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Study Title and Description

Coffee Consumption During Pregnancy and Birth Weight: Does Smoking Modify the Association?



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 Coffee Consumption During Pregnancy and Birth Weight: Does Smoking Modify the Association?
Author B. H. Bech, M. Frydenberg, T. B. Henriksen, C. Obel and J. Olsen
Country
Year 2015
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 10056
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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 primary aims of this study were to estimate the association between coffee intake and fetal growth and to see if smoking modifies a potential effect of coffee intake on birth weight. The association between tea and a combined caffeine variable on birth weight was also studied.
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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) In the Danish National Birth Cohort, coffee intake and smoking during pregnancy were recorded prospectively in 89,539 pregnancies that ended with live born singletons. Information on birth weight was obtained from the Danish Medical Birth Register. The exposure was coffee intake was recorded as number of cups per day (typically about 150 ml). Similar questions were asked about the intake of tea. The difference and 95% confidence interval in mean birth weight due to coffee intake was estimated by linear regression. The risk of SGA was estimated by using logistic regression. Coffee intake was categorized by number of cups per day (0, 0.5–3, 4–7, and 8+), and as number of cups in a test for trend. Analysis was done for the second and third trimesters separately. data were also analyzed according to estimated caffeine intake by using average levels of 100 mg caffeine for a cup of coffee and 50 mg for a cup of tea.
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How many outcome-specific endpoints are evaluated? 2
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Birth weight
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List additional health endpoints (separately).
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List additional health endpoints (separately)
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Notes SGA was defined as a birth weight more than two standard deviations below the mean for gestational age on the reference curve.
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Clinical Clinical
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Physiological
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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 Information on birth weight was obtained from the Danish Medical Birth Register. Birth weight is measured by healthcare professionals without knowledge of the coffee intake of the mother.
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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.) Number of cups. Coffee intake was categorized by number of cups per day (0, 0.5–3, 4–7, and 8+), and as number of cups in a test for trend.
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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) Covariates for the analyses were selected a priori as potential confounders of the association: maternal age at conception, parity, smoking, alcohol, pre-pregnancy body mass index (BMI), height, nausea, gestational age, socio-occupational status, and sex of the child. Smoking was entered in the linear regression model as a continuous variable up to 20 + cigarettes per day, age of the mother as a continuous variable up to 40 + years, BMI in 10 groups (centiles), parity in five groups (0, 1, 2, 3, and 4 + ), alcohol in three groups (tertiles), height in 10 groups (centiles), nausea in pregnancy as yes/no, socio-occupational status in three groups (high, middle, and low), and gestational week as a continuous variable until 43 + weeks. Information on coffee intake and all covariates was available for 71,000 pregnancies for the second trimester.
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Provide a general description of results (as reported by the authors). Second-trimester coffee intake was associated with reduced birth weight in a dose–response pattern for non-smokers and smokers (9 g/cup/day). Compared to non-coffee drinkers, intake of eight or more cups of coffee per day was associated with an adjusted birth weight difference of -65 g [95% confidence interval (CI) -92 to -39] for non-smokers and -79 g [95% CI -124 to -34] for women smoking more than 10 cigarettes per day. After adjustment for confounders, birth weight was reduced in a dose–response pattern with increasing coffee intake ( p < 0.001). Women drinking eight or more cups of coffee per day had a higher risk of giving birth to a child small for gestational age (adjusted odds ratio = 1.51 [95% CI 1.21–1.88]). These associations were found among both smokers and non-smokers. Using caffeine intake from both coffee and tea, results were similar to those for coffee alone. For the combined caffeine intake, almost same results were found, but test for interaction was not statistically significant for categorical or continuous caffeine variable ( p = 0.08 and p = 0.82 respectively). A total of 2.69% of the children were born SGA, and there was a dose–response association between coffee, tea, and caffeine intake and the risk of SGA. No statistically significant association was found between coffee intake of less than four cups/day compared to non-coffee drinkers and SGA. The same tendency was found for intake during the third trimester (data not shown).
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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? After adjustment for confounders, birth weight was reduced in a dose–response pattern with increasing coffee intake ( p < 0.001). There was a dose–response association between coffee, tea, and caffeine intake and the risk of SGA.
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What were the author's conclusions? The present results suggest that intake of coffee or caffeine during pregnancy is associated with reduced birth weight among both smokers and non-smokers. Whether this possible reduced fetal growth can affect child or adult health remains to be seen. The association between birth weight and intake of less than four cups per day or 300 mg caffeine is weak and exposure exceeding this level is rare in most countries. Potential long-term effects are unknown. Coffee intake during pregnancy is associated with reduced birth weight in smokers as well as non-smokers, and may increase the risk of giving birth to small for gestational age children, but the association is small for intakes of coffee of less than eight cups per day.
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What were the sources of funding? The Danish National Research Foundation has established the Danish Epidemiology Science Centre that initiated and created the Danish National Birth Cohort. The cohort is furthermore a result of a major grant from this Foundation. Additional support for the Danish National Birth Cohort is obtained from the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Health Foundation, and the Augustinus Foundation.
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What conflicts of interest were reported? Bodil Hammer Bech has received a fee for acting as a consultant in translating the section on coffee and pregnancy from this website http://coffeeandhealth.org/ to the Danish Web site www.kaffe-helbred.dk. No competing financial interests exist for other authors.
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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.  SGA: LOAEL was identified 325-775 mg/day Birth weight: 25-300 mg/day
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Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot. An OR was provided for SGA. For birth weight, none of the CIs crossed zero so lowest category selected as LOEL. These associations were found among both smokers and non-smokers. Using caffeine intake from both coffee and tea, results were similar to those for coffee alone. The same tendency was found for intake during the third trimester (data not shown).
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What is the importance of the study with respect to the adverseness of the outcome? Critcal
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