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B12 and pregnancy

In an ideal world all doctors would thoroughly test pregnant women or those trying to conceive for B12 deficiency. If you've had trouble conceiving, or lost pregnancies through miscarriage, you should have your vitamin B12 levels checked please see

Please see the What to do next page if you think you may be affected by B12 deficiency. We have also developed an app to help determine your risk of B12 deficiency.

If you feel you need personalised help please see the contact page for more information.


Up to date education of B12 deficiency is limited and it may be that your nurse/midwife may never have been taught the importance of B12 deficiency. Many only learn about it when they themselves are diagnosed. There are many causes of this condition, please take a look here for more information.

New research shows that; Women who begin pregnancy with depleted stores (low or very low plasma cobalamin) will give birth to depleted infants who are likely to develop deficiency symptoms during the first few weeks or months postpartum.

The demands of pregnancy on B12 deficient patient are huge but sadly many doctors incorrectly believe B12 injections are unsafe in pregnancy when the opposite is in fact true. B12 deficiency must be treated in a pregnancy, it is as important as folate or iron deficiency.

Some manufacturers of hydroxocobalamin state that you should ask your doctor or nurse for advice before being given B12 injections. This causes worry and confusion for a mother and a reluctance to treat in a doctor lacking correct knowledge of the condition.

It may be that you, like me, cannot tolerate folic acid and need an active form of folate (vitamin B9). 

Please make sure that your doctor understands that continuing treatment for B12 deficiency must continue throughout pregnancy. B12 is non toxic and cannot be overdosed.

If you need help in accessing treatment and you are in the UK perhaps this link will help.

Folate supplementation prior to conception could mask a potential deficiency.  Health professionals need to be aware of this fact in order to save many couples facing potentially expensive, unnecessary treatments or remaining childless. Low B12 also has links to post natal depression and pre eclampsia.

Click here to read about Inborn errors of B12 metabolism.

Information below supplied with kind permission of Sally M. Pacholok R.N. and Dr. Jeffrey J. Stuart.

Pregnancy represents a huge challenge for those who have an undiagnosed B12 deficiency, the growing baby will take all the B12 supplies it needs leaving the mother desperately short.
In addition, the use of nitrous oxide during labour can completely inactivate any remaining supply of B12. Pregnant women at greatest risk for deficiency include vegans and vegetarians, those with autoimmune pernicious anaemia or malabsorption syndromes such as Crohn's disease or coeliac disease. Those with a history of gastric bypass for weight loss, strict dieting, anorexia, or bulimia.

B12 deficiency and Miscarriage: Far More Common Than Doctors Think

A recurring theme in medical literature is that B12 deficiency is a fairly rare cause of miscarriage or stillbirth. The evidence, however, suggests otherwise. One recent study, for instance, compared thirty-six women who'd suffered recurrent foetal loss to forty women who'd carried healthy babies to term. The researchers found that 31 percent of the women who'd lost several babies had high homocysteine levels. (Elevated homocysteine is caused by low levels of folate, B12 and/or vitamin B6, and is easily treated with these vitamins).

Sixteen percent of the women who'd suffered recurrent foetal loss carried two copies of the MTHFR gene that causes abnormally high homocysteine levels, and three of the women had overt B12 deficiency.

Click here to read more.

B12 deficiency and Neural Tube Defects

When mothers are deficient in B12 the damage to their babies starts in the womb. You've probably heard of neural tube defects (NTDs), which are very common, severe birth defects occurring when the brain or spinal cord fails to form correctly. Low levels of folic acid increase the risk for NTDs which is why doctors now ensure that their pregnant patients get plenty of this vitamin. However, research strongly implicates low B12 levels as a factor in NTDs, which isn't surprising, since folic acid and B12 work hand in hand.

Tests that could save a mother's sanity and a child's life

More research is needed to determine the incidence of B12 deficiency in women with post natal depression or post natal psychosis. In the meantime, we believe that all women diagnosed with post natal mental illness should undergo screening, including serum B12 and urinary MMA tests. Pregnancy can dramatically worsen a pre-existing B12 deficiency, because B12 is transferred to the growing foetus throughout pregnancy, and prenatal vitamins contain only six micrograms of this nutrient (compared to the 1,000 micrograms needed to treat deficiency). Pregnant women at greatest risk for deficiency include vegans and vegetarians, those with autoimmune pernicious anaemia or malabsorption syndromes such as Crohn's disease (an inflammatory intestinal disease) or coeliac disease, and those with a history of gastric bypass for weight loss, strict dieting, anorexia, or bulimia. However, any women who develops symptoms of mental illness following pregnancy needs B12 screening.

Mothers with depleted B12 stores...

who exclusively breast feed their babies unknowingly put them at great risk for developmental disability or even death. This is a common cause of B12 problems in infants; one study for instance, found that a group of six infants became ill after being nursed by vegetarian mothers.  (The other half were born to mothers with undiagnosed pernicious anaemia).

Vegetarian and vegan mothers are devastated and feel tremendous guilt when their children suffer harm due to B12 deficiency, but in reality, most of these tragedies are the fault of doctors who fail to screen pregnant and nursing mothers for this deficiency - and who then often misdiagnose these women's children as intellectually disabled or autistic, rather than considering B12 deficiency when the infants lose their speech, social skills and motor skills.

Please note, there are many causes of B12 deficiency click here for more information. 

Click here to read relevant medical journals

Please click here to read about B12 and male and female infertility.

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