Jul 12 2016

Vitamin Supplements in Pregnancy

vitamins pregnancyFor a moment, imagine that you did not read the title of this article. What if I told you that a drug manufacturer was trying to get the public to use more of their drug, arguing it was necessary when the evidence shows that it isn’t? One trick that they use is to conduct studies in developing countries with a sicker population, and then apply that data to the developed world.

Even in the face of a thorough expert review of the published evidence, that concludes that the public is overusing their product and wasting money, the drug company argues that people still need their drug “just in case.”

Of course, in such a case, there would be cries of “Big Pharma” and the company would be rightly criticized for deceptive marketing and pushing their drug despite the published evidence.

For some reason, when the “drug” is a multivitamin, many people have a different reaction.

A recently published systematic review of the evidence by an expert panel concluded that routine multivitamin supplementation was not necessary for pregnant women. There is simply no health benefit to the mother or the child.

They reviewed the evidence for specific vitamins and for multivitamins. They found that two vitamins were necessary for routine supplementation in pregnancy – folic acid and vitamin D.

Folic acid has been shown to reduce the incidence of neural tube defects in newborns. Neural tube defects are a developmental abnormality of the nervous system, and can result in problems such as spina bifida. Folic acid, which you need to take prior to becoming pregnant (once you find out you are pregnant, it is already too late) is a true preventive intervention, reducing the incidence of this serious malformation.

Vitamin D has been shown to improve the bone health of mother and baby. Although the evidence is less clear, it does favor routine supplementation.

There was no evidence to support routine supplementation for other specific vitamins (iron, Vitamins C, E, and A, and multivitamins were studied).

Please note the term “routine” – that means that all women who are pregnant or planning to become pregnant should take folic acid and vitamin D. For the other supplements, you should only take them if a blood test determines that you are insufficient or deficient. That is not routine supplementation (for pregnancy), but targeted supplementation.

What the experts recommend is that pregnant women take folic acid and vitamin D and that they otherwise eat a well-rounded diet with plenty of fruits and vegetables.

At this point, many readers may be wondering, “What’s the harm? Why not take some extra vitamins as nutritional insurance?” That is what the supplement industry wants you to believe. There are several reasons why this can be harmful.

The first is that unnecessary vitamins can be expensive (while the recommended dose of folic acid and vitamin D are relatively inexpensive and in the UK are offered free to pregnant women). For those with a lot of disposable income this is not a big deal, but for many people with limited income this can be an important financial calculation.

Being pregnant and having children are expensive. Guilting women into expensive and unnecessary multivitamins could affect their bottom line and detract from other necessary resources. In fact, they would be better off spending that money on fresh produce.

Secondly, some vitamins, vitamin A in particular, can actually be harmful during pregnancy. High doses of vitamin A can increase the risk of developmental abnormalities.

It is possible to get too much vitamin A during pregnancy just from food, although this risk is low. It is very easy to get too much if you are unnecessarily supplementing. Also keep in mind that there is now a lot of fortification of common foods with vitamins. Many water drinks now contain vitamins, for example.

I routinely check certain vitamin levels in my patients and high levels of certain vitamins (such as B6) are not uncommon, even to the point that they are dangerous. Sometimes the patient is not specifically supplementing that vitamin and they don’t even know where the excess is coming from.

The authors of the study note:

“Many nutritional supplements containing vitamins, minerals and other micronutrients are heavily marketed to women for all stages of pregnancy. However, much of the evidence for vitamin supplementation in pregnancy comes from studies carried out in low-income countries, where women are more likely to be undernourished or malnourished than within the UK population.”

The supplement industry, unsurprisingly, rejects the findings:

But Dr Carrie Ruxton, a dietitian and spokeswoman for trade body the Health Supplements Information Service, rejected the findings.

“The authors of this study claim that vitamin and mineral supplements must produce clinical effects before pregnant women are encouraged to take them. This is absolute nonsense. Except for folic acid, which does have a therapeutic role by actively preventing neural tube disorders, the role of food supplements is simply to combat dietary gaps.”

However, the evidence shows that, for most women, there are no gaps and that if there are gaps, the better advice to give women is to close the gaps with an improved diet, not just to take supplements. This, in fact, is a third source of harm – the false sense of security. Taking vitamins is presented as an easy way to ensure proper nutrition (to close the gaps), but the evidence overwhelmingly shows that it isn’t. You actually need to have a proper diet.

The advice to give routine supplementation also ignores the fact that you can measure specific vitamin levels and give targeted advice to individuals.

Again, imagine if a drug company said it was nonsense that you need to have evidence of a clinical benefit before recommending their drug.


The aforementioned recent review of supplementation in pregnancy mirrors similar reviews for the general population – routine multivitamin supplementation has no proven benefit. In fact, it brings risks of vitamin excess, wasted resources, and justifying a poor diet.

The exceptions for pregnant women are folic acid and vitamin D. The evidence does support routinely taking these vitamins before and during pregnancy.

Of course, the best advice is to have good prenatal care and to follow the tailored advice of your OB.

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