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.