Supplements During Pregnancy: Folic Acid, Iodine and Vitamin B12

Doctors often recommend that women who are pregnant or wanting to become pregnant should take supplements containing folic acid, vitamin B12, and iodine. This kind of supplement is recommended during pregnancy and a month before conception. Let's take a look at the benefits of taking them.

Reviewed and approved by the doctor María Belén Del Río.

Written by Sara Viruega Encinas

Last update: 27 December, 2022

In pregnancy your needs for energy, proteins, vitamins, and minerals all increase. In principle, your diet should be your main source of the necessary nutrients during pregnancy. Nonetheless, sometimes it’s recommended to take supplements during pregnancy to assure you’re getting sufficient dosages of some essential vitamins or minerals.

Early pregnancy is a critical stage of fetal development. An excess or a lack of certain nutrients during this stage can increase the risk of having certain diseases in adult life.

Some micronutrients like folic acid, vitamin B12, and iodine are of special importance. These are the vitamins often contained in the commercial supplements available for pregnant women. Let’s look more closely at what each of these nutrients do and why doctors recommend them.

What is a supplement?

While the exact formulations of each commercial brand vary, most supplements targeted for pregnant women contain folic acid, vitamin B12, and iodine, which doctors recommend widely during pregnancy. There is a heightened need for these nutrients during pregnancy and our diets often don’t cover the need.

Tablets of these supplements may contain dosages like the following:

• Folic Acid: 400 mg
• Vitamin B12 2 mg
• Potassium Iodine 262 mg (the equivalent of 200 mg of iodine)

These supplements are indicated for the prevention of the disorders that result because of a lack of iodine, folic acid, or vitamin B12 in pregnant women. Doctors also recommend taking them for at least a month before conception to prevent defects in the neural tube and other neural disorders in the fetus.

You should check the information contained on the pharmaceutical drug Data Sheet or Consumer Medicine Information (CMI) of the particular supplement you’re taking to know the correct dosage.

Your recommended dosage will likely be one tablet a day beginning one month before conception until the end of the first trimester of pregnancy. Nonetheless, sometimes it’s recommended to continue taking the supplements until the baby is born and even during lactation.

Let’s look more closely at the composition of these supplements to understand the importance they have.

Supplements during pregnancy: Folic acid

Folic acid is a group B vitamin; specifically, it’s vitamin B9. It’s a key part of the synthesis, repair, and functioning of DNA and RNA.

A deficiency in folic acid will result in the defective synthesis of DNA in any cell that tries to replicate itself. For this reason, the consequences of a deficiency in folic acid are more serious in the tissues with the greatest rate of growth and cellular division.

Folic acid has crucial importance in the formation of the central nervous system. This is because it plays a role in the biosynthesis of amino acids and nucleic acids. In pregnancy, this process takes place between 15–28 days after conception.

The folic acid taken as a supplement is absorbed better than the folic acid you get more regularly from your diet. For this reason, it’s vitally important to take a supplement to cut the risk of developing neural tube defects in the fetus, like spina bifida.

Supplements during pregnancy: Vitamin B12

Another name for vitamin B12 is cyanocobalamin. It’s necessary for DNA synthesis and it’s important to the process of cellular division. Vitamin B12 is needed for the metabolism of lipids, proteins, and carbohydrates and it’s necessary for the synthesis of myelin and hematopoiesis.

Related to folic acid, vitamin B12 interacts with it in a very complex way. Vitamin B12 is one of the necessary cofactors in the metabolic process involving the methionine synthase enzyme. Therefore, the absence of this vitamin is also a limit on the capacity for the body to adequately activate folic acid. 

In addition, vitamin B12 is also involved in the capacity for the cells to capture folic acid. It’s clear that a cell that is deficient in B12 will also be deficient in folic acid.

Potassium iodine

Iodine is an essential element for the synthesis of hormones produced by the thyroid. These hormones are necessary throughout all life stages for the correct functioning of the central nervous system:

• Thyroxine
• Triiodothyronine

These hormones are especially important to the fetus in the development phase. An insufficiency in these hormones is accompanied with anatomic and functional alterations in the brain that are irreversible and permanent.

In addition to synthesizing the thyroid hormones, iodine also influences the functions of the thyroid in a direct way. Moreover, it also has a great influence on cellular proliferation.

Insufficient iodine is the principal preventable cause in the world of brain lesions in fetuses and nursing babies. It’s also responsible for a delay in psychomotor development in many young children. A lack of iodine can cause hypothyroidism and brain damage.  

Secondary effects of supplements

Any adverse reactions that can result from taking folic acid and vitamin B12 supplements are very infrequent. It’s considered a very safe supplement, especially in pregnancy.

In the case of an overdose, the most problematic substance is iodine. This is because it crosses the placenta, and the fetus is sensitive to it. You should be careful not to take too much iodine.

If you take large amounts of iodine for long periods of time, you can manifest what doctors call iodism or iodine poisoning. Some of these symptoms are:

• Metallic taste in the mouth
• Burning sensation in mouth and throat
• Painful sensitivity in the teeth and gums

• Increase in salivation
• Sneezing
• Acute runny or stuff nose
• Irritated eyes and swollen eyelids
• Strong headaches
• Productive cough
• Skin rash
• Gastrointestinal discomforts
• Diarrhea

You can also experience hyperplasia in the thyroid gland, adenoma in the thyroid, goiter, or serious hyperthyroidism. Nonetheless, the signs and symptoms of iodine poisoning tend to resolve quickly when the patient suspends treatment.

The indiscriminate use of supplements during pregnancy can have undesirable secondary effects if the expectant mother takes an excessive dosage of vitamins and minerals. Thus, it’s important to always follow the advice of your specialist.