A systematic review and analysis of randomized controlled trials suggests that current dietary supplement recommendations for pregnant women may be set well below optimal levels for efficacy, raising concerns about their ability to prevent adverse maternal and infant health outcomes.
The study, published in Reproductive, Female and Child Health by Leona Cilar Budler and colleagues from the University of Maribor, Slovenia, analyzed 51 RCTs published between January 2016 and August 2023 on prenatal micronutrient supplementation. The systematic search, analysis, and synthesis were conducted between October and January 2022. Researchers searched four databases (PubMed, CINAHL with Full Text, Google Scholar, and CrossRef) and found that while existing guidelines provide essential vitamins and minerals, their effectiveness at current recommended doses remains uncertain. Using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system, 47 (92.16%) of the reviewed trials were deemed moderate quality, while 4 (7.84%) were classified as high quality.
Micronutrient deficiencies during pregnancy are linked to conception difficulties, spontaneous abortions, preterm births, low birth weight, birth defects, and long-term metabolic disorders, according to the researchers. However, the study noted gaps in rigorous monitoring of supplementation practices and identified a "dose-response conundrum" with substantial differences between potentially toxic levels and currently recommended doses.
The review focused on 13 essential vitamins and 15 minerals, with particular attention to those most commonly recommended during pregnancy: folic acid, iodine, iron, calcium, and vitamin D. Findings showed that vitamin D supplementation had some benefits for neonatal immune responses but inconsistent effects on birth outcomes. Iron and folic acid remain widely recommended, with iron linked to improved neonatal iron status but not always to better maternal health. Calcium intake in the second trimester was associated with reduced pre-eclampsia risk, while omega-3 fatty acids appeared beneficial in lowering preterm birth risk among women with low fish consumption. Magnesium deficiency was linked to preterm birth and pre-eclampsia risk, though optimal supplementation levels remain unclear.
The study concludes that micronutrient deficiencies in pregnant women pose significant risks to maternal and infant health and that current dietary supplementation recommendations require enhancement and alignment with the latest and most robust evidence. The authors specifically call for a "product recall" of existing recommendations, noting that dietary supplementation for pregnant women above the established recommendations may lead to more favorable health outcomes.
The research suggests that existing recommended dietary allowances may not fully reflect newer dose–response findings, leading to potential gaps in supplementation efficacy. The authors call for large-scale trials to refine dose recommendations and better define safe yet effective intake levels, as well as clearer communication with healthcare providers to ensure pregnant patients receive appropriate supplementation.
The authors declared no conflicts of interest.