Vitamin B12 Deficiency in Pregnancy Worse Than Thought: New Study
Oleh 22 Desember 2017

Vitamin B12 Deficiency in Pregnancy Worse Than Thought: New Study

Babies will face the problematic or delayed diagnosis when pregnant women experience symptoms of vitamin B12 deficiency, study has shown.

Almost half of all pregnant women are deficient in vitamin B12 leaving their babies exposed to potential developmental problems, according to a recent study published in the journal Clinical Biochemistry.

Symptoms of vitamin B12 deficiency in neonates may include developmental delay, failure to thrive and similar non-specific symptoms that may result in problematic or delayed diagnosis.

The study of vitamin B12 levels in 35,000 babies reveals that 0.02% of neonates and 48% of pregnant women are deficient in this esseDential vitamin which is vital in metabolism and DNA synthesis and important for brain and nervous system function.

The data showed that approximately 10% of the newborns examined had altered propionyl carnitine concentrations (C3), a marker of vitamin B12 deficiency and 7 cases of vitamin B12 deficiency were identified. (1)

“In this study we report 7 cases of acquired vitamin B12 deficiency, due to a maternal defect, in 35,000 live births (0.02%),” reported Dr Emanuela Scolamiero of the Biotecnologie Avanzate, Italy.

To assess the extent of maternal vitamin B12 deficiency, the researchers also investigated serum vitamin B12, holo-transcobalamin, folate and homocysteine levels in a cohort of 203 women admitted to hospital for delivery.

Due to extensive folate supplementation in the cohort, folate and homocysteine levels were normal, however mean vitamin B12 levels were 202 pmol/L with 48% of women having concentrations in the deficient range (defined as <138 pmol/L for this study).
The authors emphasised that vitamin B12 deficiency is common, with a high incidence even in industrialised countries, and that most neonatal deficiency is secondary to maternal deficiency.

In the body, vitamin B12 (also known as cobalamin) is transformed to three activated forms – cobalamin I, II and III.  These active forms of cobalamin are vital co-factors for two crucial metabolic enzymes: methylmalonyl-CoA mutase and methionine synthase. Vitamin B12 deficiency therefore has a direct impact on DNA synthesis, red blood cell production and the development of the central nervous system.

The most sensitive markers of vitamin B12 deficiency are increased blood concentrations of methylmalonic acid (MMA) and propionyl carnitine (C3) as these are the substrates of the enzymes requiring cobalamin as co-factor.

Dr Scolamiero concluded that: “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”.

A second, earlier study showed that maternal vitamin B12 deficiency was common in mothers of babies with neural tube defects. (2)  Dr Anne Molloy and colleagues conducted the research at Trinity College Dublin School of Medicine and the findings were published in the journal Pediatrics. (2)

“We have shown, in 3 separate groups, that low B12 status is an independent maternal risk factor for having a neural tube defect affected pregnancy,” reported Dr Molloy.

“Our data indicate that women with pregnancy B12 concentrations of <200 ng/L are at 3 times greater risk than those with levels of >400 ng/L”.

The three groups consisted of women during a neural tube defect–affected pregnancy (n=95) and appropriate controls (n=265), women who had a previous neural tube defect birth but whose current pregnancy was not affected (n=107) and controls (n=414) and a historical group of biobank samples from women during an affected pregnancy (n=76) and controls (n=222).

Vitamin B12 deficiency is a particular problem for people adhering to a vegetarian or vegan diet as vitamin B12 cannot by synthesised in the body and must be obtained from meat, dairy and egg products.  Research has shown that 52% of vegans, 7% of vegetarians and 0.4% of omnivores are vitamin B12 deficient. (3)

There are a number of medications that may reduce vitamin B12 levels (4), including the gout medication Colchicine, anti-seizure medications such as phenytoin, phenobarbital and primidone and bile acid sequestrants such as colestipol, cholestyramine and colsevelam. Metformin, H2 inhibitors and proton pump inhibitors have also been shown to significantly reduce B12 levels.

Vitamin B12, along with all other B vitamins, should be also taken at a different time from tetracycline as it alters the absorption and effectiveness of this antibiotic.

Of note, the definition of vitamin B12 deficiency varies from <130 pmol/L to <258 pmol/L for different countries, further complicating diagnosis of this condition.

1. Scolamiero et al. Maternal vitamin B12 deficiency detected in expanded newborn screening. Clin Biochem. 2014 Sep 7. pii: S0009-9120(14)00655-9. doi:10.1016/j.clinbiochem.2014.08.020. [Epub ahead of print]

2. Molloy et al. Maternal vitamin B12 status and risk of neural tube defects in a population with high neural tube defect prevalence and no folic acid fortification. Pediatrics 2009;123:917–23.

3. Zeuschner et al.  Vitamin B12 and vegetarian diets. MJA Open 2012; 1 Suppl 2: 27-32.

4. Vitamin B12 (cobalamin) | University of Maryland Medical Center 


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