Showing papers by "Alan Leviton published in 1991"

Low-level lead exposure and children's cognitive function in the preschool years.

Abstract: In a cohort of 170 middle and upper-middle class children participating in a prospective study of child development and low-level lead exposure, higher blood lead levels at age 24 months were associated with lower scores at age 57 months on the McCarthy Scales of Children's Abilities. The mean blood lead level at age 24 months was 6.8 micrograms/dL (SD = 6.3; 75th, 90th, and 99th percentiles: 8.8, 13.7, 23.6, respectively) and for all but 1 child was less than 25 micrograms/dL, the current definition of an "elevated" level. After adjustment for confounding, scores on the General Cognitive Index decreased approximately 3 points (SE = 1.4) for each natural log unit increase in 24-month blood lead level. The inverse association between lead level and performance was especially prominent for visual-spatial and visual-motor integration skills. Higher prenatal exposures were not associated with lower scores at 57 months except in the subgroup of children with "high" concurrent blood lead levels (ie, greater than or equal to 10 micrograms/dL). The concentration of lead in the dentine of shed deciduous teeth was not significantly associated with children's performance after adjustment for confounding.

How much of neonatal encephalopathy is due to birth asphyxia

Abstract: In the literature on neonatal encephalopathy, the pervasive assumption is that once infants with major malformations or infections have been excluded, most of the remaining cases are due to birth asphyxia. Assessing the proportion of neonatal encephalopathy that is due to asphyxia during birth is difficult because of problems in defining asphyxia and neonatal encephalopathy and in recognizing the cause of neonatal neurologic illness. Available evidence indicates that neonatal neurologic signs are not strongly related to obstetric complications, signs of fetal distress, or biochemical markers usually considered to indicate perinatal asphyxia. Most studies that have sought positive evidence of independent markers of intrapartum asphyxia have found them to be absent in a large majority of neurologically symptomatic neonates. We conclude that the proportion of neonatal encephalopathy that is asphyxial in origin is not known but warrants examination, especially in view of the probable need in the near future to identify, on the basis of evidence available in the first hour or so of life, suitable candidates for clinical trials of powerful but risky treatments of birth asphyxia.

Labor and Deliver Characteristics and the Risk of Germinal Matrix Hemorrhage in Low Birth Weight Infants

Abstract: To assess the influence of labor and delivery events on the risk of germinal matrix hemorrhage in preterm newborns, we conducted a review of data collected on 449 babies who weighed 1.5 kg or less. Babies delivered vaginally were more likely to have germinal matrix hemorrhage than were babies delivered abdominally (odds ratio, 2.5; 95% confidence interval, 1.4,3.3). Among babies delivered vaginally, the risk of germinal matrix hemorrhage was increased by 39% if labor lasted more than 12 hours. Among babies delivered abdominally, the occurrence of any labor was accompanied by a 150% increased risk of germinal matrix hemorrhage. The only indication for abdominal delivery associated with an increased risk of germinal matrix hemorrhage was impending amnionitis (odds ratio, 2.6; 95% confidence interval, 1.2,5.7), whereas the only indication associated with a decreased risk was preeclampsia (odds ratio, 0.2; 95% confidence interval, 0.6). Epidural and local anesthesia were associated with a reduced risk of germinal matrix hemorrhage among babies delivered abdominally. We conclude that delivery practices, or their indications, appear to influence the risk of germinal matrix hemorrhage in low birth weight babies.

Lead levels among various deciduous tooth types.

Abstract: The amount of lead in deciduous teeth has been used extensively as a marker for infant lead exposure and body burden. However, the pattern of lead abundances among the various tooth positions in a child's mouth appears to be non-uniform. Taken together these findings show an apparently inconsistent pattern among the tooth types. These comparisons are complicated by different research groups using different portions of the tooth. This issue is of significance to those who wish to compare the lead burden of children but have available teeth from different positions from the various children. By examining a large number of teeth from two different populations, the authors hope to explore the more universal aspects of any variability among tooth types.

Macroscopic enamel defects of primary anterior teeth--types, prevalence, and distribution.

Abstract: A total of 40.7% of 509 exfoliated primary anterior teeth from children who were healthy products of uneventful pregnancies exhibited at least one macroscopic enamel defect. Twenty percent of the teeth exhibited hypoplastic defects (HD), 12.4% exhibited white-cream opacities (WCO), and 9.8% exhibited yellow-brown opacities (YBO). Slightly more than a third (33.6%) of the teeth had defects we considered to be developmental enamel defects (DED). The occurrence of DED did not vary with gender, side of mouth, individual tooth types, or racial background. DED occurred with increased frequency on maxillary teeth, facial surfaces, and the middle third of affected surfaces. These locations have thicker enamel than other sites and may be more susceptible to insult if vulnerability is a function of metabolic demand of the rapidly secreting ameloblasts. Twenty-five per cent of the maxillary incisors and 10.1% of the mandibular incisors exhibited HD whose locations coincided with enamel forming at birth. A third (33.3%) of the canines exhibited HD, which occurred most commonly in the middle third of the facial surfaces. These defects are believed to occur approximately six months postnatally and may be primarily due to mechanical trauma. YBO most commonly occurred on the middle third of the facial surfaces, while WCO on the gingival third. Neither YBO nor WCO followed a chronologic pattern.