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Water Consumption in Early Pregnancy and Risk of Spontaneous Abortion: Trihalomethanes and Other Factors

Water Consumption in Early Pregnancy and Risk of Spontaneous Abortion: Trihalomethanes and Other Factors. Shanna H. Swan, Kirsten Waller, Barbara Hopkins, Gerald DeLorenze, Gayle Windham, Laura Fenster, Catherine Schaefer, Raymond Neutra

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Water Consumption in Early Pregnancy and Risk of Spontaneous Abortion: Trihalomethanes and Other Factors

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  1. Water Consumption in Early Pregnancy and Risk of Spontaneous Abortion:Trihalomethanes and Other Factors • Shanna H. Swan, Kirsten Waller, Barbara Hopkins, Gerald DeLorenze, Gayle Windham, Laura Fenster, Catherine Schaefer, Raymond Neutra • Environmental Health Investigations BranchCalifornia Department of Health Services • Division of ResearchKaiser Permanente Medical Care Program

  2. Why was the Pregnancy Outcome Study Conducted? • To examine this association in: • A prospective study • Santa Clara and two additional areas of California (Walnut Creek and Fontana) • More recent pregnancies • Also conducted analysis of chlorination by-products.

  3. How was this Study Conducted? • Study participants were members of Kaiser Permanente HMO • Pregnant women were recruited in 1990-1991 when scheduling prenatal care • Phone interview in first trimester of pregnancy • Pregnancy outcome from medical records

  4. Study Population • N • Women contacted 7,881 • Women eligible/willing (78%) 6,179 • Interviews completed (86%) 5,342 • Pregnancy outcome determined (99%) 5,289 • Final study population* 5,144 • *Excludes ectopics, molar pregnancies and therapeutic abortions

  5. Exposure Assessment: Type and Amount of Water Consumed? • “How many glasses did you drink per day of... • cold tap water (and drinks made from cold tap water) at home?” • heated tap water (and drinks made from heated tap water) at home?” • bottled (noncarbonated) water consumed anywhere?” • carbonated water consumed anywhere?”

  6. Exposure Assessment:When in pregnancy? • Women were asked to estimate: • glasses consumed in the week beginning with the last menstrual period • glasses consumed in the week ending with the interview • when amount changed (if different) • Exposure at 8 weeks gestation used in analysis

  7. Other Water Exposure Variables • Name of water utility (confirmed by address) • How tap water was consumed: • – Straight from the tap • – Let stand before drinking • – Stored in refrigerator • – Filtered (type of filter) • Brand of bottled water • Frequency and duration of showering (and swimming)

  8. Study Population—All Study Areas • Age: less than 35 89% • Interviewed by 8 weeks gestation 64% • Pregnancy history: • Nulliparous 26% • Multiparous: 0 or 1 prior SAB 69% at least 2 prior SABs 5% • Race: White 66% Hispanic 18% • Employed during pregnancy 79% • At least some college education 68% • Any smoking in week before interview 10%

  9. Tap Water Use—All Areas • Consumption of cold tap water at home • None 37% • 0.5 - 5 53% • 6 or more 10% • Filter use (among tap water drinkers) • None 80% • Usual method of drinking tap water • Straight from the tap 58% • Refrigerate/let stand 42%

  10. Analysis (Swan et al) • “High” consumption defined as >5 glasses/day • Analyses stratified by study area • Covariates considered initially: • – Age, parity, prior SAB, body weight, race, smoking, alcohol, caffeine, education, marital status, gestational age at interview • – Water-related variables • Variables included in multivariate models: • – Age, prior SAB, body weight, race, gestational age, showering

  11. SAB Rates by Water Consumption and Study Area—Santa Clara Tap Bottled % SAB Glasses

  12. Results: Santa Clara County (Swan et al) • SAB rate among women drinking >1glass/day: • tap water only: 12.8% • bottled water only: 8.3% • Adjusted Odds Ratio =1.7 (95% CI 1.1, 2.6) • SAB rate among women drinking >5 glasses/day: • tap water only: 17.9% • bottled water only: 6.5% • Adjusted Odds Ratio = 4.6 (95% CI 2.0, 10.6)

  13. SAB Rates by Water Consumption and Study Area—Walnut Creek and Fontana Tap Bottled % SAB Glasses

  14. Conclusions (Swan et al) • Confirms increased risk of SAB in tap water drinkers in Santa Clara • Results cannot be explained by recall bias or confounding • Association not seen in two new study areas • Future studies should compare: • – tap water between utilities • – bottled water between brands

  15. Disinfection By-Products • Formed in water that is chlorinated and contains organic matter • Trihalomethanes (THM) are most prevalent by-products and include 4 compounds • Some evidence of mutagenicity and reproductive toxicity in animals, so USEPA regulates maximum contaminant levels • New studies find association with LBW

  16. Exposure Assessment for THM Levels (Waller et al) • Identified 85 drinking water utilities that served women’s residences • Obtained quarterly trihalomethane (THM) measurements from utilities • Estimated THM levels by averaging measurements throughout the utility during first trimester

  17. SAB Rate by Estimated Total THM Level in Home Tap Water During First Trimester 16 14 12 10 % SAB 8 6 4 2 0 0 1-14 15-29 30-44 45-59 60-74 75-89 90-104 105-119 >120 non-detectable Total THM Level (µg/L) a a a

  18. SAB Rate by Estimated Total THM Level and Amount of Cold Tap Water Consumed 16 14 12 10 % SAB 8 6 4 2 0 <5glasses/day TTHM >75 µg/L TTHM >75 µg/L TTHM <75 µg/L TTHM <75 µg/L >5 glasses/day <5 glasses/day >5 glasses/day Total THM Level and Amount of Water Consumed a a a

  19. SAB Rate by Region and Personal Total THM Exposure 25 20 15 % SAB 10 5 0 Santa Clara Santa Clara Walnut Creek Walnut Creek Fontana Fontana Low High Low High Low High Region and Personal Total THM Exposure — Drinking <5 glasses/day of cold tap water OR an estimated total THM level <75 µg/L Low personal exposure — Drinking >5 glasses/day of cold tap water containing an estimated total THM level >75 µg/L High personal exposure a a a

  20. SAB Rate by Estimated BDCM Level and Amount of Cold Tap Water Consumed 18 16 14 12 10 8 6 4 2 0 BDCM >18 µg/L BDCM >18 µg/L BDCM <18 µg/L BDCM <18 µg/L >5 glasses/day <5 glasses/day <5 glasses/day >5 glasses/day BDCM Level and Amount of Water Consumed a a a

  21. Study Strengths • Interviews in early pregnancy • Nearly complete follow-up of all pregnancies • Detailed information on water consumption • THM measurements specific to first trimester • Diverse study population with range of water sources and trihalomethane levels

  22. Study Weaknesses • About 25% of SABs missed • Other sources of water not ascertained • Insufficient power to look at specific utilities, bottled water brands, filters, letting water stand • Some misclassification of THM likely • THM may be markers for other chlorination by-products

  23. Regulatory Standards • Maximum Contaminant Level (MCL)Based on utility-wide average over 4 quarters • Current total THM = 100µg/L • New total THM = 80µg/L • No MCLs for individual trihalomethanes

  24. Conclusions (Waller et al) • One of the first studies to find association between total THMs and SAB • Bromodichloromethane most strongly associated • Results not explained by recall bias or confounding • Results stronger among women not employed outside the home Repeat study in other areas and obtain more precise THM assessment

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