I’m pregnant. Do I need a multivitamin?

Growing a healthy baby relies on getting enough nutrients while pregnant.

But rather than following a healthy diet to provide those nutrients, we’re concerned too many people are relying on “pink” multivitamins.

These supplements are widely promoted for people who are pregnant or breastfeeding, and those who are planning to become pregnant. They contain folic acid, iodine, iron, vitamin D, vitamin B12, calcium, and a shopping list of other vitamins and minerals.

Multivitamins during pregnancy are, for the most part, a waste of money. At worst, there’s a risk they can harm you and your baby.

Most need only folate and iodine

Official dietary advice recommends only two nutrient supplements before and during pregnancy: folic acid (folate) and iodine.

A folic acid supplement is recommended from the month before conception and during the first three months of pregnancy. The recommended dose is 400 micrograms a day to reduce the risk of neural tube defects (such as spina bifida) in the newborn. Requirements for folate remain high for the whole pregnancy, and some people may be prescribed higher folic acid doses or other forms of folate based on their individual medical needs.

Due to mild iodine deficiency in Australia, people who are pregnant, breastfeeding or considering pregnancy should also take an iodine supplement at 150 micrograms a day to support the baby’s brain development. People with thyroid issues should speak to their doctor first.

However, individual circumstances may need someone to take other nutrients while pregnant. For instance, on advice from their health-care provider, people who are vegetarian or vegan may need to take vitamin B12 and iron supplements. People diagnosed with deficiencies such as vitamin D or iron will be prescribed a supplement to build up their levels. Those at risk of certain health conditions, such as pre-eclampsia, may need to take a calcium supplement from mid-pregnancy.

So why are multivitamins so popular?

Multivitamins are advertised as an essential part of the pregnancy toolkit, and maternity care providers often prescribe them.

In Australia, we found more than four in five people take multivitamins while pregnant. People see this as “insurance” to ensure they get adequate nutrition.

Our study, which uses data from a Queensland cohort of pregnant families, suggests socioeconomic factors influence the likelihood of using multivitamins in pregnancy. We found those with access to private obstetric care and health insurance, and who eat more meat (all associated with having more money) were more likely to use them.

This is not surprising given the hefty price tag. The most popular pregnancy multivitamin costs, at minimum, A$180 when taken from the month before conception and throughout pregnancy. Compare this with less than $40 for a supplement that contains only folic acid and iodine when taken for the same length of time.

Expensive brands are not better. Price is largely determined by public perception of brand quality, which is influenced by strong marketing. For most vitamins, any excess is excreted via your urine, making it, at best, expensive wee.

What happens if you have too much?

Our study found a very high dependence on supplements, particularly for folic acid, iron and iodine, to meet nutrient requirements.

If people’s diets are already providing adequate levels of those nutrients and the supplements give them extra, there’s a risk of nutrient overload.

For instance, more than one in 20 people in our study had high levels of folate intake (more than the safe “upper level of intake”). Almost half of all those in the study surpassed the upper level of intake for total iron. Virtually all of these were taking a multivitamin and had higher-than-usual blood levels of the respective nutrients.

Taking folic acid above the upper level of intake has been associated with babies being shorter at birth, lower levels of children’s cognitive development and a higher risk of childhood asthma. Folic acid supplementation, at the recommended daily dose of 400 micrograms after the first trimester, however, could be beneficial for child cognitive development although further trials would be necessary before this is routinely recommended.

High doses of iron increase the risk of high red blood cell concentration in the expectant mother. This condition increases the risk of pregnancy complications, including the baby being small for gestational age, stillbirth, gestational diabetes, pre-eclampsia and low birth weight.

When we look at iodine, about one in four expectant mums taking a multivitamin in our study had very high intakes, which has been linked to lower neurodevelopmental scores in children.

Chances are, you’re getting enough nutrients

In low- and middle-income countries, multivitamins have a place; they improve weight gain while pregnant, newborn weight and might reduce the risk of preterm birth.

In high-income countries, such as Australia, food is abundantly diverse. There are also mandatory fortification programs – folic acid and iodised salt have been used in conventional breadmaking since 2009.

In these countries, frequent multivitamin use may pose risks to both maternal and fetal health. These include developing gestational diabetes (which might be due to high iron intake) and autism spectrum disorder in children.

There are some people, however, who do not take any supplements in pregnancy. Our study, which looked at supplement intake at around 28 weeks of pregnancy, found those under 30 years old and those with a lower household income were least likely to be taking a supplement. These are the same groups that generally have a poorer diet.

What should I take?

People should look for a supplement that contains only folic acid and iodine at the recommended dose, or take these as individual supplements.

They should work closely with their maternity providers, and perhaps an accredited practising dietitian, to focus on eating enough from each of the five food groups.

Supplements should not substitute a wholefood diet. There are benefits to eating a variety of foods, which contain many complementary nutrients and other compounds we cannot obtain from supplements. Following the dietary guidelines might also save you money.

Health-care providers also need to stop routinely recommending these expensive “pink” multivitamins, and instead focus on encouraging people to eat a healthy diet. Besides folic acid and iodine, supplements should only be prescribed according to someone’s specific needs. Multivitamins don’t have a place in everyone’s pregnancy toolkit.

Shelley Wilkinson is a project officer, Department of Obstetric Medicine, Mater Mothers' Hospitals, Brisbane. She is also the director and principal dietitian of Lifestyle Maternity, a telehealth private practice for preconception, pregnancy and postnatal care.

Linda Gallo does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

The Conversation