Maternal vitamin B12 deficiency detected in expanded newborn screening

• Newborn screening evidences the high frequency of acquired vitamin B12 deficiency.
• Monitoring of B12 and Holo-TC from pregnancy to delivery should be introduced.
• Current vitamin B12 reference interval does not prevent false negative cases.
• Newborns from mothers with low B12 should be tested for B12, Holo-TC, MMA, and Hcy.
• It is suggested to supplement all mothers with B12 during pregnancy and lactation.

ObjectivesBesides the inherited form, vitamin B12 deficiency may be due to diet restrictions or abnormal absorption. The spread of newborn screening programs worldwide has pointed out that non-inherited conditions are mainly secondary to a maternal deficiency. The aim of our work was to study seven cases of acquired vitamin B12 deficiency detected during our newborn screening project. Moreover, we aimed to evaluate vitamin B12 and related biochemical parameters status on delivering female to verify the consequences on newborns of eventually altered parameters.Design and methods35,000 newborns were screened; those showing altered propionyl carnitine (C3) underwent second-tier test for methylmalonic acid (MMA) on dried blood spot (DBS). Subsequently, newborns positive to the presence of MMA on DBS and their respective mothers underwent further tests: serum vitamin B12, holo-transcobalamin (Holo-TC), folate and homocysteine; newborns were also tested for urinary MMA content. A control study was conducted on 203 females that were tested for the same parameters when admitted to hospital for delivery.ResultsApproximately 10% of the examined newborns showed altered C3. Among these, seven cases of acquired vitamin B12 deficiency were identified (70% of the MMA-positive cases). Moreover, our data show a high frequency of vitamin B12 deficiency in delivering female (approximately 48% of examined pregnants).ConclusionsWe suggest to monitor vitamin B12 and Holo-TC until delivery and to reconsider the reference interval of vitamin B12 for a better identification of cases at risk. Finally, newborns from mothers with low or borderline levels of vitamin B12 should undergo second-tier test for MMA; in the presence of MMA they should be supplemented with vitamin B12 to prevent adverse effects related to vitamin B12 deficiency.