Analysis of 5,408 pregnant women across 10 countries reveals that maternal folate deficiency increases low birth weight risk by 22%, while combined folate and vitamin B12 deficiencies amplify this risk to 38%. Unexpectedly, iron deficiency alone without B12 deficiency appeared protective, reducing low birth weight risk by 60%. These findings illuminate how micronutrient interactions during pregnancy may be more complex than individual vitamin effects suggest. The research challenges current supplementation strategies that often address single nutrients rather than considering synergistic relationships between vitamins. While folate supplementation is already standard prenatal care, these results suggest B12 status may be equally critical, particularly in populations with limited animal protein intake. The protective iron finding warrants cautious interpretation, possibly reflecting complex metabolic interactions or confounding factors. As a preprint awaiting peer review, these results require validation through additional studies. The work represents an important step toward personalized maternal nutrition approaches, potentially informing more sophisticated supplementation protocols that consider individual micronutrient profiles rather than one-size-fits-all recommendations.