Adequate vitamin status in utero is essential for healthy fetal development and optimal adult health and wellbeing(Reference Elmadfa and Meyer1). During pregnancy, vitamin B12 requirements increase(2) due to rapid cell division, placental development and fetal growth(Reference Samuel, Duggan and Thomas3). Low maternal vitamin B12 status has been identified as an independent risk factor for neural tube defects(Reference Molloy, Kirke and Troendle4), the incidence of which is increasing in Ireland(Reference McDonnell, Delany and O'Mahony5). Inadequate maternal vitamin B12 status has also been associated with other adverse pregnancy outcomes including preterm birth(Reference Murphy, Molloy and Ueland6), small for gestational age(Reference Samuel, Duggan and Thomas3), and cognitive impairment in infants(Reference Black7). The Irish RDA for vitamin B12 for women in the first trimester of pregnancy is 1·4μ g/d(8). The Institute of Medicine (IoM) RDA for pregnancy is 2·6 μg/d(2).
This observational study examined maternal vitamin B12 intakes in the first trimester.
Women were recruited at their convenience after sonographic confirmation of a singleton pregnancy in the first trimester. Maternal body composition was measured using 8-electrode bioelectrical impedance analysis, and dietary data collected using an interviewer-assisted 4-day retrospective food diary (FD) in combination with a food frequency questionnaire (FFQ); an approach previously validated against biomarker data(Reference Molloy, Kirke and Troendle4). All reported portion sizes were fully quantified using food portion size estimation tools. Nutrient analysis was carried out using Nutritics version 3.7 University Edition which included the most up-to-date nutrient composition for fortified foods.
Of the 481 women recruited, the mean BMI was 26·0 kg/m2 (±5·5) and 19·2 % were obese. Mean maternal age was 30·6 (± 5·6) years. In total, 41·8 % (201/481) were defined as energy under-reporters and were excluded from further analysis(Reference Black9). Among plausible reporters, the mean (SD) vitamin B12 intake was 5·1μ g/d (±2·2). Overall, 97·9 % (274/280) met the Irish RDA of 1·4 μg/d8, and 99·6 % (279/280) met the Irish EAR of 1·0μg/d(8). In comparison, 91·8 % (257/280) met the IoM RDA of 2·6 μg/d for pregnancy(2).
This study suggests that most pregnant women in Ireland are achieving the current Irish EAR & RDA for vitamin B12. However, the 8·2 % failing to achieve the higher IoM target of 2·6 μg/d(2) does present some cause for concern.
