Consumption of chocolate in pregnant women and risk of preeclampsia: a systematic review

Background Previous studies have been limited in reporting the association between chocolate consumption, measured by interviewer-administered questionnaire or serum theobromine, a biomarker for cocoa, and risk of preeclampsia, and have showed somewhat conflicting results. Methods/Design A systematic review of observational and experimental studies will be carried out. We will examine PubMed, Embase, and the entire Cochrane Library. Studies of chocolate consumption compared or not with placebo or low flavanol chocolate during pregnancy will be evaluated to investigate the effect of chocolate consumption in pregnant women on the risk of preeclampsia or pregnancy-induced hypertension. Screening for inclusion, data extraction, and quality assessment will be performed independently by two reviewers in consultation with a third reviewer. Validity of the studies will be ascertained by using the Cochrane Collaboration’s tool. Relative risk of preeclampsia will be the primary measure of treatment effect. Heterogeneity will be explored by subgroup analysis according to confounding factors and bias. Discussion This systematic review will contribute to establish the current state of knowledge concerning the possible association between chocolate consumption and prevention of preeclampsia. Furthermore, it will justify if additional experimental trials are necessary to better evaluate the benefits of chocolate consumption on the risk of preeclampsia. Trial registration This systematic review has been registered in the PROSPERO international prospective register of systematic reviews. The registration number is: CRD42013005338


Strategy combining
Concepts identified Other words and spelling variations Pregnant women Synonyms MeSH Table 7  Endothelium  Endotheliums Blood pressure

Interventions
No.

5.1
StudyID ID number data extraction (number) Continuous

5.2
Exposure Exposure assessment (name) Nominal

5.3
TimingF Timing of exposure in 1 st trimester evaluated in days (number) Continuous

5.4
TimingT Timing of exposure in 3 rd trimester evaluated in days (number) Continuous

5.5
Technique Technique used for quantification of theobromine concentration in serum (name) Nominal

5.6
Detection Limit of detection of theobromine (ng/dl) (number) Continuous

5.9
Theobromine concentration in 1 st trimester

5.11
Total women by theobromine quartile in 1 st trimester

TQuartile1F
Total women in 1 st quartile of theobromine concentration in 1 st trimester (number) Categorical

TQuartile2F
Total women in 2 nd quartile of theobromine concentration in 1 st trimester (number) Categorical

TQuartile3F
Total women in 3 rd quartile of theobromine concentration in 1 st trimester (number) Categorical

TQuartile4F
Total women in 4 th quartile of theobromine concentration in 1 st trimester (number) Categorical

5.12
Total women by theobromine quartile in 3 rd trimester

TQuartile1T
Total women in 1 st quartile of theobromine concentration in 3 rd (number) Categorical trimester

TQuartile2T
Total women in 2 nd quartile of theobromine concentration in 3 rd trimester (number) Categorical

TQuartile3T
Total women in 3 rd quartile of theobromine concentration in 3 rd trimester (number) Categorical

TQuartile4T
Total women in 4 th quartile of theobromine concentration in 3 rd trimester (number) Categorical

5.15
Total women by number of servings of chocolate drinks and foods consumed per week in 3 rd trimester

T<1T
Less than 1 serving of chocolate drinks and foods consumed per week in 3 rd trimester (number) Categorical

ToccT
Occasional consumption of chocolate drinks and foods in 3 rd trimester (1 to 3-4 servings per week) (number) Categorical

TregT
Regular consumption of chocolate drinks and foods in 3 rd trimester (4-5 or more servings per week) (number) Categorical

5.16
Source Source of chocolate (name) Nominal

5.17
Caffeine Assessment of consumption or cord concentration (Y:Yes, N:No) Dichotomous

Outcomes
No.

6.1
StudyID ID number data extraction (number) Continuous

6.3
Cases Number of cases with preeclampsia (number) Continuous

6.4
Total cases by quartiles of theobromine concentrations in 1 st trimester

CQuartile1F
Total cases in 1 st quartile of theobromine concentration in 1 st trimester (number) Categorial

CQuartile2F
Total cases in 2 nd quartile of theobromine concentration in 1 st trimester (number) Categorial

CQuartile3F
Total cases in 3 rd quartile of theobromine concentration in 1 st trimester (number) Categorial

CQuartile4F
Total cases in 4 th quartile of theobromine concentration in 1 st trimester (number) Categorial

6.5
Total cases by quartiles of theobromine concentrations in 3 rd trimester

CQuartile1T
Total cases in 1 st quartile of theobromine concentration in 3 rd trimester (number) Categorial

CQuartile2T
Total cases in 2 nd quartile of theobromine concentration in 3 rd trimester (number) Categorial

CQuartile3T
Total cases in 3 rd quartile of theobromine concentration in 3 rd trimester (number) Categorial

CQuartile4T
Total cases in 4 th quartile of theobromine concentration in 3 rd trimester (number) Categorial

6.6
Total cases by categories of chocolate consumption in 1 st trimester