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Study Title and Description

Maternal caffeine consumption during pregnancy and the risk of miscarriage: a prospective cohort study.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on reproductive and developmental outcomes?
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Primary Publication Information
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TitleData
Title Maternal caffeine consumption during pregnancy and the risk of miscarriage: a prospective cohort study.
Author X Weng,R Odouli,DK Li,
Country
Year 2008
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Reproductive Toxicity - Design Details
Arms
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Design Details
Question... Follow Up Answer Follow-up Answer
Refid 18221932
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What outcome is being evaluated in this paper? Reproductive and Development
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What is the objective of the study (as reported by the authors)? The objective of this population-based prospective study was to examine the effect of maternal caffeine intake during pregnancy on the risk of miscarriage, taking into account a number of potential confounders, especially the impact of nausea or vomiting during pregnancy.
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Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) The study was conducted among pregnant members of the Kaiser Permanente Medical Care Program (KPMCP), any woman who submitted a urine or blood sample for a pregnancy test was contacted. Pregnancy test used to confirm. Information on exposure to caffeine consumption during pregnancy was obtained during an in-person interview conducted soon after a woman’s pregnancy was confirmed (the median gestational age at interview was 71 days). They were asked about the types of their drinks; timing of initial drink; the frequency and amount of the intake; whether they changed consumption patterns since becoming pregnant; and, if so, the time, the frequency, and the amount of consumption after the change. We used the following conversion factors to estimate the amount of caffeine intake: for every 150 mL of a beverage, we estimated 100 mg for caffeinated coffee, 2 mg for decaffeinated coffee, 39 mg for caffeinated tea, 15 mg for caffeinated soda, and 2 mg for hot chocolate. Pregnancy outcomes up to 20 weeks of gestation were determined for all participants through the following 3 methods: (1) searching the KPMCP inpatient or outpatient databases, (2) reviewing medical records, and (3) contacting participants whose outcomes could not be determined by using the previous 2 methods. The Cox proportional hazards regression was used to take into account possible differing gestational ages at study entry between the exposed (caffeine intake) and unexposed. The average daily caffeine intake during pregnancy was categorized as 0, less than 200 mg/day, or 200 or more mg/day in the overall analysis. Potential confounders, such as maternal age, race, education, household income, marital status, smoking, alcohol consumption, Jacuzzi use, MF exposure, and nausea and vomiting were included into the COX model for adjustment. A test for trend was performed with the categories of caffeine intake as an ordinal scale.
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How many outcome-specific endpoints are evaluated? 1
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Miscarriage (SA)
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List additional health endpoints (separately).
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List additional health endpoints (separately)
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Notes
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Clinical Clinical
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Physiological
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Other Other
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What is the study design? Cohort
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Randomized or Non-Randomized?
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What were the diagnostics or methods used to measure the outcome? Objective
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Optional: Name of Method or short description Pregnancy outcomes up to 20 weeks of gestation were determined for all participants through the following 3 methods: (1) searching the KPMCP inpatient or outpatient databases, (2) reviewing medical records, and (3) contacting participants whose outcomes could not be determined by using the previous 2 methods.
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Caffeine (general) Caffeine (general)
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Coffee Coffee
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Chocolate
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Energy drinks
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Gum
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Medicine/Supplement
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Soda Soda
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Tea Tea
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Measured
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Self-report Self-report
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Children
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Adolescents
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Adults
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Pregnant Women Pregnant Women
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Caffeine: 0, <200, >/=200 mg/day
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) Potential confounders, such as maternal age, race, education, household income, marital status, smoking, alcohol consumption, Jacuzzi use, MF exposure, and nausea and vomiting were included into the COX model for adjustment.
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Provide a general description of results (as reported by the authors). An increasing amount of caffeine intake was associated with an increased risk of miscarriage. Compared with nonusers, women who consumed 0-200 mg caffeine daily had an increased risk of miscarriage (15% vs 12%), and the corresponding risk was much greater (25%) among women who consumed more than 200 mg caffeine daily. After adjustment for potential confounders including maternal age, race, education, household income, marital status, previous miscarriage, smoking, alcohol consumption, Jacuzzi use, MF exposure, and nausea and vomiting, the hazard ratio of miscarriage was 1.42 (95% confidence interval [CI], 0.93 to 2.15) and 2.23 (95% CI, 1.34 to 3.69) for daily caffeine consumption of 0-200 mg and 200 mg or more, respectively (P for trend = .01). We performed a stratified analysis according to the source of caffeine, and the association remained, regardless of the sources. Caffeine intake of 200 mg or greater remained associated with an increased risk of miscarriage, regardless of whether a woman changed her pattern of caffeine intake after pregnancy, although the estimate in each stratum was no longer statistically significant because of reduced sample size from stratification. The association existed among women both with and without the symptom of nausea during pregnancy, although the association was slightly stronger among women with the symptom. The effect of caffeine consumption on miscarriage was higher in the nonsmoker group (adjusted hazard ratio [aHR] 2.04, 95% CI, 1.35 to 3.09) than the smoker group (aHR 1.49, 95% CI, 0.36 to 6.08) and was only statistically significant in the nonsmoker group.
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Did the authors perform a dose-response analysis (or trend/related analysis)? Yes
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What were the authors's observations re: trend analysis? The hazard ratio of miscarriage was 1.42 (95% confidence interval [CI], 0.93 to 2.15) and 2.23 (95% CI, 1.34 to 3.69) for daily caffeine consumption of 0-200 mg and 200 mg or more, respectively (P for trend = .01).
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What were the author's conclusions? In conclusion, the results from our prospective cohort study supported previous findings that high caffeine consumption during pregnancy may increase the risk of miscarriage. We provided new evidence that the observed association was not likely the result of confounding by the pregnancyrelated symptoms of nausea, vomiting, and aversion to caffeine consumption. Therefore, it may be prudent to stop or reduce caffeine intake during pregnancy.
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What were the sources of funding? This study was supported in part by the California Public Health Foundation.
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What conflicts of interest were reported? None reported
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Does the exposure (dose) need to be standardized to the SR? No
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Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).
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List all the endpoint(s) followed by the dose (mg) which will be used in comparison to Nawrot.  Characterize value as LOAEL/NOAEL, etc. if possible.  Miscarriage (SA) LOAEL = >/= 200 mg/day
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Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot. Adjusted OR = 1.42 (95% confidence interval [CI], 0.93 to 2.15) and 2.23 (95% CI, 1.34 to 3.69) for daily caffeine consumption of 0-200 mg and 200 mg or more, respectively (P for trend = .01)
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What is the importance of the study with respect to the adverseness of the outcome? Critcal
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