, S., Chang, S. & Fletcher, P. (1994) The long-term follow-up of severely malnourished children who participated in an intervention program. Child Dev. 65:428-439.[Medline]
13. Walker, S. P., Grantham-McGregor, S. M., Powell, C. A. & Chang, S. M. (2000) Effects of growth restriction in early childhood on growth, IQ and cognition at age 11 to 12 years and the benefits of nutritional supplementation and psychosocial stimulation. J. Pediatr. 137:36-41.[Medline]
14. World Health Organization/Division of Mental Health (1995) Improving the Psychosocial Development of Children: A Programme for the Enrichment of Interactions Between Mothers and Children (MNH/PSF/93.6) 1995 WHO Geneva, Switzerland.
15. Scott, M. S. & Scott, K. G. (1992) The Outcome Curriculum 1992 Department of Psychology, University of Miami Coral Gables, FL.
16. Meeks Gardner, J., Walker, S. P., Powell, C. A. & Grantham-McGregor, S. (2003) A randomized controlled trial of a home-visiting intervention on cognition and behavior in term low birth weight infants. J. Pediatr. 143:634-639.[Medline]
17. Powell, C. & Grantham-McGregor, S. M. (1989) Home visiting of varying frequency and child development. Pediatrics 84:157-164.
18. McDonald, K., Grantham-McGregor, S. M. & Chang, S. (1989) Social stimulation of the severely malnourished child: a home training program. Indian J. Pediatr. 56:97-103.[Medline]
19. Lohman, T. G., Roche, A. F. & Martorell, R. (1988) Anthropometric Standardization Reference Manual 1988 Human Kinetics Books Champaign, IL.
20. Dubowitz, L.M.S. & Dubowitz, V. (1977) Gestational Age of the Newborn 1977 Addison-Wesley Publishing Company Boston, MA.
21. Dunn, L & Dunn, L. (1981) Peabody Picture Vocabulary Test, rev. ed. 1981 American Guidance Services Circle Pines, MN.
22. Caldwell, B. M. (1967) Descriptive evaluation of child development and of developmental settings. Pediatrics 40:46-50.
23. Grantham-McGregor, S., Powell, C., Walker, S. & Himes, J. (1991) Nutritional supplementation, psychosocial stimulation and mental development of stunted children: the Jamaican Study. Lancet 338:1-5.[Medline]
24. Meeks Gardner, J. M., Walker, S. P., Chang, S. M., Vutchkov, M. & Lalor, G. C. (1998) Undernutrition and elevated blood lead levels: effects on psychomotor development among Jamaican children. Public Health Nutr. 1:177-179.[Medline]
25. Griffiths, R. (1967) The Abilities of Babies 1967 Association for Research in Infant and Child Development High Wycombe, UK.
26. Walker, S. P., Powell, C. A., Grantham-McGregor, S. M., Himes, J. & Chang, S. M. (1991) Nutritional supplementation, and growth of stunted children: the Jamaican study. Am. J. Clin. Nutr. 54:642-648.
27. Freedman, L. S. & Schatzkin, A. (1992) Sample size for studying intermediate endpoints within intervention trials of observational studies. Am. J. Epidem. 136:1148-1159.
28. Ross, G. S. (1984) Home intervention for premature infants of low-income families. Am. J. Orthopsychiatry 54:263-270.[Medline]
29. Field, T. M., Widmayer, S. M., Stringer, S. & Ignatoff, E. (1980) Teenage, lower class, black mothers and their preterm infants: an intervention and developmental follow-up. Child Dev. 51:426-436.[Medline]
30. Brooks-Gunn, J., Klebanov, P. K., Liaw, F. & Spiker, D. (1993) Enhancing the development of low-birthweight, premature infants: changes in cognition and behavior over the first three years. Child Dev. 64:736-753.[Medline]
31. Barrera, M. E., Rosenbaum, P. L. & Cunningham, C. E. (1986) Early home intervention with low-birth-weight infants and their parents. Child Dev. 57:20-33.[Medline]
32. Rauh, V. A., Achenbach, T. M., Nucombe, B., Howell, C. T. & Teti, D. M. (1988) Minimizing adverse effects of low birthweight: four-year results of an early intervention. Child Dev. 59:544-553.[Medline]
33. Kendrick, D., Elkan, R., Hewitt, M., Dewey, M., Blair, M., Robinson, J., Williams, D. & Brummell, K. (2000) Does home visiting improve parenting and quality of the home environment? A systematic review and meta analysis. Arch. Dis. Child. 82:443-451.
34. Bradley, R. H., Whiteside, L., Mundfrom, D. J., Casey, P. H., Caldwell, B. M. & Barret, K. (1994) Impact of Infant Health and Development Program (IDHP) on the home environments of infants born prematurely and with low birth weight. J. Educ. Psychol. 86:531-541.
35. Seitz, V. & Apfel, N. H. (1994) Parent-focused intervention: diffusion effects on siblings. Child Dev. 65:677-683.[Medline]
36. Powell, C., Baker-Henningham, H., Walker, S., Gernay, J. & Grantham-McGregor, S. () Integrating early stimulation into primary health care services for undernourished Jamaican children: a randomized controlled trial. Br. Med. J. (in press).
37. Kramer, M. S. (1998) Socioeconomic determinants of intrauterine growth retardation. Eur. J. Clin. Nutr. 52:S29-S53.
38. Pollitt, E. (2001) Statistical and psychobiological significance in developmental research. Am. J. Clin. Nutr. 74:281-282.
39. Frisk, V., Amsel, R. & Whyte, H.E.A. (2002) The importance of head growth patterns in predicting the cognitive abilities and literacy skills of small-for-gestational-age children. Dev. Neuropsychol. 22:565-593.[Medline]
40. Achenbach, T. M., Howell, C. T., Aoki, M. F. & Rauh, V. A. (1993) Nine-year outcome of the Vermont Intervention Program for low birth weight infants. Pediatrics 91:45-55.
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