Pregnant women increase their chances of vitamin B12
deficiency if they don’t consume enough meat, milk
or eggs. This vitamin is found only in animal
products. A deficiency of the vitamin during
pregnancy could have dramatic consequences for the
In an in-depth study of 11,216 pregnancies from 11
countries, researchers have concluded that low
levels of vitamin B12 are associated with an
increased risk of preterm birth.
Globally, low birth weight and preterm births cause
half of all infant deaths in the first 28 days after
birth. The diet of a pregnant woman is vitally
important for her foetus and pregnancy.
“Vitamin B12 is an essential nutrient found only in
products of animal origin such as meat, milk and
eggs. Pregnant women who consume too few
animal-derived foods increase their risk of
developing a vitamin B12 deficiency,” says Tormod
Rogne, a medical doctor and intern at Akershus
University Hospital near Oslo. The study is part of
his doctoral thesis at NTNU’s Department of Public
Health and Nursing, completed in December 2016.
Vitamin B12 is necessary for the body’s vital
functions, including the production of red blood
cells and cellular metabolic energy. B12 deficiency
can cause anaemia and severe damage to the nervous
system. The body cannot produce the vitamin itself.
In countries where people eat high levels of animal
products, such as Norway and numerous Western
countries, only a small percentage of pregnant women
have a vitamin B12 deficiency.
“In countries where vegetarian diets predominate,
such as in India, the percentage of pregnant women
with B12 deficiency can exceed two thirds,” Rogne
The analysis included 94 per cent of all pregnancies
that were part of any published study on B12 levels.
“Low levels of vitamin B12 in pregnant women did not
appear to affect the newborn’s birth weight. But we
did find that vitamin B12 deficiency during
pregnancy was associated with a 21 per cent
increased risk of giving birth prematurely,” said
The results were independent of whether the
countries had high, middle or low average incomes.
Rogne stresses that it is important to remember that
there may be other reasons for the apparent link
between vitamin B12 deficiency and preterm births.
“Low blood concentrations of vitamin B12 may be
related to other factors, such as malnutrition and
poverty, which can also affect birth weight and
length of pregnancy,” he said.
"The importance of B12 is widely known and not
contested by those of us who work with veganism and
vegetarian. We are very keen to spread knowledge
about B12, especially to vegans who do not eat meat,
dairy products or eggs," says information officer
Paul W. Thorbjörnsen from the Norwegian Vegetarian
"B12 is not a big problem for vegetarians because
they eat dairy products and eggs. We advise vegans
to consume B12 by drinking products such as soy milk
or rice milk with added B12, or that they take
”Although we found that vitamin B12 deficiency is
associated with an increased risk of preterm birth,
we know very little about the effects of taking
vitamin B12 supplements during pregnancy.”
Rogne said he knew of only two small studies, for
which pregnant women were randomly selected to take
either vitamin B12 or a placebo during pregnancy.
These studies found no definitive link between
vitamin B12 supplementation and birth weight. This
is consistent with the findings from Rogne’s study.
However, there were too few participants in the two
studies to conclude whether B12 supplementation
during pregnancy may reduce the risk of preterm
“Before we can say anything about the effect of
vitamin B12 supplementation in pregnancy, more of
these kinds of studies need to be done, and the
results should then be summarized in a review
article. We hope that our article will encourage
people to undertake these studies so that we can
provide solid advice for pregnant women who don’t
eat much in the way of animal-derived foods,” said
According to Videm, a professor in NTNU’s Department
of Laboratory Medicine, Children’s and Women’s
Health, also author of the Norwegian book Verdt å
vite om vegetarmat (Good to know about vegetarian
food), a combination of 3 dl milk and 50-75 grams of
cheese (5-8 slices) will do it outside of pregnancy.
If you want, you can substitute 80 g (4 tablespoons)
cottage cheese for the cheese.
Pregnant women, she says, need a bit more: adding
either a glass of milk, a good portion of yogurt or
3-4 extra slices of cheese will provide what is
needed by a good margin.
For more information
Published in the 20 January 2017 issue of the
American Journal of Epidemiology
Associations of Maternal Vitamin B12 Concentration
in Pregnancy With the Risks of Preterm Birth and Low
Birth Weight: A Systematic Review and Meta-Analysis
of Individual Participant Data