The Critical Role of Prenatal Vitamins

The Critical Role of Prenatal Vitamins

Written by: Marci Clow, MS, RDN

Nutritious foods should always be the primary source of prenatal nutrition. Yet, the nutrient demands of pregnancy, compounded by factors such as nausea from the surge of pregnancy hormones, can make it difficult to get adequate nourishment through diet alone. This is where prenatal vitamins come into play. This article explores supplemental nutrients to consider for assurance you are doing everything in your power to fuel a healthy pregnancy and support the miraculous development of a new life. 

What are the Benefits of Prenatal Vitamins?

While numerous factors come into play, good nutrition is an unequivocal determinant of a healthy pregnancy and baby. Prenatal vitamins deliver supplemental nutrients to complement a healthy diet; they provide a balanced combination of nutrients, including those needed in higher amounts during preconception, while pregnant, and when breastfeeding. The Dietary Guidelines for Americans 2020-2025 emphasize that nutritional needs should be met primarily through the consumption of nutrient-dense foods. However, typical American diets tend to fall short in several nutrients that can impact a healthy pregnancy. Taking a prenatal vitamin can:

● Help fill in nutrient shortfalls in the diet.
● Provide nutrients for baby’s growth and development.
● Provide nutrients that are depleted during pregnancy.
● Decrease mom’s nausea, heartburn, and fatigue.
● Support a healthy delivery and recovery.

The bottom line is that while nourishing the body before and throughout pregnancy with a nutrient-rich diet should be the first and foremost way to achieve adequate nutrient levels during gestation, a smart supplementation program can fill in dietary nutrient gaps, play a critical role in pregnancy outcome, and is a relatively low-cost component that can improve the chances of having a healthy baby.

What Nutrients Are of Key Importance to Mom & Baby?

While the nutritional status of a mom-to-be has a huge impact on fetal growth and development, the female body is resilient. It can dictate the need for some nutrients by making them more bioavailable during these periods. On the other hand, the fetus acts as a nutrient parasite, placing the mother at risk for deficiencies as the fetus gets preferential treatment. Although all nutrients have a part in supporting a healthy pregnancy, the following are of particular importance for supplementation:

● Folic acid: Folic acid is the synthetic form of folate used in supplements and fortified foods. It is essential for its function in preventing birth defects of the brain and spinal cord called neural tube defects (NTDs). The neural tube starts out as a tiny ribbon of embryonic tissue, and by the 28th day, a spinal cord is beginning to form. When this process goes awry, and the neural tube does not close completely, defects can result. According to the March of Dimes, 70% of NTDs could be prevented with folic acid supplementation. It has been estimated that 40% of women may have a genetic mutation, known as MTHFR, that prevents the conversion of folic acid into methylfolate (the active form the body needs). For that reason, some healthcare practitioners recommend that prenatal vitamins contain the methylfolate form of folic acid. Good dietary sources of naturally occurring folate include dark green leafy vegetables, asparagus, citrus fruits, legumes, and beans. Foods fortified with synthetic folic acid include cereals and grain products. The recommended dietary allowance (RDA) for folate during pregnancy is 600 mcg/d.

FUN FACT: Current legislation in California (amended 5/8/2024) would require corn masa flour, which is used to make tortillas, to be fortified with folic acid as a measure to prevent NTDs in the Latina population.

● Iron: The blood volume of the pregnant woman increases significantly during pregnancy. Iron is required to synthesize hemoglobin (the oxygen transport protein in the blood) in both maternal and fetal red blood cells. The fetus acts as a parasite, assuring its own production of hemoglobin by drawing upon iron stores from the mother, placing the mother at risk for iron-deficiency anemia and increasing her chance of developing toxemia, labor, and delivery complications, and delivering a preterm or low-birth-weight infant. Good dietary iron sources include lean red meat, poultry, beans, spinach, and fortified breakfast cereals. The RDA for iron during pregnancy is 27 mg/d.

● Calcium and Vitamin D: Calcium is a critical mineral for both maternal health and fetal development. Hormonal changes in the mom-to-be can affect calcium metabolism, leading to disruptions in healthy blood pressure, increased risk for preterm delivery, and leg cramps. Calcium is crucial for fetal bone development throughout gestation; if calcium intake is chronically low, calcium is leached from the mother’s bones for the fetus. During the third trimester, when skeletal growth is rapid, the fetus can acquire as much as 250-300 mg of calcium from the mother daily, which is equivalent to the amount found in a cup of milk. Good dietary sources of calcium include dairy products, broccoli, kale, sardines with bones, and fortified products, such as juice, plant-based milk, and breakfast cereal. The RDA for calcium during pregnancy is 1,000 mg/d.
o Vitamin D works with calcium to help build bones and teeth. A deficiency in this essential vitamin has been associated with serious pregnancy complications, including pre-eclampsia, low birthweight, and preterm birth. Vitamin D is produced by the body when exposed to sunlight, but it is limited in the food supply to oily fish, eggs, and fortified products. The RDA for vitamin D during pregnancy is 600 IU/d.

● Docosahexaenoic acid (DHA): DHA is an omega-3 fatty acid important for developing the fetal eye, brain, and central nervous system. It is the most abundant structural fatty acid in these tissues. Throughout the third trimester of pregnancy, DHA is passed to the fetus through the placenta, an action that has been linked to the development of an infant’s brain and eventual ability to learn, judge, and concentrate. DHA is also vital for healthy maternal brain function, with several studies suggesting a role in reducing the risk of postpartum depression and lowering the risk of preterm birth. Dietary DHA is most abundant in fish and seafood, although a small amount of alpha-linolenic acid from plant oils is converted to DHA. Certain brands of eggs and milk are also fortified with DHA. During pregnancy, inadequate intake is a concern because some women may choose to limit fish intake due to fear of exposing the fetus to mercury, an aversion to the smell of fish or burp-back from fish oil supplements, or because they adhere to a plant-based diet. Although there is no RDA for DHA, several expert panels in the US recommend at least 200 mg/d. NOTE: Many prenatal vitamins do not contain DHA, so a separate supplement is needed to get the recommended daily dose.

FUN FACT: Taking a polar lipid form of supplemental algal DHA, such as Orlo’s Active Prenatal DHA, provides a mercury-free, highly bioavailable, vegan source of easily absorbed DHA with no burp-back or aftertaste.

● Other nutrients and role in prenatal care:
o Choline is needed for healthy fetal brain and tissue development.
o Magnesium is involved with hundreds of biochemical reactions in the body and is needed in higher amounts during pregnancy.
o Vitamin K works alongside calcium and vitamin D to support bones and also plays a role in blood clotting.
o Iodine requirements increase during pregnancy to support thyroid function and brain/nervous system development.
o Selenium is also required to activate thyroid hormones.
o Zinc is needed to support rapid cell growth.
o Vitamin B6 supports cell growth and can help with nausea.
o Vitamin C helps increase iron absorption.
o B12 is needed to make red blood cells and for the growth of the nervous system.

How Do I Choose the Right Prenatal Vitamin?

When it comes to choosing the right prenatal vitamin, the wide array of options can be quite overwhelming. One of the top reasons cited for noncompliance with prenatal vitamins is nausea and digestive upset, which can already be an issue for moms-to-be who are suffering from morning sickness. Other aversions include burp-back, constipation, needing to take more than once daily, and difficulty swallowing.

When selecting a prenatal, common questions include: Do I select a tablet, a capsule, or a soft gel, and how am I meant to swallow these giant horse pills? Or should I take a chewable, a powder, a liquid, or a gummy? Is a 3- or 6-per-day dose better than a 1-per-day? The honest answer is that it really depends on your personal preference, as long as the formulation contains the key critical nutrients needed to support a healthy pregnancy. Divided doses may be gentler on the stomach, as will taking the vitamins with meals. Asking your doctor, midwife, or pharmacist for their recommendation is always a good idea so they can assure you the formulation is adequate and will not interact with any medications you may be taking.

Unfortunately, there is no standard for prenatal supplements, so they can vary widely in their content, quality, and dosage. For those needing additional assistance in selecting the best prenatal for their specific needs, the Neurological Health Foundation has developed an evidence-based free app called Prenatal Rater that is worth checking out.

● Supplemental iron is known to cause constipation, yikes! Look for non-constipating forms of iron, such as ferrous bisglycinate (an iron amino acid chelates), or select a slow-release iron.
● If you have been diagnosed with an MTHFR mutation, select a prenatal with the methyl folate form of folic acid.
● Look for prenatal supplements that have been third-party tested to ensure they contain what is indicated on the label and to ensure the purity of the product., NSF International, UL, and USP are some well-known options for third-party testing.
● More expensive doesn’t necessarily mean better. There are many options at various price points; some may have a higher retail price but provide more than a 1-month supply, and others that seem more expensive may already include DHA and, therefore, not require a separate supplement purchase.

How to Be Sure You Are Taking Prenatal Vitamins Effectively

The question of when to start taking prenatal vitamins is a common one, and the answer is fairly simple: ideally before conception. This recommendation is related to the need for folic acid in the development of the brain and spinal cord, which begins to form in the first few weeks of pregnancy before many women even know they are pregnant. Many healthcare practitioners recommend that all women of reproductive age take a multivitamin that contains 400 mcg of folic acid and then switch to a prenatal that contains 600 mcg if they become pregnant.

Once you select and begin taking a prenatal vitamin, make sure you are following the recommended daily dosage. As discussed above, prenatal vitamins can range in serving size, so you should not take more than the recommended amount of your prenatal vitamin per day, as some ingredients, such as vitamin A, can potentially cause birth defects at higher doses than the RDA. To spell it out: If the serving size is 1 per day, don’t take 2. If the serving size is 6 per day, don’t take 3. If you think you need an additional amount of a certain nutrient based on your diet or lifestyle or if you have a history of a child born with an NTD check with your healthcare practitioner to adjust dosages or adding a separate supplement.
In addition to the question of when to start taking a prenatal vitamin, some might wonder when you should stop. The general recommendation is to continue taking prenatal multivitamins and DHA supplements as directed the entire time your child is breastfed.

TIPS for Overcoming Common Pregnancy Discomforts

● Constipation: Hormonal fluctuations during pregnancy in addition to iron supplements may cause constipation. To help ward off constipation drink plenty of fluids, include more fiber (fruits, veggies, grains, beans) in your diet, engage in physical activity regularly, and make sure your prenatal vitamin has non constipating iron.

● Nausea: Pregnancy hormones can also cause nausea, which is known as morning sickness, but it can really occur at any time during the day. Some tips to manage nausea include eating small frequent meals and snacks, staying hydrated between meals, limiting spicy and fatty foods, avoiding lying down right after eating, taking a walk following meals, and trying ginger and vitamin B6 to ease nausea.

Key Takeaways

The optimal way to achieve a solid nutritional foundation during pregnancy is through a wide variety of nutritious whole foods. However, certain nutrients might be lacking in the typical American diet or are needed in higher amounts during pregnancy to optimally support maternal health, fetal development, and the best pregnancy outcome. Vitamins, minerals, and DHA supplements specifically formulated to meet the needs of pregnant women are necessary components that all women who are pregnant or considering becoming pregnant should discuss with their healthcare team. Supplements should always be used as their name implies, which is to supplement nutrients that might be missing from the diet or to meet the recommended nutritional needs of a specific life stage.

Adams JB, Kirby JK, Sorensen JC, et al. Evidence based recommendations for an optimal prenatal supplement for women in the US: vitamins and related nutrients. Matern Health Neonatol Perinatol. 2022;8(1):4.

Brown B, Wright C. Safety and efficacy of supplements in pregnancy [published correction appears in Nutr Rev. 2020;78(9):782]. Nutr Rev. 2020;78(10):813-826. doi:10.1093/nutrit/nuz101

Destaillats F, Oliveira M, Bastic Schmid V, et al. Comparison of the incorporation of DHA in circulatory and neural tissue when provided as triacylglycerol (TAG), monoacylglycerol (MAG) or phospholipids (PL) provides new insight into fatty acid bioavailability. Nutrients. 2018;10(5):620. doi:10.3390/nu10050620

DiNicolantonio JJ, O’Keefe JH. the importance of marine omega-3s for brain development and the prevention and treatment of behavior, mood, and other brain disorders. Nutrients. 2020;12(8):2333.

Guesnet P, Alessandri JM. Docosahexaenoic acid (DHA) and the developing central nervous system (CNS) - Implications for dietary recommendations. Biochimie. 2011;93(1):7-12. doi:10.1016/j.biochi.2010.05.005

Koletzko B, Lien E, Agostoni C, et al. The roles of long-chain polyunsaturated fatty acids in pregnancy, lactation and infancy: review of current knowledge and consensus recommendations. J Perinat Med. 2008;36(1):5-14. doi:10.1515/JPM.2008.001

Pregnancy and lactation. Linus Pauling Institute, Micronutrient Information Center. Updated, March 2016. Accessed May 10, 2024.

Dietary Guidelines for Americans, 2020-2025. 9th ed. U.S. Department of Agriculture and U.S. Department of Health and Human Services. December 2020. Accessed May 15, 2024.

Vitamins and other nutrients during pregnancy. March of Dimes. Updated September 2020. Accessed May 8, 2024.


Marci Clow is a registered dietitian nutritionist and the founder of Clowt Content, an organization which provides evidence-based content on a wide range of food and nutrition topics. The information presented here is intended only to be educational and provide readers with information; it is not an endorsement of the writer for any particular product. These statements have not been evaluated by the Food and Drug Administration. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease.



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