Nutrition and pregnancy
Nutrition and pregnancy refers to the nutrient intake, and dietary planning that is undertaken before, during and after pregnancy. Nutrition of the fetus begins at conception. For this reason, the nutrition of the mother is important from before conception (probably several months before) as well as throughout pregnancy and breast feeding. An ever-increasing number of studies have shown that the nutrition of the mother will have an effect on the child, up to and including the risk for cancer, cardiovascular disease, hypertension and diabetes throughout life.
An inadequate or excessive amount of some nutrients may cause malformations or medical problems in the fetus, and neurological disorders and handicaps are a risk that is run by mothers who are malnourished. An estimated 24% of babies worldwide are born with lower than optimal weights at birth due to lack of proper nutrition. Personal habits such as consumption of alcohol or large amounts of caffeine can negatively and irreversibly affect the development of the baby, which happens in the early stages of pregnancy.
Caffeine consumption during pregnancy is associated with increased risk of pregnancy loss. The available research favors the notion that the benefits of fish consumption during pregnancy outweigh the risks; however, the type of fish is important. Folic acid, which is the synthetic form of the vitamin folate, is critical both in pre-and peri-conception.
Nutrition before pregnancy
As with most diets, there are chances of over-supplementing, however, as general advice, both state and medical recommendations are that mothers follow instructions listed on particular vitamin packaging as to the correct or recommended daily allowance (RDA). Daily prenatal use of iron substantially improves birth weight, potentially reducing the risk of Low birth weight.
- Folic acid supplementation is recommended prior to conception, to prevent development of spina bifida and other neural tube defects. It should be taken as at least 0.4 mg/day throughout the first trimester of pregnancy, 0.6 mg/day through the pregnancy, and 0.5 mg/day while breastfeeding in addition to eating foods rich in folic acid such as green leafy vegetables.
- Iodine levels are frequently too low in pregnant women, and iodine is necessary for normal thyroid function and mental development of the fetus, even cretinism. Pregnant women should take prenatal vitamins containing iodine.
- Vitamin D levels vary with exposure to sunlight. While it was assumed that supplementation was necessary only in areas of high latitudes, recent studies of Vitamin D levels throughout the United States and many other countries have shown a large number of women with low levels. For this reason, there is a growing movement to recommend supplementation with 1000 IU of Vitamin D daily throughout pregnancy.
- A large number of pregnant women have been found to have low levels of vitamin B12, but supplementation has not yet been shown to improve pregnancy outcome or the health of the newborn.
- Long-chain polyunsaturated fatty acids, specifically docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), are beneficial for fetal development. Several studies have shown lower risk of preterm delivery and low birth weight in mothers with higher intakes.
- Iron is needed for the healthy growth of the fetus and placenta, especially during the second and third trimesters. It is also essential before pregnancy for the production of hemoglobin.There is no evidence that a hemoglobin level of 7 grams/100 ml or higher is detrimental to pregnancy, but it must be acknowledged that maternal hemorrhage is a major source of maternal mortality worldwide, and a reserve capacity to carry oxygen is desirable. According to the Cochrane review conclusions iron supplementation reduces the risk of maternal anaemia and iron deficiency in pregnancy but the positive effect on other maternal and infant outcomes is less clear.
Nutrition during pregnancy
The United States and the European Union have established vitamin and mineral recommendations for during pregnancy and lactation. The amounts in the table below are the higher of the two. The citations separately list recommendations for pregnancy and lactation. Recommendations (RDAs = Recommended Dietary Allowances and PRIs = Population Reference Intakes) are set higher than what has been determined to be average requirements so as to address women who have above average needs. For some nutrients there is not enough information to set a recommendation, so the term Adequate Intake (AI) is used based on what appears to be sufficient.
|Nutrient||U.S. RDA or AI||EU PRI or AI||Unit|
|α-tocopherol (Vit E)||15||11*||mg|
|Thiamin (Vit B1)||1.2||1.0||mg|
|Riboflavin (Vit B2)||1.3||2.0||mg|
|Niacin (Vit B3)||16||16||mg|
|Pantothenic acid (Vit B5)||5*||7*||mg|
|Biotin (Vit B7)||30*||45*||µg|
|Folate (Vit B9)||400||600||µg|
|Cyanocobalamin (Vit B12)||2.4||5.0*||µg|
†Not established. EU has not identified an AI for sodium or chloride, and does not consider chromium to be an essential mineral nutrient.
Multiple micronutrient supplements taken with iron and folic acid can improve birth outcomes for women in low income countries. These supplements reduce numbers of low birth weight babies, small for gestational age babies and stillbirths in women who may not have many micronutrients in their usual diets. Undernourished women can benefit from having dietary education sessions and, balanced energy and protein supplements. A review showed that dietary education increased the mother’s protein intake and helped the baby grow more inside the womb. The balanced protein and energy supplement lowered risk of stillbirth and small babies and increased weight gain for both the mother and baby. Although more research is needed into the longer term effects on the mothers’ and infants’ health, the short term effects look promising.
Supplementing one's diet with foods rich in folic acid, fruits and dark green leafy vegetables helps to prevent neural tube birth defects in the fetus. In addition, prenatal vitamins typically contain increased amounts of folic acid, iodine, iron, vitamin A, vitamin D, zinc, and calcium over the amounts found in standard multi-vitamins. Zinc supplements have reduced preterm births by around 14% mainly in low income countries where zinc deficiency is common. However, the World Health Organisation does not routinely recommend zinc supplementation for all pregnant women.
For women with low calcium diets, taking calcium supplementation can reduce their risk of preeclampsia.[needs update] It has also been suggested that calcium can reduce numbers of births that happen before the 37th week of pregnancy (preterm birth). However a more recent review looking into other benefits of calcium supplementation did not find any improvement in numbers of preterm or low birth weight babies. There is not enough good quality to research to suggest best doses and timing of calcium supplementation.
Pregnant women are advised to pay attention to the foods they eat during pregnancy in order to reduce the risk of exposure to substances or bacteria that may be harmful to the developing fetus. This can include potentially harmful pathogens such as listeria, toxoplasmosis, and salmonella. Intake of large amounts of retinol has been linked to birth defects and abnormalities. Although seafood contains high levels of Omega-3 fatty acids which are beneficial for both mother and the baby, there is no consensus on consuming seafood during pregnancy. Pregnant women are advised to eat seafood in moderation.
During pregnancy, a woman's mass increases by about 12 kg (26 lb). The European Food Safety Authority recommends an increase of 300 mL per day compared to the normal intake for non-pregnant women, taking the total adequate water intake (from food and fluids) to 2,300 mL, or approximately 1,850 mL/ day from fluids alone
A mother's nutritional intake during pregnancy is believed to influence and possibly offer protective effects against the development of allergenic diseases and asthma in children. Maternal intake of vitamin D, vitamin E, and zinc have all been associated with a lower likelihood of wheezing in childhood, suggesting a protective effect. Additionally, maternal intake of omega-3 long chain polyunsaturated fatty acids (n-3 LC-PUFAs) has been associated with a reduced risk of development of eczema in childhood and reduced likelihood to for infants exhibit sensitivity to foods in the first year of life.
Caffeine consumption during pregnancy is associated with increased risk of pregnancy loss and increased risk of low birth weight, defined as below 2500 grams (5.5 pounds). The European Food Safety Authority and the American Congress of Obstetricians and Gynecologists concur that habitual caffeine consumption up to 200 mg per day by pregnant women does not give rise to safety concerns for the fetus. The United Kingdom Food Standards Agency had recommended that pregnant women should limit their caffeine intake to less than 300 mg of caffeine a day, but in 2009 revised that downward to less than 200 mg of caffeine a day.
Fetal alcohol spectrum disorders are a group of conditions that can occur in a person whose mother drank alcohol during pregnancy. The most severe form of the condition is known as fetal alcohol syndrome. Problems may include an abnormal appearance, short height, low body weight, small head size, poor coordination, low intelligence, behavior problems, hearing loss and vision problems. Those affected are more likely to have trouble in school, legal problems, participate in high-risk behaviors, and have trouble with alcohol and recreational drug use. Fetal alcohol syndrome usually occurs when a pregnant woman has more than four drinks per day. Milder symptoms have been found with two drinks per day during the early part of pregnancy. Evidence of harm from less than two drinks per day or 10 drinks per week is not clear.
The American Academy of Pediatrics established a conservative set of recommendations in 2015: "During pregnancy:no amount of alcohol intake should be considered safe; there is no safe trimester to drink alcohol; all forms of alcohol, such as beer, wine, and liquor, pose similar risk; and binge drinking poses dose-related risk to the developing fetus." The World Health Organization recommends that alcohol should be avoided entirely during pregnancy, given the relatively unknown effects of even small amounts of alcohol during pregnancy.
Fish and omega-3 fatty acids
Fish consumption during pregnancy is encouraged by European, Australian, and American guidelines. The reason given is that fat-containing fish such as salmon and tuna contain eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These are termed long chain, omega-3, polyunsaturated fatty acids, and are considered as important for fetal neurodevelopment. Additionally, fish are good sources of vitamins A, D, and B12, as well as the mineral iodine.
Due to risks of heavy-metal toxicity on fetal neurodevelopment, many mothers are concerned about eating fish during pregnancy. Overall, current research favors the notion that the benefits of fish consumption during pregnancy outweigh the risks; however, the type of fish is important. Current research suggests that 2-3 servings of low-methylmercury containing fish per week in pregnancy is both safe and beneficial. Mercury accumulates in fish through their own diet (bioaccumulation). A general rule of thumb is that fish higher up on the food chain, and with longer life spans will contain higher levels of mercury. Fish lower on the food chain and with shorter life spans will have lower metal content. However, it is important to note that the bioaccumulation of metals in fish is also dependent on geographical location, so it is hard to make global recommendations on specific fish species. An alternative to consuming fish is to use fish oil dietary supplements containing both EPA and DHA, or algae-derived DHA-only oils. The New York Times reported on a laboratory evaluation of 30 popular fish oil supplements. Some of those had less than the label claimed amounts of DHA. As for safety, "All of the products tested contained only very low levels of mercury, ranging from one to six parts per billion per serving. That range is far below the upper safety limit of 100 parts per billion set by the Global Organization for EPA and DHA Omega-3s, an industry trade group."
Folic acid, which is the synthetic form of the vitamin folate, is critical both in pre-and peri-conception. Deficiencies in folic acid may cause neural tube defects (NTDs). Women who had 0.4 mg of folic acid in their systems due to supplementing 3 months before childbirth significantly reduced the risk of NTDs. More than 80 countries use fortification of certain foods with folic acid as a measure to decrease the rate of NTDs.
Vitamins C and E
The combination of vitamin E and vitamin C supplemented to pregnant women does not appear to be efficacious for reducing risk of stillbirth, neonatal death, preterm birth, preeclampsia or any other maternal or infant outcomes, either in healthy women or those considered at risk for pregnancy complications. Antioxidant vitamins as dietary supplements had been proposed as having benefits if consumed during pregnancy. For the combination of vitamin E with vitamin C supplemented to pregnant women, a Cochrane review of 21 clinical trials concluded that the data do not support vitamin E supplementation - majority of trials alpha-tocopherol at 400 IU/day plus vitamin C at 1000 mg/day - as being efficacious for reducing risk of stillbirth, neonatal death, preterm birth, preeclampsia or any other maternal or infant outcomes, either in healthy women or those considered at risk for pregnancy complications. The review identified only three small trials in which vitamin E was supplemented without co-supplementation with vitamin C. None of these trials reported any clinically meaningful information. A second Cochrane review of 29 trials, published same year, reported on the same combination trials but added analysis of trials with vitamin C alone. The conclusion was that the data do not support routine vitamin C supplementation alone or in combination with other supplements for the prevention of fetal or neonatal death, poor fetal growth, preterm birth or preeclampsia.
Nutrition after pregnancy
Proper nutrition is important after delivery to help the mother recover, and to provide enough food energy and nutrients for a woman to breastfeed her child. Women having serum ferritin less than 70 µg/L may need iron supplements to prevent iron deficiency anaemia during pregnancy and postpartum.
During lactation, water intake may need to be increased. Human milk is made of 88% water, and the IOM recommends that breastfeeding women increase their water intake by about 300 mL/day to a total volume of 3000 mL/day (from food and drink); approximately 2,400 mL/day from fluids.
- Barasi EM (2003). Human Nutrition - A Health Perspective. London: Arnold. ISBN 978-0-340-81025-5.
- "WHO | 10 facts on nutrition". World Health Organization. 2011-03-15. Retrieved 2011-08-07.
- Riley L (2006). Pregnancy: The Ultimate Week-by-Week Pregnancy Guide. Meredith Books. pp. 21–22. ISBN 978-0-696-22221-4.
- Chen LW, Wu Y, Neelakantan N, Chong MF, Pan A, van Dam RM (2016). "Maternal caffeine intake during pregnancy and risk of pregnancy loss: a categorical and dose-response meta-analysis of prospective studies". Public Health Nutr. 19 (7): 1233–1244. doi:10.1017/S1368980015002463. PMID 26329421.
- Starling, Phoebe; Charlton, Karen; McMahon, Anne T.; Lucas, Catherine (2015-03-18). "Fish Intake during Pregnancy and Foetal Neurodevelopment—A Systematic Review of the Evidence". Nutrients. 7 (3): 2001–2014. doi:10.3390/nu7032001. PMC 4377896. PMID 25793632.
- Williamson CS (2006). "Nutrition in pregnancy". British Nutrition Foundation. 31: 28–59. doi:10.1111/j.1467-3010.2006.00541.x.
- Haider, BA, Olofin, I, Wang, M; et al. (2013). "Anaemia, prenatal iron use, and risk of adverse pregnancy outcomes: systematic review and meta-analysis". British Medical Journal. 21: f3443. doi:10.1136/bmj.f3443. PMC 3689887. PMID 23794316.CS1 maint: Multiple names: authors list (link)
- Schaefer, Christof (2001). Drugs During Pregnancy and Lactation: Handbook of Prescription Drugs and Comparative Risk Assessment. Gulf Professional Publishing. ISBN 9780444507631. Retrieved 2015-05-13.
- Shils, Maurice Edward; Shike, Moshe (2006). Modern Nutrition in Health and Disease. Lippincott Williams & Wilkins. ISBN 9780781741330. Retrieved 2015-05-13.
- Aghajafari, Fariba; Nagulesapillai, Tharsiya; Ronksley, Paul E.; Tough, Suzanne C.; O'Beirne, Maeve; Rabi, Doreen M. (2013). "Association between maternal serum 25-hydroxyvitamin D level and pregnancy and neonatal outcomes: systematic review and meta-analysis of observational studies". BMJ (Clinical Research Ed.). 346: f1169. doi:10.1136/bmj.f1169. ISSN 1756-1833. PMID 23533188.
- Briggs, Gerald G.; Freeman, Roger K.; Yaffe, Sumner J. (2011). Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk. Lippincott Williams & Wilkins. ISBN 9781608317080. Retrieved 2015-05-13.
- Imhoff-Kunsch, Beth; Briggs, Virginia; Goldenberg, Tamar; Ramakrishnan, Usha (Jul 2012). "Effect of n-3 long-chain polyunsaturated fatty acid intake during pregnancy on maternal, infant, and child health outcomes: a systematic review". Paediatric and Perinatal Epidemiology. 26 Suppl 1: 91–107. doi:10.1111/j.1365-3016.2012.01292.x. ISSN 1365-3016. PMID 22742604.
- Jensen, CL (Jun 2006). "Effects of n-3 fatty acids during pregnancy and lactation". The American Journal of Clinical Nutrition. 83 (6 Suppl): 1452S–1457S. doi:10.1093/ajcn/83.6.1452S. ISSN 0002-9165. PMID 16841854.
- Peña-Rosas, Juan Pablo; De-Regil, Luz Maria; Garcia-Casal, Maria N.; Dowswell, Therese (2015-07-22). "Daily oral iron supplementation during pregnancy". The Cochrane Database of Systematic Reviews (7): CD004736. doi:10.1002/14651858.CD004736.pub5. ISSN 1469-493X. PMC 4233117. PMID 26198451.
- "Dietary Reference Intakes (DRIs)" (PDF). Food and Nutrition Board, Institute of Medicine, National Academies. Retrieved 24 August 2017.
- "Overview on Dietary Reference Values for the EU population as derived by the EFSA Panel on Dietetic Products, Nutrition and Allergies" (PDF). 2017. Archived (PDF) from the original on August 28, 2017.
- Haider, Batool A.; Bhutta, Zulfiqar A. (2017). "Multiple-micronutrient supplementation for women during pregnancy". The Cochrane Database of Systematic Reviews. 4: CD004905. doi:10.1002/14651858.CD004905.pub5. ISSN 1469-493X. PMID 28407219.
- Ota, E; Hori, H; Mori, R; Tobe-Gai, R; Farrar, D (2 June 2015). "Antenatal dietary education and supplementation to increase energy and protein intake". The Cochrane Database of Systematic Reviews. 6 (6): CD000032. doi:10.1002/14651858.CD000032.pub3. PMID 26031211.
- Ota, E; Mori, R; Middleton, P; Tobe-Gai, R; Mahomed, K; Miyazaki, C; Bhutta, ZA (2 February 2015). "Zinc supplementation for improving pregnancy and infant outcome". The Cochrane Database of Systematic Reviews. 2 (2): CD000230. doi:10.1002/14651858.CD000230.pub5. PMID 25927101.
- "Zinc supplementation during pregnancy". World Health Organization. Retrieved 22 April 2016.
- Hofmeyr, GJ; Lawrie, TA; Atallah, AN; Duley, L; Torloni, MR (24 June 2014). "Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems". The Cochrane Database of Systematic Reviews. 6 (6): CD001059. doi:10.1002/14651858.CD001059.pub4. PMID 24960615.
- Buppasiri, P; Lumbiganon, P; Thinkhamrop, J; Ngamjarus, C; Laopaiboon, M; Medley, N (25 February 2015). "Calcium supplementation (other than for preventing or treating hypertension) for improving pregnancy and infant outcomes". The Cochrane Database of Systematic Reviews. 2 (2): CD007079. doi:10.1002/14651858.CD007079.pub3. PMID 25922862.
- "Vitamin A (retinol)". Drugs and Supplements. Mayo Clinic. November 1, 2013. Retrieved May 17, 2015.
- "11 Weeks Pregnant – Symptoms, Growth, Tips | Pregnancy Savvy". www.pregnancysavvy.com. Retrieved 2016-08-04.
- Water Institute of Medicine Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: National Academies Press (2004).
- EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA) (2010). "Scientific Opinion on Dietary reference values for water". EFSA Journal. 8 (3): 1459–1507. doi:10.2903/j.efsa.2010.1459.CS1 maint: Multiple names: authors list (link)
- Beckhaus AA, Garcia-Marcos L, Forno E, Pacheco-Gonzalez RM, Celedón JC, Castro-Rodriguez JA (2015). "Maternal nutrition during pregnancy and risk of asthma, wheeze, and atopic diseases during childhood: a systematic review and meta-analysis". Allergy. 70 (12): 1588–1604. doi:10.1111/all.12729. PMID 26296633.
- Best, Karen P.; Gold, Michael; Kennedy, Declan; Martin, James; Makrides, Maria (January 2016). "Omega-3 long-chain PUFA intake during pregnancy and allergic disease outcomes in the offspring: a systematic review and meta-analysis of observational studies and randomized controlled trials". The American Journal of Clinical Nutrition. 103 (1): 128–143. doi:10.3945/ajcn.115.111104. ISSN 1938-3207. PMID 26675770.
- Li J, Zhao H, Song JM, Zhang J, Tang YL, Xin CM (2015). "A meta-analysis of risk of pregnancy loss and caffeine and coffee consumption during pregnancy". Int J Gynaecol Obstet. 130 (2): 116–122. doi:10.1016/j.ijgo.2015.03.033. PMID 26026343.
- Rhee J, Kim R, Kim Y, Tam M, Lai Y, Keum N, Oldenburg CE (2015). "Maternal Caffeine Consumption during Pregnancy and Risk of Low Birth Weight: A Dose-Response Meta-Analysis of Observational Studies". PLoS ONE. 10 (7): e0132334. doi:10.1371/journal.pone.0132334. PMC 4507998. PMID 26193706.
- Chen LW, Wu Y, Neelakantan N, Chong MF, Pan A, van Dam RM (2014). "Maternal caffeine intake during pregnancy is associated with risk of low birth weight: a systematic review and dose-response meta-analysis". BMC Med. 12: 174. doi:10.1186/s12916-014-0174-6. PMC 4198801. PMID 25238871.
- EFSA Journal 2015;13(5):4102 Scientific Opinion on the safety of caffeine European Food Safety Authority (2015).
- American College of Obstetricians and Gynecologists (August 2010). "ACOG CommitteeOpinion No. 462: Moderate caffeine consumption during pregnancy". Obstetrics and Gynecology. 116 (2 Pt 1): 467–468. doi:10.1097/AOG.0b013e3181eeb2a1. PMID 20664420.
- "Food Standards Agency publishes new caffeine advice for pregnant women". Retrieved 3 August 2009.
- "Facts about FASDs". 16 April 2015. Archived from the original on 23 May 2015. Retrieved 10 June 2015.
- Coriale, G; Fiorentino, D; Di Lauro, F; Marchitelli, R; Scalese, B; Fiore, M; Maviglia, M; Ceccanti, M (2013). "Fetal Alcohol Spectrum Disorder (FASD): neurobehavioral profile, indications for diagnosis and treatment". Rivista di Psichiatria. 48 (5): 359–369. doi:10.1708/1356.15062. PMID 24326748.
- Yaffe, Sumner J. (2011). Drugs in pregnancy and lactation : a reference guide to fetal and neonatal risk (9 ed.). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. p. 527. ISBN 9781608317080. Archived from the original on 10 September 2017.
- "Pregnancy and alcohol: occasional, light drinking may be safe". Prescrire Int. 21 (124): 44–50. Feb 2012. PMID 22413723.
- Henderson, J; Gray, R; Brocklehurst, P (March 2007). "Systematic review of effects of low-moderate prenatal alcohol exposure on pregnancy outcome". BJOG : An International Journal of Obstetrics and Gynaecology. 114 (3): 243–252. doi:10.1111/j.1471-0528.2006.01163.x. PMID 17233797.
- Williams JF, Smith VC (2015). "Fetal Alcohol Spectrum Disorders". Pediatrics. 136 (5): e1395–e1406. doi:10.1542/peds.2015-3113. PMID 26482673.
- "Framework for alcohol policy in the WHO European Region" (PDF). World Health Organisation.
- EFSA Dietetic Products, Nutrition, and Allergies (NDA) (2014-07-01). "Scientific Opinion on health benefits of seafood (fish and shellfish) consumption in relation to health risks associated with exposure to methylmercury". EFSA Journal. 12 (7): n/a. doi:10.2903/j.efsa.2014.3761. ISSN 1831-4732.
- Council, National Health and Medical Research (2013-02-07). "Australian Dietary Guidelines (2013) | National Health and Medical Research Council". Retrieved 2018-01-22.
- "2015-2020 Dietary Guidelines - health.gov". health.gov. Retrieved 2018-01-22.
- Bosch, Adina C; O'Neill, Bernadette; Sigge, Gunnar O; Kerwath, Sven E; Hoffman, Louwrens C (2016-01-15). "Heavy metals in marine fish meat and consumer health: a review". Journal of the Science of Food and Agriculture. 96 (1): 32–48. doi:10.1002/jsfa.7360. ISSN 1097-0010. PMID 26238481.
- Conner, Anahad (22 January 2014). "What's in Your Fish Oil Supplements?". The New York Times. Retrieved 7 November 2018.
- "Recommendations | Folic Acid | NCBDDD | CDC". www.cdc.gov. Retrieved 2015-05-13.
- Wald NJ, Morris JK, Blakemore C (2018). "Public health failure in the prevention of neural tube defects: time to abandon the tolerable upper intake level of folate". Public Health Rev. 39: 2. doi:10.1186/s40985-018-0079-6. PMC 5809909. PMID 29450103.
- Rumbold A, Ota E, Hori H, Miyazaki C, Crowther CA (September 2015). "Vitamin E supplementation in pregnancy". Cochrane Database Syst Rev (9): CD004069. doi:10.1002/14651858.CD004069.pub3. PMID 26343254.
- Rumbold A, Ota E, Nagata C, Shahrook S, Crowther CA (September 2015). "Vitamin C supplementation in pregnancy". Cochrane Database Syst Rev (9): CD004072. doi:10.1002/14651858.CD004072.pub3. PMID 26415762.
- Milman N, Byg KE, Bergholt T, Eriksen L, Hvas AM (2006). "Body iron and individual iron prophylaxis in pregnancy--should the iron dose be adjusted according to serum ferritin?". Ann. Hematol. 85 (9): 567–573. doi:10.1007/s00277-006-0141-1. PMID 16733739.
- Sethi V, Kapil U (2004). "Iodine deficiency and development of brain". Indian J Pediatr. 71 (4): 325–9. doi:10.1007/BF02724099. PMID 15107513.
- "Nutrition During Pregnancy Resource List for Consumers" (PDF). USDA NAL Food and Nutrition Information Center.
- Health Education Authority (1996) Folic acid - what all women should know (leaflet) London:HEA