Diet, Preconception and Pregnancy · Specialty diets, nutritional supplementation and the metabolic preparation for conception

Nutrition relevant to pregnancy begins before a positive pregnancy test. Maternal folate status, iron stores, vitamin B12 status, iodine exposure, metabolic health and dietary behaviour are established before fertilisation and implantation. Several critical embryological processes occur before many women recognise pregnancy, making the preconception interval a genuine biological window rather than merely a planning period.[1,2,12] Among whole-diet strategies, the Mediterranean dietary pattern currently has the most coherent evidence base. A 2026 systematic review and meta-analysis of 33 studies, including 19 randomised trials and more than 180,000 pregnancies, reported lower risks of gestational diabetes, preterm delivery, low neonatal weight and fetal-growth abnormalities with greater adherence or intervention, although evidence for pre-eclampsia and several other endpoints remained inconsistent.[4] That evidence should not be converted into a claim that a Mediterranean diet—or any other diet—constitutes an infertility treatment. The 2026 systematic review of nutrition in assisted reproductive technology concluded that healthy patterns are reasonable and potentially advantageous, but no specific diet has consistently demonstrated improvement in live birth.