Steve Selvin

The Changing Prevalence of Autism in California

We conducted a population-based study of eight successive California births cohorts to examine the degree to which improvements in detection and changes in diagnosis contribute to the observed increase in autism prevalence. Children born in 1987-1994 who had autism were identified from the statewide agency responsible for coordinating services for individuals with developmental disabilities. To evaluate the role of diagnostic substitution, trends in prevalence of mental retardation without autism were also investigated. A total of 5038 children with full syndrome autism were identified from 4,590,333 California births, a prevalence of 11.0 per 10,000. During the study period, prevalence increased from 5.8 to 14.9 per 10,000, for an absolute change of 9.1 per 10,000. The pattern of increase was not influenced by maternal age, race/ethnicity, education, child gender, or plurality. During the same period, the prevalence of mental retardation without autism decreased from 28.8 to 19.5 per 10,000, for an absolute change of 9.3 per 10,000. These data suggest that improvements in detection and changes in diagnosis account for the observed increase in autism; whether there has also been a true increase in incidence is not known.

Increased mortality from lung cancer and bronchiectasis in young adults after exposure to arsenic in utero and in early childhood.

Arsenic in drinking water is an established cause of lung cancer, and preliminary evidence suggests that ingested arsenic may also cause nonmalignant lung disease. Antofagasta is the second largest city in Chile and had a distinct period of very high arsenic exposure that began in 1958 and lasted until 1971, when an arsenic removal plant was installed. This unique exposure scenario provides a rare opportunity to investigate the long-term mortality impact of early-life arsenic exposure. In this study, we compared mortality rates in Antofagasta in the period 1989–2000 with those of the rest of Chile, focusing on subjects who were born during or just before the peak exposure period and who were 30–49 years of age at the time of death. For the birth cohort born just before the high-exposure period (1950–1957) and exposed in early childhood, the standardized mortality ratio (SMR) for lung cancer was 7.0 [95% confidence interval (CI), 5.4–8.9; p < 0.001] and the SMR for bronchiectasis was 12.4 (95% CI, 3.3–31.7; p < 0.001). For those born during the high-exposure period (1958–1970) with probable exposure in utero and early childhood, the corresponding SMRs were 6.1 (95% CI, 3.5–9.9; p < 0.001) for lung cancer and 46.2 (95% CI, 21.1–87.7; p < 0.001) for bronchiectasis. These findings suggest that exposure to arsenic in drinking water during early childhood or in utero has pronounced pulmonary effects, greatly increasing subsequent mortality in young adults from both malignant and nonmalignant lung disease.

Descriptive Epidemiology of Autism in a California Population: Who Is at Risk?

We investigated the association between selected infant and maternal characteristics and autism risk. Children with autism born in California in 1989-1994 were identified through service agency records and compared with the total population of California live births for selected characteristics recorded on the birth certificate. Multivariate models were used to generate adjusted risk estimates. From a live birth population of more than 3.5 million, 4381 children with autism were identified. Increased risks were observed for males, multiple births, and children born to black mothers. Risk increased as maternal age and maternal education increased. Children born to immigrant mothers had similar or decreased risk compared with California-born mothers. Environmental factors associated with these demographic characteristics may interact with genetic vulnerability to increase the risk of autism.

Maternal weight gain pattern and birth weight

Objectives To determine the relationship between maternal weight gain pattern and birth weight. Methods All nonobese, white women delivered at the University of California, San Francisco, between 1980–1990 were eligible for this study. Our study group included 2994 uncomplicated pregnancies with complete data. All recorded prenatal weight gain measurements were used to estimate maternal trimester weight gain, pattern of gain (based on low versus not-low gain at each trimester), and total gain at delivery. Multiple linear regression analysis was used to assess the relationship between these weight gain measurements and fetal birth weight. Results After adjustment for seven covariates, each kilogram of maternal gain in the first, second, and third trimesters was associated with statistically significant increases in fetal birth weight of 18.0, 32.8, and 17.0 g, respectively. When compared with the pattern of gain that was not low in any trimester, patterns with low gain in the first and second trimesters or in the second and third trimesters were associated with significant decreases in birth weights of 133.0 and 88.5 g, but no important change in birth weight was seen for the group whose gains were low in the first and third trimesters. These findings were not due to differences in total weight gain, which averaged approximately 11 kg in these three pattern groups. Conclusion The results suggest that specific patterns of maternal weight gain, particularly weight gain during the second trimester, are related to fetal birth weight.

The pattern of maternal weight gain in women with good pregnancy outcomes.

OBJECTIVES This study describes the pattern of maternal weight gain in women with good pregnancy outcomes and provides data to fill in the provisional weight-gain charts published by the Institute of Medicine (IOM) in 1990. METHODS We selected 7002 women with good outcomes (defined by factors related to maternal and infant health) from the University of California, San Francisco, Perinatal Database. For each body mass index category, we compared percentiles of weight gain by trimester in women who achieved the IOM recommendations for total gain and those who did not. RESULTS Trimester rates of gain varied by body mass index category and exceeded IOM guidelines in all groups. Forty percent of these women with good outcomes had total gains within the guidelines and provided data to complete the IOM weight-gain charts. CONCLUSIONS Most women in this good-outcome sample would have been suspected of being at increased risk for poor outcome on the basis of their weight gain. This confirms the IOM recommendation that evaluation of the underlying causes of excessively high or low weight gain during pregnancy is necessary before appropriate interventions can be applied.

Factors associated with the pattern of maternal weight gain during pregnancy

Objective To examine the pattern of maternal weight gain using maternal characteristics and pregnancy outcome. Methods We used maternal weight data measured prospectively from all deliveries between 1980–1990 at the University of California, San Francisco. Piecewise linear regression was used to estimate the rate of maternal weight gain in each trimester. Bivariate techniques were used to examine associations between maternal weight gain per trimester and maternal characteristics and pregnancy outcomes. We also used multiple regression analysis to examine the relationship between maternal characteristics and trimester weight gain. Results Weight data for at least one trimester were available for 10,418 women. The average rate of weight gain (kg/week) was lowest during the first trimester (0.169 ± 0.268, n = 7587), peaked during the second trimester (0.563 ± 0.236, n = 8000), and slowed slightly in the third trimester (0.518 ± 0.234, n = 10,052). Maternal height, hypertension, cesarean delivery, and fetal size correlated positively with the rate of gain in each trimester, but pre-pregnancy body size, age, parity, smoking status, race-ethnicity, and diabetes were associated differently with gain, depending on which trimester was examined. The most important maternal predictors of weight gain per trimester were age and Asian race-ethnicity in the first trimester; pre-pregnancy body mass, parity, and height in the second; and hypertension, age, and parity in the third. Conclusion Maternal weight gain per trimester is associated with a number of maternal characteristics and pregnancy outcomes, and these relationships vary according to which trimester is being examined.

Socioeconomic status, neighborhood social conditions, and neural tube defects.

OBJECTIVES This study evaluated the contributions of lower socioeconomic status (SES) and neighborhood socioeconomic characteristics to neural tube defect etiology. The influence of additional factors, including periconceptional multivitamin use and race/ethnicity, was also explored. METHODS Data derived from a case-control study of California pregnancies from 1989 to 1991. Mothers of 538 (87.8% of eligible) case infants/fetuses with neural tube defects and mothers of 539 (88.2%) nonmalformed infants were interviewed about their SES. Reported addresses were linked to 1990 US census information to characterize neighborhoods. RESULTS Twofold elevated risks were observed for several SES indicators. Risks were somewhat confounded by vitamin use, race/ethnicity, age, body mass index, and fever but remained elevated after adjustment. A risk gradient was seen with increasing number of lower SES indicators. Women with 1 to 3 and 4 to 6 lower SES indicators had adjusted odds ratios of 1.6 (1.1-2.2) and 3.2 (1.9-5.4), respectively, compared with women with no lower SES indicators. CONCLUSIONS Both lower SES and residence in a SES-lower neighborhood increased the risk of an neural tube defect-affected pregnancy, with risks increasing across a gradient of SES indicators.

Neighborhood Socioeconomic Status, Maternal Race and Preterm Delivery: A Case-Control Study

PURPOSE To explore associations between neighborhood socioeconomic context and preterm delivery, independent of maternal and family socioeconomic status, in African-American and white women. METHODS A case-control study of African-American (n = 417) and white (n = 1244) women delivering infants at the University of California, San Franciscos Moffitt Hospital, between 1980 and 1990. RESULTS Neighborhood socioeconomic contexts were associated with preterm delivery but associations were non-linear and varied with race/ethnicity. For African-American women, living in a neighborhood with either high or low median household income was associated with an increased risk of spontaneous preterm delivery, as was living in a neighborhood with large increases or decreases in the proportion of African-American residents during the study decade. Residence in neighborhoods with high and low rates of male unemployment was associated with a decreased risk of preterm delivery. Among white women only large positive and negative changes in neighborhood male unemployment were associated with risk of preterm delivery. CONCLUSIONS Neighborhood factors and changes in neighborhoods over time are related to preterm delivery, although the mechanisms linking local environments to maternal risk remain to be specified.

Maternal residential proximity to hazardous waste sites and risk for selected congenital malformations.

Using data from two population‐based case‐control studies, we investigated whether maternal residential proximity to hazardous waste sites increased the risk for neural tube defects, conotruncal heart defects, and oral cleft defects in California. We obtained a residential history by interview for mothers of 507 neural tube defect cases (82.7% of eligible) and their 517 controls (84.6%); and 201 heart cases (84.4%), 439 cleft cases (82.2%), and their 455 controls (72.1%). We identified the locations of 764 inactive hazardous waste sites and systematically collected information on site‐related contamination for the subset of 105 National Priority List sites. After controlling for several potential confounders, we found little or no increased risk for maternal residence in a census tract containing a site [odds ratio (OR) = 0.9, 95% confidence interval (CI) = 0.7–1.3 for neural tube defects; OR = 1.3, 95% CI = 0.8–2.1 for heart cases; OR = 1.2, 95% CI = 0.8–1.8 for clefts], but elevated risks for neural tube defects (OR = 2.1, 95% CI = 0.6–7.6) and heart defects (OR = 4.2, 95% CI = 0.7–26.5) for maternal residence within 1/4 mile of a National Priority List site. Furthermore, we observed elevated ORs (≥2.0) for neural tube defects and heart defects in association with maternal residence within 1 mile of National Priority List sites containing selected chemical contaminants. Among controls, only 0.6% and 4.4% lived within 1/4 mile and 1 mile of a National Priority List site, respectively, resulting in imprecision in risk estimation.

Hypospadias in California: Trends and Descriptive Epidemiology

Background The occurrence of hypospadias has been reported to be increasing. The objectives of this study were to extend the literature on the descriptive epidemiology of hypospadias and to determine whether its birth prevalence increased in California in recent years. We used actively ascertained, population-based data for which detailed clinical descriptions permitted careful phenotypic classifications. Methods We examined registry data on 5838 male live births and stillbirths that occurred in California from 1984 through 1997. To reduce pathogenic heterogeneity, cases were classified as mild, severe, or not otherwise specified based on the anatomic position of the urethral opening. We also classified cases as isolated or nonisolated based on the presence and type of accompanying malformations. We used multivariable Poisson regression analysis to examine time trends and risk factors. Results There was no evidence for an increase in prevalence of any of the case groups between 1989 and 1997. The adjusted relative risk (RR) for change in prevalence per year of isolated severe cases was 0.99 (95% confidence interval = 0.96–1.03). Adjusted RRs indicated increased risks for specific types of hypospadias with maternal non-Hispanic white race–ethnicity, higher education, older age, and nulliparity. Delivery before 37 weeks and multiple births tended either not to be associated with risk or to be associated with reduced risk. Lower birthweight was associated with increased risk for all case groups. Conclusions This study suggests that hypospadias prevalence has not been increasing in California in recent years. Differences by phenotype suggest that examining certain phenotypes separately could help to understand hypospadias etiology.