What to Look for in a Prenatal Supplement

Prenatal supplements contain many important vitamins and minerals that support healthy fetal development. There are so many different brands to choose from, but does it really matter which one you use?

Yes! There is a huge difference in the efficacy of a prenatal vitamin when using a high quality, well research brand versus the most common ones on the market. Although the ingredients between brands can be fairly similar, the form and dose of each ingredient matters immensely. Even the most common prenatal supplements recommended by most doctors are low quality and contain inactive, poorly absorbed forms of each vitamin. This results in expensive urine as the nutrients are excreted when they are not absorbed. Additionally, these poorly absorbed nutrients often contribute to side effects such as nausea and constipation. To ensure you are getting the most out of your prenatal supplement, these are the things to look out for: 

What ingredients should I look for in a prenatal supplement?

Folic Acid

The most important component of a prenatal vitamin is the folic acid, otherwise known as vitamin B9. Folic acid is important for neural tube development, which gives rise to the brain and spinal cord in the early stages of pregnancy. With insufficient folic acid, neural tube development is disturbed and there is an increased risk for miscarriage. 

Folate vs Folic Acid

Folate (vitamin B9) is found in food such as eggs, leafy green vegetables and legumes. Folic acid is the synthetic form. To activate, folic acid must convert to folate through an enzyme known as methylenetetrahydrofolate reductase (MTHFR). Up to 40% of the population have some degree of MTHFR gene mutation, and therefore have a reduced ability to convert folic acid to the active form of folate known as L-methylfolate. If this conversion is slow, it can lead to a build-up of folic acid which can be toxic to the body. Supplementing with folate rather than folic acid can prevent this.

On a supplement bottle, look for l-methylfolate or methyltetrahydrofolate. The recommended dosage is 1mg per day to prevent neural tube defects. However, there are multiple conditions that require higher daily doses of folate. Talk to your doctor if you have diabetes, IBD, celiac disease, are on medications, have a history of neural tube defects in the family, are overweight, have liver disease or a history of long-term dieting. 


Most prenatal supplements contain B-vitamins. These are essential for energy production, brain and neurological development. However, it is important to ensure your prenatal supplement contains the most absorbable forms of each b-vitamins to optimize the effects.

Methylcobalamin is the best form of vitamin B12. It supports energy production and reduces the risk of preterm birth1. Pyridoxal 5-phosphate is the active form of vitamin B6. It is important for brain development and can help reduce symptoms of nausea and vomiting in pregnancy2. Additionally, vitamins B12 and B6 are beneficial for reducing homocysteine levels. This is an amino acid that increases miscarriage risk by causing issues with the developing placenta. Therefore, proper supplementation with B6 and B12 can help to reduce this risk.

A common side effect of taking b-vitamins is bright, highlighter yellow coloured urine. This is due to the pigment in vitamin B2 and because b-vitamins are water soluble. This is not harmful and is a completely normal process. Keep in mind that the daily requirements for b-vitamins vary from day to day, so some days the urine may be brighter than others. Additionally, days with increased water intake may yield a more diluted urine, which may appear less bright than other days.


Iron requirements increase in pregnancy and are important to prevent iron deficiency anemia. The number of red blood cells increases in the second and third trimester because the fetus and placenta require more iron and oxygen3. Supplementation is recommended because iron deficiency is associated with thyroid dysfunction, preterm birth and low birth weight4, 5.

Most prenatal supplements contain iron. However, the most commonly used form is ferrous fumarate. This form is poorly absorbed and can cause constipation. More easily absorbed forms include ferrous glycinate, ferrous succinate and ferrous gluconate. The daily recommended dose is around 20-30mg/day, however it is best to have ferritin levels checked to determine the appropriate dosage for you. It is important to take iron containing supplements away from calcium rich foods or supplements, as calcium interferes with the absorption of iron. On the other hand, vitamin C enhances iron absorption so food such as citrus fruit and dark leafy green vegetables may be beneficial. 


There is an increased demand for iodine in pregnancy due to an increase in thyroid hormone production, iodine transfer to the fetus and increased excretion of iodine through the urine. Iodine is important for the synthesis of maternal thyroid hormone, which increases by around 50% in early pregnancy6. A deficiency of iodine may contribute to congenital hypothyroidism and can impair fetal neurological development. The recommended dose is around 150mcg per day, but this may change depending on thyroid function. 


Zinc is required for protein metabolism and DNA synthesis. Therefore, it is important for growth and development. Deficiency is associated with low birth weight and congenital malformations. The recommended dose is 10-25mg/day, but in many cases doses on the higher end can cause nausea. Taking a prenatal supplement with food, breaking the tablets or spreading the dose throughout the day can help to minimize this side effect.


This nutrient is important for neurological health and fetal development. Like folate, choline is also important in preventing neural tube defects7. Most common brands of prenatal vitamins do not contain choline. Therefore, it is important to check the label. Foods high in choline include eggs, fish, chicken and turkey. The recommended dose in pregnancy is 450mg/day. 


Calcium is an important mineral for fetal skeletal development, so the demand increases during pregnancy. When deficient, calcium it is taken from the mother’s bones to support fetal growth. This can lead to brittle bones so it is important to replenish these levels through diet and supplementation. Foods high in calcium include dark leafy green vegetables, sesame seeds, dairy, almonds and legumes.

Additionally, calcium deficiency can contribute to high blood pressure in pregnancy, known as pre-eclampsia. Supplementation can help reduce this risk8. Calcium citrate is preferred, as it is absorbed better than calcium carbonate. The recommended dosage is 1000mg/day. However, the dose of calcium in a prenatal supplement is often less than this because it interferes with the absorption of iron. Therefore, additional calcium supplementation may be required.


Magnesium builds and repairs body tissues. Like many other nutrients the demand increases in pregnancy. There are many different forms of magnesium, and the form matters for the desired outcome. Magnesium glycinate or magnesium citrate are the most recommended options in pregnancy, as they are easily absorbed. Magnesium oxide has almost no bioavailability. It is used in cases of constipation due to decreased absorption and quick excretion from the body. Magnesium sulphate has been studied to reduce the risk of pregnancy induced high blood pressure, known as pre-eclampsia, but this form is not common in prenatal supplements. Additionally, magnesium can also help reduce the occurrence of leg cramps, which are a common symptom in the second and third trimester9. The recommended dose of magnesium bisglycinate and citrate is around 350mg/day. 

Vitamin D

Vitamin D is important in many processes such as modulating the immune system, regulating calcium balance and supporting thyroid function. Sufficiency of vitamin D reduces the risk of miscarriage, preterm labour and pre-eclampsia10. Most Canadians are deficient in this vitamin, so it is best to test through blood work and dose accordingly. The minimum dosage is 1000IU/day, but this is often not sufficient to reach optimal levels in our population. 

Final Thoughts on Prenatal Supplements

Taking a prenatal supplement during pregnancy is crucial to ensure all of the required nutrients are available for healthy fetal development and to prevent maternal deficiencies. High quality prenatal supplements are recommended over common brands as they contain forms of each nutrient that are more easily absorbed and utilized by the body. However, it is still important to consume a healthy, balanced diet. A supplement is not sufficient to replace the nutrients and antioxidants that are obtained from whole foods. 

It is best to start taking a prenatal vitamin several months prior to conception. If breastfeeding, you can continue your prenatal until around 4-6 weeks after stopping breastfeeding. This is recommended to ensure vital nutrients are passed to the baby via breast milk and to replenish any nutrients, such as iron that may be diminished after delivery. If you are trying to conceive or are currently pregnant or breastfeeding, I would love to help you in choosing the appropriate prenatal support for your needs. 

With love and in health,


  1. Rogne, T., Tielemans, M. J., Chong, M. F., Yajnik, C. S., Krishnaveni, G. V., Poston, L., . . . Risnes, K. R. (2017). Associations of Maternal Vitamin B12 Concentration in Pregnancy With the Risks of Preterm Birth and Low Birth Weight: A Systematic Review and Meta-Analysis of Individual Participant Data. American Journal of Epidemiology.
  2. Sharifzadeh, F., Kashanian, M., Koohpayehzadeh, J., Rezaian, F., Sheikhansari, N., & Eshraghi, N. (2017). A comparison between the effects of ginger, pyridoxine (vitamin B6) and placebo for the treatment of the first trimester nausea and vomiting of pregnancy (NVP). The Journal of Maternal-Fetal & Neonatal Medicine, 31(19), 2509-2514
  3. Bothwell, T. H. (2000). Iron requirements in pregnancy and strategies to meet them. The American Journal of Clinical Nutrition, 72(1)
  4. He, L., Shen, C., Zhang, Y., Chen, Z., Ding, H., Liu, J., & Zha, B. (2017). Evaluation of serum ferritin and thyroid function in the second trimester of pregnancy. Endocrine Journal, 65(1), 75-82. 
  5. Allen, L. H. (2000). Anemia and iron deficiency: Effects on pregnancy outcome. The American Journal of Clinical Nutrition, 71(5).
  6. Yarrington, C. D., & Pearce, E. N. (2011). Dietary Iodine in Pregnancy and Postpartum. Clinical Obstetrics and Gynecology, 54(3), 459-470
  7. Radziejewska, A., & Chmurzynska, A. (2019). Folate and choline absorption and uptake: Their role in fetal development. Biochimie, 158, 10-19.
  8. Khaing, W., Vallibhakara, S. A., Tantrakul, V., Vallibhakara, O., Rattanasiri, S., Mcevoy, M., . . . Thakkinstian, A. (2017). Calcium and Vitamin D Supplementation for Prevention of Preeclampsia: A Systematic Review and Network Meta-Analysis. Nutrients, 9(10), 1141
  9. Supakatisant, C., & Phupong, V. (2012). Oral magnesium for relief in pregnancy-induced leg cramps: A randomised controlled trial. Maternal & Child Nutrition, 11(2), 139-145
  10. De-Regil, L. M., Palacios, C., Lombardo, L. K., & Peña-Rosas, J. P. (2016). Vitamin D supplementation for women during pregnancy. Cochrane Database of Systematic Reviews

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