Introduction
Material and methods
Results
What determines serum folate concentration?
Importance of folate in pregnancy
Folate and antiseizure medication
Adverse effects of excess folic acid
Folic acid dose
Guideline or recommendation | Year of publication | Dose recommendations |
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International League Against Epilepsy [61] | 2019 | At least 0.4 mg daily, and 4–5 mg depending on antiseizure medication, not specified. A continuous dose of 0.4 mg daily is recommended for everyone of childbearing potential during all fertile years |
The National Institute for Health and Care Excellence, The United Kingdom [6] | 2022 | Folic acid is recommended before and during pregnancy; dose and length of treatment in days not specified |
The German Neurological association | 2017 | 5 mg daily in persons using valproate; length of treatment in days and dose for persons using other antiseizure medication not specified |
The American College of Obstetricians and Gynecologists [62] | 2017 | 4 mg daily before and during pregnancy for persons at risk; 0.4 mg daily for persons treated with antiseizure medication |
American Academy of Neurology [63] | 2009 | At least 0.4 mg before and during pregnancy |
Society of Obstetricians and Gynaecologists of Canada [15] | 2022 | 1 mg daily before and during first trimester, 0.4 mg daily thereafter. Serum folate > 28–30 nmol/L or red blood cell folate > 907 nmol/L |
UpToDate [64] | 2022 | 4 mg daily for persons treated with carbamazepine or valproate; 1 mg if treated with other types of antiseizure medication |
Scottish Intercollegiate Guidelines Network [5] | 2015 | 5 mg daily before and during pregnancy for all types of antiseizure medication |
Danish Health Authority [7] | 2005 | At least 0.4 mg daily; 5 mg daily if treated with older types of antiseizure medication, not specified |
Current Care Guidelines, Finland [65] | 2020 | Similar to the general population: 0.4 daily and 4 mg daily if family history of a child with neural tube defect |
The National University Hospital of Iceland [66] | 2019 | 5 mg daily during first 3 months of pregnancy for all types of antiseizure medication. Discontinuation initiated by a clinician |
The Norwegian National Centre for Epilepsy [9] | 2022 | 4 mg daily to persons treated with valproate or with antiseizure medication for which fetotoxicity is not fully known, immediately before and during first 3 months of pregnancy, thereafter 0.4 mg daily |
The Norwegian Medical Association [67] | 2018 | 4–5 mg from contraception is discontinued until 2nd trimester, thereafter 0.4 mg. A continuous dose of 0.4 mg daily is recommended for everyone of childbearing potential during all fertile years |
Swedish Medical Products Agency [8] | 2019 | 0.4 mg daily to all before and during pregnancy independent of concomitant antiseizure medication |
Discussion
Practical conclusion
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Folate is most likely important for the outcome in children of mothers on antiseizure medication (ASM). Folate status should be optimized before conception and throughout pregnancy.
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The optimal dose of ASM is unknown, but recent guidelines recommend doses of 0.4–4 mg daily before pregnancy and at least during the first 12 gestational weeks. As the safety of excess folic acid is questioned, supplementation higher than needed should be avoided. In pregnant people without epilepsy, the optimal serum folate concentration is > 28–30 nmol/L or red blood cell concentration > 906 nmol/L. Folic acid dose titration according to the folate concentration is a possible strategy in pregnancy management of persons with ASM-treated epilepsy.
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Folic acid supplements could mask vitamin B12 deficiency, which should also be measured before starting folic acid supplementation.
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Future studies should focus on the efficacy and safety of individualizing folic acid dose according to concentration measurements.