Pourquoi faut-il éviter la carence en vitamine B12 durant la grossesse ?

Why should vitamin B12 deficiency during pregnancy be avoided?

In pregnant women, the fundamental role of vitamin B12 for the harmonious development of the fetus and in particular of its nervous system is better documented and recognized.
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In pregnant women, the fundamental role of vitamin B12 for the harmonious development of the fetus and in particular of its nervous system is increasingly better documented and recognized. This is why it is important, when talking about vitamin B12, to avoid deficiencies.

In December 2020, a landmark study was published in the English journal Nutrition Research to highlight the relationship between the level of vitamin B12 in pregnant women during pregnancy and its consequences on the cognitive abilities of children, for several years afterwards.

This is the first time in the world that such work associating the vitamin B12 levels of mothers with the cognitive abilities of their children has been carried out, over such a long period, with such a large cohort (12,000 women and their children).

The conclusions are presented below, but demonstrate the non-reversible nature of vitamin B12 deficiencies during pregnancy on certain mental abilities of children.

In this article we will therefore return to the role of vitamin B12 in pregnant women, the risks of deficiencies for the future baby as well as the means available to have sufficient intake.

The role of vitamin B12 in the development of the future child

Vitamin B12 is involved in the metabolism of every cell in the human body, at all ages.

It is involved in particular in:

  • Deoxyribonucleic acid (DNA) methylation
  • Myelination of neurons
  • The metabolism of fatty acids and amino acids

The importance of vitamin B12 in neurodevelopment is supported by case studies of deficient infants with brain atrophy and demyelination of nerve cells.

After treatment with vitamin B12, rapid improvement in neurological symptoms was reported, but many infants remained significantly delayed in the development of cognition and language.

Therefore, expectant mothers should avoid vitamin B12 deficiency because this vitamin is particularly important for the normal functioning of the nervous system and plays an important role in the growth and development of the fetal brain.

The consequences of vitamin B12 deficiency during pregnancy

We took the results of the study mentioned previously and published in December 2020 in the English journal Nutrition Research.

The rigorous scientific work of Jean Golding's team is based on the cross-checking of data from 12,000 pregnant women * and the children born from them over a period of more than 10 years.

This study is fundamental because of the objective results it demonstrates:
More than 10 years after birth, some children affected by vitamin B12 deficiencies during pregnancy retain some lower cognitive abilities .

They show that children born to mothers whose vitamin B12 intake was the lowest (10%) had an increased risk of having:

  • Insufficient vocabulary at 24 months
  • Reduced ability to combine words at 38 months
  • Poor speech intelligibility at 6 years old
  • Poor understanding of mathematics between ages 8-9 and 10-11
  • Poor results in national mathematics tests (13 years old).

However, fortunately, the study also shows that there are no such significant associations between vitamin B12 deficiency and reading or spelling skills, nor for verbal or complete IQ (intelligence quotient). at 8 or 15 years old.

Thus, the study establishes that the negative effects of a lack of vitamin B12 in the mother on the child's development are specific to certain language and mathematics abilities.

* from the 'ALSPAC' longitudinal parent and child survey. The results were processed and analyzed with a statistical methodology making it possible to eliminate as much as possible the sociological effects which interfere with the cognitive abilities of children.

How to prevent vitamin B12 deficiency in pregnant women?

As we have mentioned, the mother-to-be's diet will have a direct influence on the child's development and health.

Also, toprevent vitamin B12 deficiency in children , it is recommended that all pregnant women, regardless of their diet, have their dietary intake of vitamin B12 assessed and follow the recommendations of the health professionals in charge. of their follow-up.

For pregnant women on a vegetarian or vegan diet, vitamin B12 supplementation is a non-disputable obligation.

Vitamin B12 requirements in pregnant women

Pregnancy gradually increases the vitamin and mineral needs of the future mother because it provides the fetus with all the nutritional elements necessary for its growth.

This is why it is recommended that pregnant women increase their vitamin B12 intake by at least 10% compared to “adult” needs.

The RDA (daily intake) dilemma for vitamin B12 in adults:

The official recommendations for vitamin B12 (RDA from ANSES in France, from the European EFSA, from the American authorities) are 2.5 micrograms per day because they take into account dietary intake from meat products.

However, in the absence of vitamin B12 intake from meat products, the daily requirements for adults are estimated at 10 micrograms per day. There is consensus between the different vegan nutrition associations on this point.

In pregnant women, knowing that there is no risk of overdose of vitamin B12 , a prudent recommendation is to have a total daily intake of:

  • 5 micrograms for omnivores
  • 10 micrograms for vegetarian and vegan diets.

Important note: the dose provided by vitamin B12 supplementation can be adjusted depending on the frequency of intake (daily, weekly, etc.).

To learn more about active and passive absorption mechanisms, we invite you to consult our article on this subject .


  • (1) Maternal prenatal vitamin B12 intake is associated with speech development and mathematical abilities in childhood: https://www.sciencedirect.com/science/article/pii/S027153172030587X?via%3Dihub
  • https://www.canada.ca/en/health-canada/services/food-nutrition/healthy-nutrition/nutritional-reference-reference/tables/values-reference-relative-vitamins-tableaux-nutritional-apports-reference- 2005.html
  • https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/

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