Preconception and Pregnancy: A Nutritional Guide for Clinicians 

 In Endocrinology


While it is generally understood that maternal preconception health and nutrition is important, the opportunity to use the perinatal period for programming a child’s future health and disease risk is becoming increasingly evident. While future parents may start to think about behavioral change when they are trying to conceive, cohort studies suggest that the impact of dietary patterns up to 3 years prior to conception may influence pregnancy and fetal outcomes.1  

In pregnancy, physiologic adaptations begin immediately after conception, which change the mother’s nutritional needs. During the first 2-8 weeks of pregnancy, organogenesis occurs and neural development begins at a rapid rate. In the 2nd and 3rd trimesters, the fetus accumulates nutrients to be used after birth, highlighting the essential need for adequate maternal stores.2 

What We Can Offer 

As primary healthcare providers trained in clinical nutrition, naturopathic doctors are in a prime position to educate our patients on the impacts of lifestyle choices on the health of the next generation. This review will summarize several key nutrients crucial to early childhood development and provide concise guidelines for clinicians working with expectant mothers. I will also focus on the indications, dosages, and safety of nutritional supplementation during pregnancy, along with special considerations for specific populations. 


Folate, or vitamin B9, is essential for DNA synthesis, amino acid metabolism, and erythropoiesis.2 In pregnancy, folate is required for normal development of the neural tube in the fetus within 28 days of conception; supplementation within this critical period can reduce the risk of neural tube defects by 70%.1,2 The 2-3 months before and after conception is also considered a critical period in fetal and placental development, during which some changes are irreversible.1 In addition, adequate folate supplementation is thought to decrease the risk of miscarriage, stillbirth, and neonatal death, as well as preeclampsia and low birth weight.1 

The naturally occurring form of this vitamin is found in legumes, leafy green vegetables, broccoli, asparagus, and avocado. Many grains and cereals are also fortified with folic acid.3 A supplemental daily dose of between 400 mcg – 1 mg should be started 3 months prior to planning a pregnancy.3 


Iron is a trace mineral required for proteins such as hemoglobin, which allows red blood cells to transport oxygen throughout the body. In pregnancy, there are high demands for iron as the blood volume expands to meet the demands of the growing fetus. In fact, the neonatal brain requires about 60% of total body energy reserves during development.2 Iron deficiency in pregnancy, and subsequently in the first 6 months of an infant’s life, can lead to irreversible and lifelong neurological effects. Additionally, iron-deficiency anemia in the mother is a risk factor for preterm labor, low birth weight, and is predictive of iron deficiency in infants after birth.3 

Identifying iron deficiency early on in pregnancy is crucial because, even if it is eventually corrected, repletion after a certain point can still fail to correct structural impairments that may have occurred in the developing fetal brain.1 A Cochrane review has shown that, while iron supplementation can resolve maternal anemia, it is less clear what the determinants are for resolving other maternal and neonatal outcomes that result from it.4 

The recommended supplemental iron intake during pregnancy is 27 mg per day, with an upper limit of 45 mg per day, unless a woman is being treated for iron deficiency anemia. Testing should be used to guide individual recommendations. Although early identification and correction is imperative, excess supplementation can be harmful. 

Meat, poultry, fish, and seafood provide heme sources of iron, which has higher bioavailability. Absorption of non-heme iron from foods such as eggs, legumes, tofu, nuts, seeds, and grains can be enhanced by combining them with foods rich in vitamin C. 


Calcium is critical for fetal bone and tooth development, maintenance of the maternal skeleton, and smooth muscle contractions. Calcium is also a critical factor in blood pressure regulation via calcium-dependent hormones and the renin-angiotensin pathway, and it is a special consideration for women at risk of preeclampsia.  Most of the transfer of calcium from the mother to the fetus occurs in the 3rd trimester. Approximately 80% of the calcium in the fetal skeleton is transferred at that time.2 

The best sources of calcium are dairy foods, including milk, yogurt, cheese, and fortified non-dairy alternatives. Additional sources include almond butter, nuts, tofu, canned fish (with bones), and dark green vegetables. The recommended calcium intake in pregnancy is 1000 mg per day.3 Calcium supplementation of 500 mg per dose (at the most) should be considered only when adequate calcium cannot be attained through food sources. An increase in cardiovascular risk with calcium supplementation may be of concern; however, it is not currently well supported by evidence.5 

Vitamin D 

Vitamin D assists in calcium regulation and supports the fetal skeleton and tooth enamel development. Newer evidence also suggests a role of vitamin D in the developing the immune system.2 Because it has been identified as promoting T-helper 2 (Th2) cell activity, the immunomodulatory role of vitamin D is emerging as a protective factor in cases of recurrent pregnancy loss.6 

Vitamin D deficiency in pregnancy is associated with a number of adverse outcomes, including gestational diabetes, preeclampsia, preterm birth, emergency C-section delivery, low birth weight, and asthma.1,3 With prevention in mind, the timing of supplementation of this nutrient may be crucial. One study suggests that the most substantial benefit of vitamin D in reducing the risk of gestational diabetes requires that supplementation begins pre-pregnancy or within the first 6 weeks of pregnancy.2 Additionally, maternal vitamin D deficiency is correlated with an increased risk of postpartum depression. When vitamin D levels are <50 nmol/L, the risk can be up to 2.67 greater.7 

Food sources of vitamin D are limited and include cow’s milk or fortified, plant-based beverages. Prenatal multivitamins commonly contain between 600 -1,000 IU of vitamin D. Ideally, any supplementation of vitamin D should be based on testing. 


Iodine is a mineral required to synthesize thyroid hormones thyroxine and triiodothyronine, which regulate metabolic processes, skeletal development, and nervous system development in the fetus.2 During pregnancy, iodine requirements increase significantly. The developing fetus relies on thyroxine produced by the mother and delivered via the placenta until approximately 17 to 19 weeks’ gestation (when the fetal thyroid gland becomes functional).2,3 

Iodine deficiency in pregnancy can lead to miscarriage, stillbirth, goiter, or impaired physical and cognitive development.3 Populations at risk for iodine deficiency include individuals with subclinical hypothyroidism and vegans.3 Excessive iodine intake can also alter thyroid function, which is particularly problematic in individuals with anti-thyroid antibodies.3  

The daily requirement for iodine in pregnancy is 220 mcg, while the upper limit for iodine intake is 1100 mcg per day.3 Examples of dietary sources of iodine include iodized salt, freshwater fish, eggs, and non-organic dairy.3 


Choline is an essential nutrient required for synthesizing phospholipids and neurotransmitters, such as acetylcholine. During pregnancy and in a child’s early years, choline intake is essential for proper cognitive development, learning, and memory. Inadequate choline intake during critical periods of fetal and infant development may result in lifelong changes in the structure and function of the brain – including the development of the hippocampus – which begins to develop during the later stages of pregnancy and continues through the first four years of life.2 

Choline is found in animal foods, such as eggs, beef, chicken, fish, and dairy, but it is also present in cruciferous vegetables, leafy greens, beans, nuts, and seeds.  Some seeds and nuts rich in choline are flax seeds, pumpkin seeds, and cashews. Despite being present in a variety of foods, women often fall short of the minimum recommended daily intake during pregnancy, and choline is not standard in all prenatal multivitamins.8 Current recommendations suggest that pregnant women should aim for 450 mg of choline per day, and 550 mg per day during lactation. Some studies suggest further benefit with a higher intake of choline during late pregnancy – upwards of 900 mg of choline per day.9, 10 


Omega-3 polyunsaturated fatty acids include alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). The physiologic benefits of omega-3 fatty acids in pregnancy are primarily attributed to EPA and DHA. DHA is actively transported across the placenta to support high fetal demands, particularly during the last trimester of pregnancy. DHA is essential for optimal fetal development as it becomes structurally incorporated into the cell membranes of the brain and retina. 

Supplementation with omega-3s in pregnancy has been shown to support healthy birth weight, reduce the risk of preterm delivery, and improve short- and long-term neurodevelopment and visual acuity.3 Further benefits include a reduced risk of eczema, allergy, and asthma.2 In addition, research suggests that DHA alters the infant epigenome during the 2nd half of pregnancy and can alter developmental programming.2  

EPA and DHA are primarily found in fish and shellfish. In pregnancy, fish sources that are low in mercury are preferable and include salmon, herring, Atlantic mackerel, sardines, and rainbow trout. Plant sources of omega-3s, such as walnuts, flaxseed, canola, and soybean oils, contain ALA, which is poorly converted to EPA and DHA in humans.  

A daily intake of a minimum of 200 mg of DHA in pregnancy is needed, although attaining 1-2 g of EPA plus DHA daily may have a favorable effect.3 No harmful effects in pregnancy have been observed with dosages up to 2.7 g/d 11.  

Key Nutrients for Pregnancy 

Nutrient Target Intake Food Sources Special Considerations Benefits 
Folate 400 mcg to 1 000 mg per day; begin 3 months prior to conception Legumes, leafy green vegetables, broccoli, asparagus, avocado; fortified in grains and cereals L-methylfolate may be preferrable over folic acid 
Prevents neural tube defects, decreases risk of miscarriage, stillbirth, neonatal death, preeclampsia and low birth weight 
Iron 27 mg/d; upper limit of 45 mg/d unless a woman is being treated for iron deficiency anemia; testing during preconception and pregnancy recommended; calcium supplements should be taken at least 2 hours apart from iron-containing supplements  Heme iron: meat (beef, pork, lamb, etc), poultry (chicken, turkey), fish and seafood; non-heme iron: eggs, legumes, tofu, nuts, seeds, and grain products;  cereals may be enriched Vegans and vegetarians; absorption of non-heme iron is improved when combined with foods rich in Vitamin C; absorption of non-heme iron from foods high in phytates (legumes, such as lentils, beans, split peas, and soybeans) is improved when soaked overnight or sprouted; tea and coffee should be separated from iron by 1 hour  Reduces risk of low birth weight, preterm birth; needed for fetal growth and brain development 
Calcium 1,000 mg/d; upper limit is 2,000 mg/d; supplementation should not exceed 500 mg in a single dose Dairy and fortified non-dairy alternatives Vegans; lactose intolerance; individuals at risk for preeclampsia  Critical for fetal bone and tooth development, smooth muscle contraction, and blood pressure 
Vitamin D Recommendations range from 600-4,000 IU/day; testing during preconception and pregnancy is recommended to determine individualized regimen  Dairy products and fish, including salmon, herring and rainbow trout  Populations with limited sun exposure Supports development of tooth enamel, the skeletal system, and the immune system; may reduce the risk of recurrent pregnancy loss, gestational diabetes, preeclampsia, preterm birth, emergency C-section delivery, low birth weight, and asthma 
Iodine 220 mcg/d; upper limit is 1,100 mcg/d Iodized salt, non-organic dairy, eggs, and freshwater fish Subclinical hypothyroidism; Vegans  Essential for production of thyroid hormones, fetal growth, skeletal and nervous system development; correcting deficiency can reduce the risk of miscarriage, stillbirth, goiter, or impaired cognitive development 
Choline 450 mg/d in pregnancy; 550 mg/day during lactation; 930 mg/d may provide additional benefit Eggs, beef, chicken, fish, dairy, cruciferous vegetables, leafy greens, beans, nuts, and seeds Vegans   Essential for brain development; impacts learning and memory 
Omega-3s  Minimum of 200 mg of DHA per day; 1-2g of EPA+DHA per day may offer additional benefit; no observed harmful effect with up to 2.7 g/d Salmon, herring, Atlantic mackerel, sardines, and rainbow trout; limited conversion of ALA from walnuts, flaxseed, and canola and soy oil Vegans Supplementation has been shown to increase birth weight, reduce the risk of preterm delivery, and improve short- and long-term neurodevelopment and visual acuity 


Nutritional intake in the preconception period and in pregnancy plays a crucial role in the developing child’s health. Given the needs of all future parents for high-quality preconception and perinatal care, naturopathic doctors are ideally situated to fill this important role. 


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Erica Nikiforuk, ND, RAc, is a licensed Naturopathic Doctor and Registered Acupuncturist in Ontario, Canada with a clinical focus on fertility, pregnancy, and perinatal health. She is a 2010 graduate of the Canadian College of Naturopathic Medicine (CCNM). Over the past decade, she has dedicated her practice to improving the health of current and future parents, thereby impacting generations to come. As an avid researcher, speaker, educator, and clinician, Dr. Erica remains up to date on the evidence-based use of nutrition for optimal health and pregnancy outcomes.  

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