ClinicSpeak: vitamin D supplementation during pregnancy

Are you planning to fall pregnant? Have you had advice about vitamin D? #ClinicSpeak #MSBlog #MSResearch

“This small study from Iran shows that supplementing pregnant women with 50,000 IU/week of vD3 significantly raised levels compared to standard of care. Is this important? Yes, very important. In Iran there is an epidemic of MS that appears to be partly driven by a deficiency of vD (covering up, make-up, pollution, etc). The ratio of females to males with MS in Iran is 5:1; to the best of my knowledge the highest MS sex ratio in the world. Epidemiological studies suggest that some risk of autoimmunity is driven by imprinting in utero on the developing immune system. We think the process is due to epigenetic factors; in other words the environment in the womb alters the way the genome functions and this puts you at risk of developing MS and other autoimmune diseases later in life. Low vD levels in the womb may affect how the immune system develops; we think the thymus malfunctions and does not educate the developing immune system properly. This is why we recommend that all female MSers try and keep themselves vD replete during pregnancy. To do this you probably need ~10,000U vD3 per day. Please note this recommendation is based on a scientific rationale and not a clinical studies. We have yet to start a vD prevention study to prove the hypothesis that vD supplementation in utero and in life reduces the incidence of MS and other autoimmune diseases.”

Etemadifar & Janghorbani. Efficacy of high-dose vitamin D3 supplementation in vitamin D deficient pregnant women with multiple sclerosis: Preliminary findings of a randomized-controlled trial. Iran J Neurol. 2015 ;14(2):67-73

BACKGROUND: The aim of this preliminary study was to assess the safety and efficacy of high-dose oral vitamin D3 supplementation during pregnancy in women with MS in Isfahan, Iran.

METHODS: In a single center open-label randomized, controlled clinical Phase I/II pilot study, 15 pregnant women with confirmed MS with low serum 25-hydroxyvitamin D (25(OH)D) levels were randomly allocated to receive either 50,000 IU/week vitamin D3 or routine care from 12 to 16 weeks of gestation till delivery. The main outcome measures were mean change in serum 25(OH)D levels, expanded disability status scale (EDSS) score, and number of relapse events during pregnancy and within 6 months after delivery.

RESULTS: Average serum 25(OH)D level at the end of trial in vitamin D3 supplemented group was higher than routine care group (33.7 ng/mL vs. 14.6 ng/ml, P < 0.050). In vitamin D3 group, the mean EDSS did not changed 6 months after delivery (P > 0.050), whereas in routine care group, the mean EDSS increased from 1.3 (0.4) to 1.7 (0.6) (P < 0.070). Women in vitamin D3 group appeared to have fewer relapse events during pregnancy and within 6 months after delivery. No significant adverse events occurred.

CONCLUSION: Adding high dose vitamin D3 supplementation during pregnancy to routine care of women with MS had significant effect on the serum 25(OH)D levels, EDSS and number of relapse events during pregnancy and within 6 months after delivery.

About the author

Prof G

Professor of Neurology, Barts & The London. MS & Preventive Neurology thinker, blogger, runner, vegetable gardener, husband, father, cook and wine & food lover.


  • That's really interesting. I'm planning to try for another baby after my second alemtuzumab infusion and presumed I should stop all supplements apart from NICE recommended ones. I'll carry on with my vit d and sunshine having read this. Thanks

  • Before I got pregnant 22 years ago I drove around from one MS specialist in pregnancy to another (pre-Internet days) and no one said a word about Vitamin D. I am thrilled this is now a recommendation for those trying to get pregnant today. Thank you for this important article.

  • Hey.
    I'm interested in your hypothesis above that you think low Vit D causes the Thymus to malfunction and this impacts the education of the newly forming immune cells.

    If this is the case, is it not pretty easy to test in those who've had an induction therapy (Lemtrada, HSCT), to see if Vit D influences the education of what is, similarly, a newly forming immune system post induction?

    Would be a lot quicker, presumably, than testing Vit D on pregnancy as you'd not have to wait 30 to 40 years to see if MS redevelops, and the sample size could be much smaller as you'd already know they were susceptible to MS genetically.

    Has/is this being tested?

    Can't imagine it would be that hard/cost that much. Vit D is dirt cheap. Post induction therapy patients are already followed up regularly for years. So the only effort would be to set up a simple register?


    • It may not be a malfunction, the genes related to MS may have evolved to conserve vitamin d by reducing immune system use, so as to reduce rickets. Trading a short term advantage for a long term disadvantage, you are still alive to breed but you die sooner. The system then may be partially responsive to vitamin d levels before birth. If this is true once the immune system use is down-regulated much higher levels of vitamin d may be needed to turn it back on.

  • What level of vitamin D do you think we should be aiming for (if not pregnant)?

    Mine is now at 120ng/ml (I've been supplementing with 5000IU a day for 5 years) and my GP is a little concerned this is too high, and I should reduce my dose.


    • I hope a doc responds to this as I too would be interested to know.

      Here is the advice from the Vitamin D Council.
      100 -150 ng/ml
      Although these levels aren’t toxic and aren’t usually harmful, they are thought to be too high. There are no known benefits to having a vitamin D level over 100 ng/ml.
      A study by a group of researchers in Utah found that levels over 100 ng/ml are linked to a slight increased risk of developing an irregular heart beat called atrial fibrillation.
      You should take steps to lower your levels to below 100 ng/ml , unless you are under the supervision of your doctor.

      Level greater than 150ng/ml these are toxic levels.

      If you have had your vitamin D levels tested, it’s important to understand what the results mean, and what action you might need to take. The blood test that measures vitamin D is called a 25(OH)D blood test. The results of the blood test can tell you whether you’re getting too little, too much or the right amount of vitamin D. This will help you to decide whether to take more or less supplement, or expose your skin to the sun more.

      When you get your test results you will see a number in units of ng/ml, for example, 50 ng/ml. These are the units that health professionals in the United States use. Elsewhere in the world, vitamin D blood test results are given in units of nmol/l.

      To convert a test result measured in ng/ml to one measured in nmol/l, multiply the ng/ml number by 2.5. For example, 20 ng/ml is the same as 50 nmol/l (20 x 2.5).
      To convert a test result measured in nmol/l to one measured in ng/ml, divide the nmol/l number by 2.5. For example, 50 nmol/l is the same as 20 ng/ml (50÷2.5).

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