Maternal First-Trimester Vitamin B12 Levels as a Determinant of Infant Deficiency: A Single-Center Retrospective Study.

Background Vitamin B12 deficiency in infancy may lead to growth retardation, anemia, and neurodevelopmental delay. Therefore, identifying maternal predictors is essential for early prevention. The significance of vitamin B12, particularly during pregnancy and early infancy, has been acknowledged. This study aims to identify the etiological factors in infants aged 9-12 months diagnosed with vitamin B12 deficiency. Methodology This study aimed to retrospectively evaluate the characteristics of infants aged 9-12 months with vitamin B12 levels ≤300 pg/mL and investigate the maternal vitamin B12 status during the first trimester. Results This retrospective study included 217 breastfed infants with vitamin B12 levels ≤300 pg/mL and a median age of 9.93 (9.0-12.0) months. Their median vitamin B12 level was 212 (100-300) pg/mL, with 43.8% (n = 95) having levels below 200 pg/mL, and 56.2% (n = 122) between 200 and 300 pg/mL. The median hemoglobin level was 11 g/dL, with anemia (<10.5 g/dL) present in 29% (n = 63) of infants; however, no cases of macrocytic anemia were observed. The first-trimester median vitamin B12 level in mothers was 246 (120-397) pg/mL, with 26% (n = 57) below 200 pg/mL, 50% (n = 109) between 200 and 300 pg/mL, and 23% (n = 51) above 300 pg/mL. Logistic regression analysis showed that infants of mothers with B12 <200 pg/mL had a 25.76 times higher risk of deficiency compared to the reference group (mothers with B12 >300 pg/mL) (relative risk = 25.760, 95% confidence interval = 8.616-77.013, p < 0.001). Among mothers, 62.6% with low B12 (<200 pg/mL) received treatment, predominantly with oral cyanocobalamin combinations, and the mean treatment duration was one month (n = 86, 94.5%). Conclusions Vitamin B12 deficiency is a common and underestimated public health problem in developing countries. This study demonstrates that maternal first-trimester vitamin B12 levels are the strongest determinant of deficiency in breastfed infants aged 9-12 months. These findings underscore the clinical importance of assessing maternal B12 status during pregnancy and even before conception as a primary preventive strategy.