Volume 17, No. 3, Summer 2009
By Jean Talbert, M.D.
Pregnant women are often advised to avoid certain foods to protect the health of their babies. As a result, these diets can become so restrictive that they no longer have adequate nutrition themselves. And good nutrition before and during pregnancy is a crucial component of a healthy pregnancy.
A well-balanced diet with appropriate weight gain can also decrease the risk of many pregnancy complications. What should pregnant women be eating or avoiding? Studies on pregnant women are limited but the risks and benefits of several nutrients are fairly well understood.
Folic acid, one of the B vitamins, is recognized as an essential nutrient pre-conception and during pregnancy. The risk of neural tube defects, such as spina bifida, is significantly reduced with adequate folic acid supplementation prior to conception and through the first trimester. Many cereals and breads are now fortified with folic acid, but it can also be found naturally in green leafy vegetables, citrus fruit, whole grains and beans. The current recommended intake for average risk women is 400 mcg per day, which is contained in most over-the-counter vitamins and all prenatal vitamins.
Calcium is important for bone health of both the mother and the fetus. Good calcium intakes have also been associated with higher birth weights and lower risk of preterm delivery. A calcium intake of 1000-1300 mg per day is currently recommended and supplements are advised if necessary.
Iron deficiency is not uncommon during pregnancy. A mild iron deficiency prior to pregnancy only becomes worse as the fetus depletes the mother’s iron stores. The CDC recommends 27 mg of iron per day for all pregnant women. This can be obtained through diet or vitamin supplements. Foods rich in iron include meat, dark green leafy vegetables, dried fruit, beans, nuts and blackstrap molasses. Iron absorption is improved if consumed with foods rich in vitamin C. Higher doses of iron are often advised during the third trimester.
Omega 3 fatty acids, the three types of which are EPA, DHA and ALA. Recent studies suggest that all three are important for the normal development of the fetal eyes and brain. They may also lower the risk of pre-eclampsia, preterm labor and post-partum depression. Many experts recommend approximately 300 mg per day of these omega 3 fatty acids. EPA and DHA are found primarily in oily fish. ALA is found in vegetable oils, seeds, leafy green vegetables, soy, walnuts or fortified foods such as eggs and orange juice. Some prenatal vitamins are now packaged with an additional capsule of flax seed or fish oil. Although shark, swordfish, king mackerel and tile fish are good dietary sources of omega 3 fatty acids, they should be avoided during pregnancy due to possible mercury contamination. Fish oil supplements derived from fish liver should also be avoided due to possible high vitamin A levels.
Vitamin A in excess levels has been associated with miscarriage and birth defects of the central nervous system, heart or face. Intake should not exceed 10,000 units per day. Vitamin A supplements in the form of beta-carotene or from foods such as leafy green vegetables, carrots, eggs, dairy products do not present any risk.
Fish may be a good source of omega 3 fatty acids, but excess consumption can introduce other risks, including high levels of mercury and should be completely avoided during pregnancy since mercury may cause central nervous system damage in fetuses. Otherwise, fish is a healthy food and pregnant women are advised to eat up to 12 oz of seafood such as salmon, pollack, catfish or shellfish per week or up to 6 oz of tuna per week. Canned light tuna is safer than albacore tuna or tuna steaks. The safety of local fresh water fish varies tremendously. Information can be obtained from the Environmental Protection Agency (www.epa.gov/waterscience/fish/states.htm or 1-888-SAFEFOOD). In addition, pregnant women should eat only cooked fish or frozen sushi grade raw fish to avoid infections with parasites or bacteria.
Peanut allergies have recently become more prevalent. But studies to date have shown no benefit of avoidance diets in the prevention of childhood allergies as some have claimed.
Artificial sweeteners have not been seen to increase the risk of birth defects. Nonetheless, pregnant women would probably benefit from natural food choices.
Foodborne infections present a particular risk to the fetus. For safety, follow these precautions:
Women of reproductive age should all be counseled regarding a healthy diet prior to conception. Visit www.mypyramid.gov to create an individualized diet plan for before and during pregnancy.
(Dr. Talbert is a board certified OB/GYN specialist practicing with Cape Obstetrics, Midwifery & Gynecology in Falmouth and Sandwich, 508-457-0088.)