International expert consensus on micronutrient supplement use during the early life course
BMC Pregnancy and Childbirth volume 25, Article number: 44 (2025)
Irene Cetin, Roland Devlieger, Erika Isolauri, Rima Obeid, Francesca Parisi, Stefan Pilz, Lenie van Rossem, Maternal Nutrition Delphi Study Group & Régine Steegers-Theunissen
Background
Growing evidence demonstrates that maternal nutrition is crucial for the health of the mother-to-be, and early life course of the offspring. However, for most micronutrients, guidelines are inconsistent. This Delphi study aimed to investigate the level of expert consensus on maternal nutrition and micronutrient needs during preconception, pregnancy and lactation.
Methods
We conducted a two-round web-based Delphi survey on various topics including general approaches to diet and supplement use, and existing guidelines. For the periods of preconception, pregnancy and lactation, questions focused on the importance and strength of evidence for supplement use with the following micronutrients for low- and high-risk populations: folic acid, choline, iodine, magnesium, calcium, iron, selenium, docosahexaenoic acid (DHA), and vitamins B1, B2, B6, B12, D and K.
Results
Thirty-five experts participated in the panel, who were healthcare professionals (HCPs), researchers and joint HCP-researchers with expertise in nutrition, gynaecology and/or obstetrics. Panellists reached consensus on the importance of diet and dietary supplement use during pregnancy and agreed on the lack of clarity and consistency in current guidelines, and the need for education in these areas for HCPs, pregnant people and the general population. For general low-risk populations, there was consensus on the importance of supplement use with iron and vitamin D from preconception through lactation, with folic acid and iodine from preconception through the second and third trimesters, respectively, with DHA from the first trimester through lactation and with calcium during lactation. Panellists agreed that the evidence for supplement use with each of these micronutrients during these phases to improve outcomes and/or foetal development is strong, except for vitamin D (preconception), DHA (first trimester), and iron (both periods). There was also consensus that supplement use advice should be tailored for people following vegan/vegetarian diets, restricted diets due to food intolerances, obesity, polycystic ovary syndrome, diabetes mellitus, and previous nutrition-related pregnancy complications.
Conclusion
The findings revealed robust consensus on various aspects of maternal nutrition, including the need for education, the lack of consistency in current guidelines on supplement use, the importance of supplement use across specific phases of pregnancy and the at-risk groups requiring tailored approaches.
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Vitamin D section of PDF
There was consensus agreement on the importance of vitamin D supplement use in the preconception phase, across all three trimesters of pregnancy and throughout the lactation period. In agreement with these recommendations, the strength/quality of evidence arguing for vitamin D supplement use to improve maternal and/or foetal/infant health was also rated as somewhat to very strong, except for the preconception period. This strong consensus in favour of widespread vitamin D supplement use may not sufficiently reflect the still ongoing scientific discussion on vitamin D in these settings [86,87,88].
There is compelling evidence that a poor vitamin D status, reflected by low serum 25(OH)D concentrations, is associated with various adverse pregnancy outcomes [86]. In contrast, data from vitamin D RCTs are inconsistent and often limited due to low sample sizes, enrolment starting after the first trimester, and/or including women with a sufficient vitamin D status [87, 88]. While it is beyond the scope of this manuscript to critically appraise the whole literature on vitamin D, widespread vitamin D supplement use is supported by evidence that
- (a) vitamin D deficiency is very common,
- (b) vitamin D is critical for bone health (i.e. prevention and treatment of rickets and osteomalacia) as consistently documented by evidence-based guidelines, and
- (c) vitamin D supplement use at moderate doses (e.g. 800–2000 IU, 20–50 µg daily) is relatively safe from preconception throughout pregnancy until lactation [86, 89].
There are also additional potential beneficial effects of vitamin D, such as for fertility, preventing pre-eclampsia or gestational diabetes mellitus, although evidence remains limited [86, 87, 90].