The communication of healthy food intake via food (based dietary guidelines has shown to be more straightforward and effective than traditional single nutrient advice. Single nutrient analysis has been very successful in past in targeting specific health outcomes, well (illustrated by the discovery of folic acid’s beneficial effects in preventing offspring with neural tube defects. However, recent public health programs are aiming at improving overall dietary quality in order to prevent poor reproductive performance and adverse pregnancy outcome, and for this  approach a single nutrient focus is insufficient. Therefore, the nutrition(disease relationship needs to be understood at the level of foods as well as dietary patterns. The studies in the current thesis aim to delineate the impact of dietary patterns on pregnancy (and other reproductive outcomes, and the main objectives can be summarized as follows:

1.  To identify patterns in food intake from food frequency questionnaire data by using modern empirical statistical methods, such as principal components factor analysis and re(duced rank regression.

2.  To examine the associations between dietary patterns and several biochemical markers, e.g.
folate, vitamin B12, vitamin B6, homocysteine, S(adenosylmethionine, and S(adenosyl(homocysteine.

3.  To assess the relationship between preconceptional dietary patterns and reproductive performance
 in men and women,e.g. semen quality, fertility parameters, and chance of pregnancy.

4.  To study the effects of periconceptional maternal dietary patterns on the risk of several congenital malformations in the offspring, e.g. spinabifida, congenital heart defects, and orofacial clefts.

With the findings described in this thesis we aim to provide a better understanding of specific dietary patterns that are associated with reproductive performance and chances of pregnancy in subfertile couples.
Furthermore, new insights will be provided on to the degree in which maternal dietary patterns contribute to poor pregnancy outcomes, such as congenital malformations.