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S H Swan

Publications and source records attributed to S H Swan.

At least 55 records · Page 3Linked to original sources
PubMed1992

Parental cigarette smoking and the risk of spontaneous abortion.

Although cigarette smoking is often considered a risk factor for spontaneous abortion, the epidemiologic literature is actually inconsistent. Therefore, the authors examined maternal and paternal smoking and maternal passive smoke exposure using data from a large case-control study of spontaneous abortion (626 cases and 1,300 controls) conducted in Santa Clara County, California, in 1986 and 1987. No excess risk of spontaneous abortion was seen in the 1% of women who smoked an average of more than 20 cigarettes per day in the first trimester. Moderate smokers (11-20 cigarettes per day) had a slightly elevated crude odds ratio of 1.3 (95% confidence interval 0.9-1.9), which was close to unity after adjustment for covariates. Paternal smoking showed a slight crude elevation for moderate and heavy smoking, but no association after adjustment. In contrast, maternal exposure to environmental tobacco smoke for 1 hour or more per day was associated with spontaneous abortion, even after adjustment (odds ratio = 1.5, 95% confidence interval 1.2-1.9). For both maternal direct and environmental exposure, the association appeared to be stronger in second-trimester abortions. Several studies have found stronger associations of smoking with late versus early abortions, perhaps reflecting smoking-associated placental insufficiency and fetal hypoxia.

Abortion, Spontaneous↗
PubMed1992

Reproductive outcomes in relation to malathion spraying in the San Francisco Bay Area, 1981-1982.

We studied reproductive outcomes in a cohort of 7,450 pregnancies identified through three Kaiser-Permanente facilities in the San Francisco Bay Area, in relation to exposure to the pesticide malathion, applied aerially to control an infestation by the Mediterranean fruit fly. We included in the cohort all women over age 17 who were registered at these facilities and who were confirmed as pregnant during the spraying period. Residence histories throughout the pregnancy were obtained by mailed questionnaire or telephone interview from 933 women with adverse outcomes and a sample of 1,000 women with normal outcomes, and were converted to geographical coordinates. We linked the coordinates for malathion spraying corridors with the residence coordinates to create individual exposure indices for each week of pregnancy. The statistical analysis compared each of the adverse pregnancy outcome groups against an appropriate control group using logistic regression or survival time regression approaches. After adjustment for various confounders, no important association was found between malathion exposure and spontaneous abortion, intrauterine growth retardation, stillbirth, or most categories of congenital anomalies. Gastrointestinal anomalies were related to second trimester exposure (odds ratio = 2.6), based on 13 cases and not specific to any particular International Classification of Diseases code.

Abnormalities, Drug-Induced↗
PubMed1992

Is drinking water related to spontaneous abortion? Reviewing the evidence from the California Department of Health Services Studies.

Because preliminary data suggested a relation between risk of spontaneous abortion and tapwater consumption during pregnancy, the California Department of Health Services included questions on prenatal water consumption in all reproductive studies conducted between 1982 and 1988. Results from four of these five retrospective data bases suggest that women abstaining from tapwater or drinking bottled water during the first trimester of pregnancy may be at reduced risk of spontaneous abortion. Fetal resorption frequencies seen in an accompanying toxicology study were consistent with these epidemiologic findings, although not conclusive. Tap and bottled water samples from these study areas were analyzed for agents that might account for these findings. Differences in trace element composition and biological activity were observed, but the reproductive significance of these differences is unknown. This paper presents an overview of these studies, which are presented in detail separately. Three alternative explanations for these findings--bias, chance, and causality--are reviewed.

Abortion, Spontaneous↗
PubMed1992

Adverse pregnancy outcomes in relation to water consumption: a re-analysis of data from the original Santa Clara County Study, California, 1980-1981.

Residents of a census tract that received drinking water from a well contaminated with solvents were previously shown to experience a spontaneous abortion rate over twice that occurring in an unexposed census tract. In addition, the rate of birth defects in the exposed tract was three times that in the unexposed tract. Surprisingly, increased tapwater consumption was associated with higher rates of spontaneous abortions in both the exposed and the unexposed tracts. Subsequent studies in this area have investigated the relation between spontaneous abortions and consumption of tapwater in more detail. In this report, data from the original study have been re-analyzed using methods comparable with those used in more recent studies. These results confirm the association between spontaneous abortions and reported cold tapwater consumption that was seen in the original study. The observed effect was not due to maternal risk factors, nor was it a function of consumption of bottled water. After controlling for bottled water, the odds ratio for consumption of tapwater was 3.4 (95% confidence interval = 0.6-19.4).

Abortion, Spontaneous↗
PubMed1992

Spontaneous abortions and birth defects related to tap and bottled water use, San Jose, California, 1980-1985.

We recently studied pregnancies occurring during 1980-1985 in four study areas in Santa Clara County, California. Two of the areas were exposed to solvent-contaminated drinking water during 1980 and 1981, and two were unexposed. There was an overall excess of spontaneous abortions among women who reported any tapwater consumption during the first trimester of pregnancy compared with those who reported no tapwater consumption [odds ratio (OR) = 4.0; 95% confidence interval (CI) = 1.8-9.1)], regardless of exposure to the contaminated water. The odds ratio for spontaneous abortion for women reporting any vs no tapwater was 6.9 (95% CI = 2.7-17.7) after adjustment for numerous potential confounders using multiple logistic regression analyses. The elevated odds ratio of spontaneous abortion was seen among tapwater drinkers who used no filters or softener-type filters but not among women who reported use of active filters. Spontaneous abortion rates were reduced in women who reported any vs no bottled water consumption (OR = 0.26; 95% CI = 0.16-0.43). Among women who reported no tapwater consumption, no birth defects occurred among 263 live births; in comparison, among women who reported tapwater consumption, 4% of 908 live births had defects (P = 0.0001). We observed no relation between birth defects and bottled water use.

Abortion, Spontaneous↗
PubMed1992

Reporting bias and mode of interview in a study of adverse pregnancy outcomes and water consumption.

In an earlier publication, it was shown that consumption of tapwater during the first trimester of pregnancy was associated with a risk of spontaneous abortion among women who attended three prenatal clinics located in northern California between September 1981 and June 1982. Evidence for biased recall was presented. This report demonstrates that the association is limited to women interviewed by telephone and is not observed among those who completed a mail questionnaire. The possibility that the association among women interviewed by telephone is causal and that the lack of association among mail respondents is due to bias, confounding, or apparently chance fluctuations is shown to be unlikely. For instance, the probability is low that, among mail respondents, cases underreported exposure as compared with controls or that random errors were common enough to camouflage a true effect. Demographic differences between mail and telephone respondents also do not explain the results. Interviewers were, however, aware of the outcome of the pregnancy, suggesting that differential reporting of exposure may have been stimulated in the nonblind telephone interview. The pattern of heterogeneity between mail and telephone respondents was also observed for reportable anomalies and tapwater consumption. The data on heterogeneity support the previously published conclusion that differential reporting (biased recall) of this common exposure, tapwater consumption, is the likely explanation for its observed association with the risk of spontaneous abortion. That this association is limited to telephone respondents elucidates the mechanism that apparently produced the bias: that is, the medium of nonblind telephone interviews.

Abortion, Spontaneous↗
PubMed1992

Tap or bottled water consumption and spontaneous abortion: a 1986 case-control study in California.

To investigate whether drinking tap or bottled water during pregnancy affects the risk of spontaneous abortion, we asked questions about water consumption in a large case-control study (626 cases, 1,300 controls). The study ascertained cases from hospital pathology laboratory reports of pregnancies that began in 1986 and obtained controls from birth certificates. The crude odds ratio for consumption of any vs no cold tapwater at home during the first trimester was 1.2 (95% confidence interval = 1.0-1.5), with no dose-response effect. The crude odds ratio for any bottled water consumption was 0.79 (95% confidence interval = 0.65-0.96), with a downward trend by amount consumed. Adjusting for many potential confounders did not alter these associations appreciably, although some variables appeared to be effect modifiers. The point estimates were stronger among women who were more difficult to contact, suggesting the possibility of bias.

Abortion, Spontaneous↗
PubMed1992

Tap or bottled water consumption and spontaneous abortion in a case-control study of reporting consistency.

A recent case-control study of 1,926 women found a slightly increased risk of spontaneous abortion associated with reported consumption of tapwater and a decreased risk with reported consumption of bottled water. In a case-control study of spontaneous abortion designed to examine the consistency of prenatal exposure reporting, the association of spontaneous abortion with tap or bottled water consumption was also examined. Cases of spontaneous abortion (N = 100) were ascertained from hospital pathology reports, and pregnant controls (N = 200) were obtained from obstetrical appointment logs. Subjects were first interviewed approximately 24 weeks after their last menstrual period and again approximately 48 weeks after their last menstrual period. Neither an increased risk for spontaneous abortion associated with consumption of tapwater nor a protective effect for consumption of bottled water was observed. Changes in reporting of tapwater consumption from the first to the second interview suggest the possibility of differential reporting in cases and controls. There was no evidence suggesting biased reporting of bottled water consumption.

Abortion, Spontaneous↗
PubMed1992

The effects of water source on reproductive outcome in Fischer-344 rats.

To investigate the relation between maternal water consumption and pregnancy loss, we conducted a reproductive toxicology study using Fischer rats. On day 0 of gestation, dams were assigned to tapwater, commercial bottled water, or purchased high pressure liquid chromatography grade water. On day 20 of gestation, we killed the dams and removed their litters for examination. There were no marked effects of dietary water source on maternal body weight, number of implantation sites, number of live fetuses, sex of offspring or number of resorptions per litter. Fetal length and weight, placenta weight, and soft tissue and skeletal malformations were also similar among groups. The tapwater group had somewhat higher resorption frequency (5.3%) and frequency of affected fetuses (6.5%) than those fed bottled water (3.8% and 4.5%, respectively).

Animals↗
PubMed1992

Potential sources of bias and confounding in environmental epidemiologic studies of pregnancy outcomes.

Biases familiar to all epidemiologists take on new importance when studying spontaneous abortion because of the significance of the timing of exposure during gestation, and because the gestational age at which the pregnancy is recognized may be related to risk factors under study. In this paper, we systematically review the principal biases that might affect epidemiologic studies of pregnancy loss, in the context of a series of studies that found associations between adverse reproductive outcomes and prenatal use of tap or bottled water. These biases relate to availability of subjects for study, exposure opportunity, recall of exposure, recall of disease, and confounding. In one of the studies, the rate of bottled water use changed dramatically over the course of the study period, providing an opportunity to test indirectly for biased recall of exposure. We conclude that a less complete recall of water intake among women with normal pregnancies, as compared with those with spontaneous abortions, may have produced, or increased the magnitude of, the associations seen in these studies.

Bias↗
PubMed1992

Reporting and selection bias in case-control studies of congenital malformations.

Retrospective studies of congenital malformations frequently rely on exposures reported by study subjects. Differential error in exposure reporting by cases and controls, which has alternatively been referred to as "recall bias" and "reporting bias," may result in a biased effect measure. Some authors have attempted to avoid reporting bias by comparing exposures between two malformed groups, rather than between cases and nonmalformed controls. This approach, however, may introduce its own bias, which we call selection bias. Both reporting bias and selection bias are shown to be algebraically equivalent to bias arising from exposure misclassification. The magnitudes of these biases are compared for a range of plausible parametric values. The case-control design is sensitive to both differential reporting and selection bias, and the choice of study design involves balancing these two sources of bias.

Case-Control Studies↗
PubMed1992

Moderate maternal and paternal alcohol consumption and the risk of spontaneous abortion.

Maternal alcoholism can lead to the fetal alcohol syndrome in offspring, but the effect of more moderate alcohol consumption during pregnancy remains an issue of concern. Therefore, we analyzed data from a large case-control study of spontaneous abortion (626 cases, 1,300 controls) that ascertained maternal alcohol consumption before and during pregnancy, as well as paternal consumption. Asking when in pregnancy alcohol consumption changed allowed us to calculate a weighted average of the amount consumed weekly during the first trimester. The odds ratio for consumption of seven or more drinks per week was 1.9 [95% confidence interval (CI) = 1.1-3.4] when adjusted for maternal smoking, passive smoking, and maternal age. Data were too sparse to examine higher consumption levels. There was some evidence that cases may have had less opportunity than controls to decrease consumption during their shorter pregnancies, potentially biasing the odds ratio upward. The adjusted odds ratio for any paternal alcohol consumption was 1.2 (CI = 0.93-1.5), with no dose-response effect seen. Among pregnancies in which the mother did not drink, there was no association with paternal drinking.

Abortion, Spontaneous↗
PubMed1991

Assessment of reporting consistency in a case-control study of spontaneous abortions.

Reporting consistency was examined in a case-control study of spontaneous abortion in Santa Clara County, California. Each case (n = 100) and two pregnant controls (n = 200), frequency-matched by last menstrual period, were interviewed twice: first after the case's spontaneous abortion (on average, 24 weeks after the last menstrual period) and again after completion of the controls' pregnancies (on average, 48 weeks after the last menstrual period). Because of concern about differential reporting of water consumption in regions with publicized water contamination, interviews included detailed questions about consumption of tap water and bottled water during pregnancy, as well as other exposures. Most factors such as caffeine consumption, cigarette smoking, employment, and pregnancy history were consistently reported between interviews and did not appear to be subject to differential reporting between cases and controls. When variables were examined by univariate analysis, controls deleted reports of tap water consumption (any vs. more) more often than did cases. There was also a suggestion of differential reporting of up to two glasses per day for tap water and bottle water consumption when they were examined as continuous variables. However, the degree of differential reporting was not sufficient to appreciably alter the measures of association between water consumption during pregnancy and spontaneous abortion.

Abortion, Spontaneous↗
PubMed1991

Exposure to organic solvents and adverse pregnancy outcome.

In a large case-control study (n = 1,926) of spontaneous abortion (SAB), exposure to solvents was ascertained by a telephone interview that asked about occupational use of 18 specific solvents or products, as well as an open-ended "other" solvent category. The adjusted odds ratio for use of any solvent was 1.1 (0.8, 1.5). Solvents for which at least a doubled crude risk of SAB was found included perchlorethylene (OR = 4.7, 95% CI = 1.1, 21.1), trichloroethylene (OR = 3.1, CI = 0.9, 10.4), and paint thinners (OR = 2.3, CI = 1.0, 5.1). Comparing exposure greater than 10 hours per week versus less did not show consistent dose-response effects. By solvent class, an association was seen with aliphatic solvents (adjusted OR = 1.8, 95% CI = 1.1, 3.0), but there was no dose-response effect by hours of use. Household use of solvent-containing products was generally not strongly associated with SAB, nor did it appear to confound the association seen with occupational use. From this and other studies, occupational exposure to at least some solvents appears associated with SAB. The associations of solvent exposure and fetal growth among liveborn offspring of controls was also examined.

Abortion, Spontaneous↗
PubMed1991

Caffeine consumption during pregnancy and spontaneous abortion.

We conducted a case-control study of spontaneous abortion in Santa Clara County, California between 1986 and 1987. We analyzed data on 607 cases and 1,284 controls to evaluate the potential association between caffeine consumption during the first trimester of pregnancy and spontaneous abortion. About 70% of the women consumed caffeinated coffee, tea, and/or soda; 7% of the women consumed more than an average of 300 mg of caffeine daily. The crude odds ratio (OR) for heavy caffeine consumption (greater than 300 mg/day) was 1.55 (95% CI: 1.04-2.31), which decreased to 1.22 (95% CI: 0.80-1.87) after controlling for confounding factors. For these heavy users, nausea modified the association of spontaneous abortion and caffeine; heavy caffeine consumers reporting nausea had a doubled risk for spontaneous abortion (adjusted OR = 2.10, 95% CI: 1.20-3.70), in contrast to those who did not report nausea (adjusted OR = 0.53, 95% CI: 0.27-1.04). Heavy caffeine consumers who decreased their caffeine intake early in pregnancy had a risk of spontaneous abortion similar to that of nonconsumers.

Abortion, Spontaneous↗