Potential Sources of Bias and Confounding in Environmental Epidemiologic Studies of Pregnancy Outcomes

Neutra, Raymond; Swan, Shanna H.; Hertz‐Picciotto, Irva; Windham, Gayle C.; Wrensch, Margaret; Shaw, Gary M.; Fenster, Laura; Deane, Margaret

doi:10.1097/00001648-199203000-00012

Cited by 25 publications

(14 citation statements)

References 3 publications

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“…We found no evidence of information bias among women with a history of miscarriage, as suggested by Neutra et al (1992) . The average water consumption reported by women with one or more miscarriages was similar to that reported by women with no prior miscarriages.…”

Section: Discussioncontrasting

confidence: 56%

“…Changes in water use patterns and risk factors for adverse pregnancy outcomes were assessed by asking about behavioral modifications that occurred after becoming pregnant. Finally, the potential for information bias in reporting exposures to water was assessed by incorporating a history of prior spontaneous abortion, level of concern about environmental hazards, and the method of interview in stratified analyses (Neutra et al, 1992 ) .…”

Section: Questionnairesmentioning

confidence: 99%

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Exposure to tap water during pregnancy

Zender

Bachand

Reif

2001

J Expo Sci Environ Epidemiol

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Studies of disinfection byproducts ( DBPs ) in drinking water and risk of adverse reproductive outcome have usually relied on approximate measures of exposure. Individual differences in consumption of bottled or filtered water, variability in tap water consumption at home and at work, dermal and inhalation exposure to volatile contaminants, and changes in residency during pregnancy may lead to exposure misclassification. We characterized exposures to tap water and other risk factors among 71 pregnant and 43 non -pregnant women attending public health clinics. Nearly all residences had a municipal water source, but 25% of women drank filtered or bottled water. Fifty percent of the women in our sample reported working outside the home where, on average, one third of their daily water intake took place. Pregnant women consumed more water than non -pregnant women ( 3.4 vs. 3.0 total l / day ) , especially cold tap water at home ( 1.8 vs. 1.3 l / day, 95% CI for the difference = 0.1, 0.9 ) . Patterns of showering were similar for both groups of women, but pregnant women were more likely to bathe and to bathe more frequently. The prevalence of smoking was lower among pregnant women ( 22.5% vs. 32.6% ) , as was the consumption of alcohol ( 4.2% vs. 53.5%, 95% CI for the difference = À 64.9, À 33.7 ) . Thirty -two percent of women had moved during their current pregnancy. The data reaffirm the importance of collecting individual -level data for water consumption and exposure to potential confounders to avoid misclassification bias. This study is the first to target women of low socio -economic status ( SES ) and therefore of particular interest in studies of adverse reproductive outcomes for which this group is at increased risk.

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Section: Discussioncontrasting

confidence: 56%

Section: Questionnairesmentioning

confidence: 99%

Exposure to tap water during pregnancy

Zender

Bachand

Reif

2001

J Expo Sci Environ Epidemiol

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“…There was no trend between the occupational exposure level and the risk of ectopic pregnancy. Furthermore, if there had been recall bias, it is likely that it would have been an undel~eporting of exposure among the referents, and it could not explain our results (18,19). The level of the exposure of women working in hospitals may be too low nowadays to cause a substantial increase in ectopic pregnancy risk.…”

Section: Discussionmentioning

confidence: 85%

Ectopic pregnancy and occupational exposure of hospital personnel

Bouyer

Saurel‐Cubizolles²,

Grenier³

et al. 1998

Scand J Work Environ Health

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“…In our study, we avoided the selection bias and information bias inherent to interview studies of pregnancy outcome and environmental exposure (19,20) by using actual measurements of exposure and by obtaining data on end points from registry-based information systems.…”

Section: Discussionmentioning

confidence: 99%

Chernobyl fallout and outcome of pregnancy in Finland.

Auvinen

Vahteristo²,

Arvela³

et al. 2001

Environ Health Perspect

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Possible effects of Chernobyl fallout on outcome of pregnancy in Finland were evaluated in a nationwide follow-up study. The outcomes were the rate of live births and stillbirths, pregnancy loss, and induced abortions by municipality. Exposure was assessed based on nationwide surveys of radiation dose rate from the Chernobyl fallout, from both external and internal exposures. Using these measurements, we estimated the monthly dose rate for each of the 455 Finnish municipalities. On average, the dose rate from Chernobyl fallout reached 50 microSv per month in May 1986--a doubling of the natural background radiation. In the most heavily affected area, 4 times the normal background dose rates were recorded. Given the underlying regional differences in live birth, stillbirth, and abortion rates, we used longitudinal analysis comparing changes over time within municipalities. A temporary decline in the live birth rate had already begun before 1986, with no clear relationship to the level of fallout. A statistically significant increase in spontaneous abortions with dose of radiation was observed. No marked changes in induced abortions or stillbirths were observed. The decrease in the live birth rate is probably not a biological effect of radiation, but more likely related to public concerns of the fallout. The effect on spontaneous abortions should be interpreted with caution, because of potential bias or confounding. Further, there is little support in the epidemiologic literature on effects of very low doses of radiation on pregnancy outcome.

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Potential Sources of Bias and Confounding in Environmental Epidemiologic Studies of Pregnancy Outcomes

Cited by 25 publications

References 3 publications

Exposure to tap water during pregnancy

Exposure to tap water during pregnancy

Ectopic pregnancy and occupational exposure of hospital personnel

Chernobyl fallout and outcome of pregnancy in Finland.

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