Under the national nutrivigilance scheme, five cases of neonatal hypercalcaemia and two cases of congenital hypothyroidism, all sufficiently documented and likely to be related to the consumption of food supplements for pregnant women, were brought to ANSES's attention. These reports of adverse effects led the Agency to assess the endocrine and metabolic risks associated with the intake of vitamin D and iodine through food supplements for pregnant women.
Neonatal hypercalcaemia and vitamin D
The analysis of the reports received showed that the doses of vitamin D provided by "pregnancy" food supplements are not by themselves likely to lead to hypercalcaemia in a pregnant woman or a healthy foetus.
Nevertheless, a genetic hypersensitivity to vitamin D can lead to hypercalcaemia. In the cases reported to the nutrivigilance scheme, screening for a mutation of the gene predisposing to vitamin D hypersensitivity, which is rarely carried out at the moment, would therefore have been able to confirm the origin of the hypercalcaemia observed.
Congenital hypothyroidism and iodine
An adequate iodine status is necessary for the normal neurological and behavioural development of the newborn. On the other hand, an excessive iodine intake (oral or transdermal) during pregnancy increases the risk of hypothyroidism, hyperthyroidism or goitre in the newborn.
For the two sufficiently documented cases of congenital hypothyroidism received by the nutrivigilance scheme, the available data cannot be used to formally incriminate the food supplement, which was not the only source of iodine to which the person was exposed.
The Agency’s recommendations
Besides the cases of vitamin D and iodine, which were specifically the subject of nutrivigilance reports, the Agency warns against combining multiple sources of vitamins and minerals, in the absence of an identified need. Indeed, in some cases this may lead to the safety limits being exceeded. ANSES is issuing the following recommendations:
For pregnant women:
ANSES reminds pregnant women that they should not consume food supplements without first seeking the advice of a healthcare professional, and recommends that they inform their doctor, pharmacist or midwife of any product (drug or food supplement) they have taken, whether it was issued on prescription or purchased over the counter.
For healthcare professionals:
the consequences of hypercalcaemia on newborn health, in the event of hypersensitivity to vitamin D, require appropriate preventive measures to be implemented. In the event of confirmed hypercalcaemia, it will be necessary to search for the cause with the appropriate examinations and reconsider the relevance of vitamin D supplementation for the pregnant woman ;
in newborns, an unexplained hypercalcaemia could be related to a genetic hypersensitivity to vitamin D. In cases of unexplained hypercalcaemia, therefore, it is important to screen for a possible mutation of the gene predisposing the child to hypercalcaemia and to take the appropriate measures ;
the simultaneous exposure to multiple sources of iodine (from drugs or food supplements) increases the risk of thyroid disorders in newborns and must therefore be avoided during pregnancy ;
the Agency stresses the importance of not combining different sources of vitamins and minerals without regular biological monitoring.
Lastly, the Agency reminds healthcare professionals of the importance of notifying the nutrivigilance scheme of any adverse effects they are made aware of, which could be related to the consumption of food supplements.