Methodological aspects of the study of dietary patterns during pregnancy and maternal and infant health outcomes. A systematic review.

The objective of the present study was to systematically review the literature exploring the associations between different dietary patterns obtained from Food Frequency Questionnaires during pregnancy and the development of health-related maternal and infant outcomes in the Framework of the EURRECA Network of Excellence. A systematic search was conducted on Pubmed for literature published up to September 2009. The search strategy resulted in an initial amount of 2048 articles. After applying the selection criteria, seven studies were finally identified. Five articles were based on prospective cohort studies and the other two were case-control studies. The methods used to elaborate the dietary pattern could be classified as hypothesis-oriented (three studies) or empirically-derived (four studies). The different food frequency questionnaires used for diet assessment were self-administered, semi-quantitative and had been previously validated, but just four studies employed questionnaires validated specifically for their use in a pregnant population. The divergent methods used to assess the dietary patterns make it difficult to compare results. However, some resulting recommendations can be applied when dietary patterns during pregnancy are analyzed: to employ a validated food frequency questionnaire designed for use in pregnancy, to consider the special role exerted by mineral and vitamin supplements in this particular population group, to adequately select the time in which dietary data is collected, to adjust the results for life-style and educational characteristics, and in the case of hypothesis-oriented dietary patterns, to correctly choose the components comprising the score.