Prenatal vitamins are often the first thing that I recommend to individuals who are trying to conceive. A high quality prenatal can help improve implantation, prevent miscarriage and support healthy fetal development. However, most people are taking poor quality supplements that don’t provide as many benefits as the well researched professional brands. When it comes to optimizing fertility, something as simple as a proper prenatal vitamin can have a huge impact on the success of a cycle.
So what’s the difference between the common prenatal you can buy at your drug store versus a professional brand? Well, although the ingredients may look very similar, the drug store brands often contain inactive forms of each vitamin that are poorly absorbed. Without optimal absorption, the expected therapeutic effect of each vitamin is limited and side effects such as nausea and constipation may result. Here are the things to look for when you’re purchasing a prenatal supplement:
Ingredients to look for in a prenatal vitamin
This is the most important ingredient in a prenatal vitamin, and is often what sets it apart from a regular multivitamin. Folate, otherwise known as vitamin B9 is very important for fetal neural tube development in the early stages of pregnancy. The neural tube gives rise to the brain and spinal cord and without adequate development the pregnancy is often not viable and there is an increased risk for miscarriage. Folate is also important for egg quality, maturation and embryo implantation.
What is the difference between folate and folic acid?
Many common brands of prenatal vitamins use folic acid, which is the synthetic form of folate. Folic acid needs to be converted in the body to folate by an enzyme called methylenetetrahydrofolate reductase (MTHFR). However, up to 40% of the population has some degree of MTHFR gene mutation that limits their ability to convert folic acid into the active form of folate (L-methylfolate). Therefore, it is best to just supplement with active folate to ensure you are obtaining the benefits. On the label, look for l-methylfolate or 5-methyltetrahydrofolate (5MTHF). This should be the first thing you look for. If the form is folic acid, move on to the next!
Recommended dosage: 1mg per day. 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 as these factors can change the required dose.
All prenatal supplements contain a variety of b-vitamins which are essential for energy production and neurological development. Like folate, you want to make sure you are buying a supplement that has activated forms of each b-vitamin. The first one to look for is vitamin B12. You want methylcobalamin rather than cyanocobalamin or hydroxycobalamin because it is better absorbed. Vitamin B12 is important because a deficiency can lead to an increased risk of preterm birth1.
Additionally, vitamins B12, B6 and folate reduce levels of an amino acid called homocysteine. Elevated homocysteine has been associated with an increased risk of miscarriage and therefore it’s important to have adequate levels of these vitamins to improve the chances of a successful pregnancy2. Vitamin B6 is also often recommended to reduce symptoms such as nausea and vomiting in pregnancy. The active form of vitamin B6 is 5-pyridoxal-phosphate.
In pregnancy, the requirements for iron increase. Most prenatal supplements contain iron to reduce the risk of iron deficiency anemia and support the growing baby. Iron deficiency has been associated with an increased risk of preterm birth and low birth weight3. It can also affect thyroid function which is crucial to pregnancy maintenance4. Common brands of prenatal vitamins contain iron in the form of ferrous fumarate. This form is not easily absorbed and often contributes to constipation. When reading the ingredients, look for more bioavailable forms such as ferrous (iron) glycinate, ferrous succinate or ferrous gluconate. The recommended dose is 20-30mg/day but it is important to test your ferritin levels to ensure you are receiving the dose that is most appropriate for you as an individual.
Like iron, the demand for calcium increases in pregnancy to support skeletal development. If levels are low, there is an increased risk for pre-eclampsia (high gestational blood pressure)5. Calcium can be obtained through foods such as leafy greens, sesame seeds, almonds, legumes and dairy. In supplement form, calcium citrate is preferred over calcium carbonate because it is better absorbed. The recommended dosage is around 1000mg/day, however this is often not present in a prenatal because calcium interferes with iron absorption. Therefore, additional supplementation away from prenatal intake may be required throughout pregnancy.
Magnesium is required to build and repair tissues, and therefore the demand increases in pregnancy. Many women are deficient in magnesium, so additional supplementation may be required. Magnesium bisglycinate or magnesium citrate are often the recommended forms for pregnancy as they are better absorbed. Magnesium oxide is quickly excreted from the body and is often used to move the bowels in cases of constipation, and therefore has very limited absorption. In the second and third trimesters, magnesium can also be recommended to reduce the occurrence of leg cramps, which is a common symptom of pregnancy6. The recommended dosage is 350-500mg/day, depending on the individual and the trimester.
Thyroid hormone production increases by around 50% in pregnancy. Iodine is important for the synthesis of maternal thyroid hormone which is required for pregnancy maintenance. A deficiency of iodine can lead to congenital hypothyroidism or impaired fetal neurological development. The recommended dose is around 150mcg per day, but this may change based on each individuals thyroid function in blood work.
Zinc is important for fetal growth and development because it is required for DNA synthesis and protein metabolism. A deficiency can lead to congenital malformations or low birth weight. The recommended dose is around 10-25mg/day, but higher doses of zinc can contribute to nausea. If your prenatal supplement is causing nausea, consider taking it with food, breaking the tablet in half or spreading your dosages throughout the day. Many high quality prenatal vitamins require 3 capsules or tablets per day so it is often recommended to take them with each meal.
Choline is often not found in common brands of prenatal supplements. However, it is almost as important as folate. Choline supports neurological development and prevents neural tube defects7. Foods high in choline include eggs, beef, fish, chicken, soybeans and turkey. If you consume a plant-based diet you’ll want to ensure that your prenatal contains adequate amounts of choline, B12, iron and folate. The recommended dosage is 450mg/day, so it is recommended to eat choline rich foods on top of the dose in your prenatal.
Vitamin D is important for every individual, pregnant or not. It is required in every cell of the body and is important for immune system regulation, supporting thyroid function, regulating calcium balance and supporting implantation. Adequate levels of vitamin D reduce the risk of miscarriage, preterm labour and pre-eclampsia8.
It is important to get blood levels of vitamin D tested to determine the appropriate dose for you. Optimal levels on bloodwork are at least 100nmol/L. The minimum dosage is 1000IU/day, but this is often not sufficient to reach optimal levels since most Canadians are very deficient. A dosage of above 1000IU/day requires a prescription so many prenatal vitamins only contain a very small amount of Vitamin D, and therefore additional supplementation is often required. Talk to your MD or ND about testing so you can receive an appropriate dose on top of your prenatal.
It’s clear that prenatal supplements are crucial for healthy fetal development and to prevent maternal nutrient deficiencies during pregnancy. If possible, choose a high quality prenatal vitamin that contains the active form of each nutrient to optimize absorption and reduce the risk of complications such as miscarriage, premature birth and pre-eclampsia. It is best to start prenatal supplementation 3-6 months before conception but if this is not possible, start as soon as you can. I often recommend to continue a prenatal during breastfeeding to ensure adequate nutrients are passed via breast milk and to replenish any deficiencies in the mother after birth.
Talk to your doctor before changing any part of your supplement routine, and to determine what may be the best options for you as an individual.
Dr. Gina Neonakis, ND
- 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.
- Serapinas, D., Boreikaite, E., Bartkeviciute, A., Bandzeviciene, R., Silkunas, M., & Bartkeviciene, D. (2017). The importance of folate, vitamins B6 and B12 for the lowering of homocysteine concentrations for patients with recurrent pregnancy loss and MTHFR mutations. Reproductive Toxicology, 72, 159–163
- Allen, L. H. (2000). Anemia and iron deficiency: Effects on pregnancy outcome. The American Journal of Clinical Nutrition, 71(5).
- 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.
- 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
- 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
- Radziejewska, A., & Chmurzynska, A. (2019). Folate and choline absorption and uptake: Their role in fetal development. Biochimie, 158, 10-19
- 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