ABSTRACT
BACKGROUND: Vitamin B12 deficiency during pregnancy and lactation may negatively affect fetal growth, brain development, pregnancy outcome, and breastmilk vitamin B12 content. OBJECTIVE: To examine associations between pregnant and lactating women's vitamin B12 intake and pregnancy outcomes, breastmilk vitamin B12 concentration, and growth and development of breastfed infants from birth to 6 months. METHODS: One hundred thirty-eight Kenyan women were followed during pregnancy, with 98 followed through 6 months of lactation and providing 294 randomly collected breastmilk samples. Maternal hematologic analyses were performed for erythrocyte morphology, erythrocyte size, and serum vitamin B12 concentration. Women's and infants'food intake was assessed. Breastmilk vitamin B12 was measured by a competitive binding isotope dilution technique. Infant anthropometric data and the Brazelton Neonatal Behavioral Assessment Scale (BNBAS) were assessed within 3 days after birth. The Infant Bayley Motor Scale was assessed at 6 months. Statistical analyses included simple regression and correlation analyses in relation to vitamin B12 status and gestational age. RESULTS: Intrauterine growth restriction and stillbirths were correlated with maternal macrocytic anemia and hypersegmented polymorphonuclear nuclei. Postpartum maternal vitamin B12 intake influenced breastmilk vitamin B12 levels 1 to 6 months postpartum. No associations were found between vitamin B12 intake during pregnancy or vitamin B12 levels in breastmilk and infant length, weight, or head circumference at birth or 6 months. Vitamin B12 intake during pregnancy was correlated with improved scores on infants' BNBAS reflex subscale (R = -0.19, p = .05) with adjustment for gestational age. Bayley Motor Scale results at 6 months were not significantly associated with breastmilk or supplemental feeding vitamin B12 content. CONCLUSIONS: Vitamin B12 deficiency may adversely affect pregnancy outcome, infant reflexes at birth, and breastmilk vitamin B12 content.