Healthy Mother Healthy Infant Through Nutrition
WHEC Practice Bulletin and Clinical Management Guidelines for healthcare providers. Educational grant provided by Women's Health and Education Center (WHEC).
Maternal nutritional status not only influences fetal development and overall health but also significantly affects long-term risk for chronic childhood and adult diseases. Many pregnant and lactating women may not achieve optimum levels of important nutrients, as evidenced by the proportion of women throughout the US population and in the world, whose nutritional levels do not meet documented standards for many vitamins, minerals, and other essential nutrients. Clinicians should counsel all pregnant women about the importance of good dietary habits. At the same time, vitamin and nutrient supplements, particularly prescription products regulated by the US Food and Drug Administration (FDA) for quality and accuracy in labeling, should also be considered as a strategy to improve maternal nutrition and help lead to healthy outcomes for their offsprings. Nowadays, the pregnant patients eat a wider variety of foods, including more imported products and foods prepared outside the home. Food imports are up by 35%, to 48 million metric tons, over the past decade. Although imports now comprise roughly 15% of US diet, the percentages of imports in some food categories are much higher. In 2009, 55% of tree nuts and 85% of fish and seafood eaten were imported. The safety of imported foods has raised concerns, especially because more of the inherently high-risk foods (ready-to-eat food, fresh produce, and seafood) are imported. However, by recent estimates, the US Department of Agriculture (USDA) physically examines only 10% of imported meat and poultry, and 4% of the import gets microbial testing. The FDA (responsible for most other food and drink) estimates it physically examines or tests only 1% of food imports.
The purpose of this document is to review the importance of optimizing nutritional intake during preconception, pregnancy and lactation. Women's Health and Education Center (WHEC) places emphasis on specific nutrients essential for optimal fetal development, notably folic acid, calcium, vitamin D, and omega-3 fatty acids; these are often consumed at levels below the recommended requirements. Maternal/infant morbidity and mortality are age-old and worldwide problems. There are many factors that influence the ultimate outcome of pregnancy, including the absence or presence of access to prenatal care, maternal stress (physical and psychological), comorbid diseases, and maternal nutrition -- both before and during pregnancy. Good nutrition is much more than just the food we eat.
Common Nutrition Terms:
There can be confusion over the definition of some terms used in discussions of nutrition. Here are some definitions of terms commonly used:
Importance Of Nutrition Throughout A Woman's Life:
Maintaining adequate nutritional status is essential for women throughout all stages of their lives:
Nutritional Requirements And Fetal Development:
Optimal nutritional status is essential prior to and after conception. Although genetically determined cellular and tissue development provide the framework for fetal growth pathways, suboptimal maternal nutrition status during preconception and pregnancy can lead to intrauterine growth restriction (IUGR), correlates with long-term functional deficits, and increases risk for chronic childhood and adult disease. Clearly optimal maternal nutrition is essential for both fetal well-being and an individual's long-term physical and mental development. Nutrient requirements unique to the gestational period include an approximately 50% increase in the need for protein, iron, folic acid, and vitamin B6, compared with preconception requirements. Women should increase consumption of macronutrient calories, proteins, carbohydrates, essential fatty acids, minerals (eg, calcium, zinc, iron), vitamins (eg, D, B series, C) and micronutrients (choline, phytonutrients) during gestation. During gestation and early infancy, organ and nervous systems are both "grown" and "programmed." The effects of both adverse and beneficial conditions may affect the anatomy, physiology, and metabolism of the growing child. Nutritional deficiency during gestation has been linked to cell programming of long-term "memory', leading to insulin resistance. Originally, such changes in physiologic set points, organ size, and cell-signaling programming were termed "functional teratogenesis."
Essential fatty acids (EFAs) -- docosahexaenoic acid (DHA) are low in North American diets. Suboptimum levels of EFAs have been suggested to delay fetal neurovascular development and lead to pre- and postnatal deficits in preterm infants. A well-established relationship has been shown between maternal folic acid deficiency and infant neural tube defects (NTDs), such as spina bifida and anencephaly. Periconceptional intake of folic acid supplements reduces the rate of NTDs by as much as 80% and also decreases recurrence risk in subsequent births. United States Public Health Service recommends all women of childbearing age consume at least 0.4 mg (400 mcg) of folic acid daily to reduce the risk of NTDs. The Institute of Medicine (IOM) recommends consumption of folic acid at 600 mcg/day for adult women aged 19 years and older; and 800 mcg daily for adolescents aged 14 to 18 years. Importantly 3 months of folic acid supplementation is required to achieve steady-state folic acid levels. Fetal neural tube closure is complete by approximately 24 days post-conception; therefore, supplementation with folic acid should precede conception. If folic acid consumption begins at the first prenatal visit, NTDs will not be reliably prevented. At a minimum, women who fail to meet the daily dietary folic acid supplementation between 4 to 8 weeks prior to conception. Currently available prenatal formulations containing 1 mg folic acid have become a standard component of obstetric care. As a result of these initiatives, the rate of NTDs has dropped from 78% to 31%.
Calcium and vitamin D are essential for fetal skeletal development and organization. Insufficient maternal dietary calcium and vitamin D inhibit childhood mineral accrual. Vitamin D is necessary for the absorption of calcium. Dietary supplementation with vitamin D during pregnancy increases fetal calcium and vitamin D levels and enhances childhood bone mass. The National Institutes of Health US Office of Dietary Supplements recommends that pregnant women receive calcium, 1,300 mg daily, and vitamin D 200 IU daily. Prenatal vitamins contain calcium 400 to 800 mg, plus recommended amounts of vitamin D.
Potential benefits of polyunsaturated fatty acids (PUFAs): These important substances take several forms, n-6 and n-3 PUFAs are essential dietary nutrients that cross the placenta to contribute to brain, central nervous system, and other organ development in growing fetus. Besides their role in fetal neural development, omega-3 fatty acids may help lower the risk of hypertension, arteriosclerosis, coronary artery disease, and stroke. The last trimester of pregnancy and month after birth feature substantial increases in brain levels of the long-chain omega-3 fatty acid DHA and the long-chain omega-6 PUFA AA. DHA promotes neural stem cell differentiation into neurons by prompting cell cycle exit and suppressing cell death. In cell membranes, DHA affects the function of multiple brain and non-brain cell membrane proteins and receptors, as well as neurotransmitter levels and gene expression. In the newborn, levels are closely correlated with maternal long-chain PUFA status. Preterm infants have relatively low levels of both DHA and AA in brain tissue caused by a shortened period of exposure to maternal DHA. After birth, infants require additional PUFA for optimal development. Both human milk and fortified formula provide DHA. Fish, meat, poultry, eggs, and DHA-enriched foods can also be a source of DHA for pregnant women. Evidence indicates that the typical US diet contains only 100 to 200 mg/d of the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The Workshop on the Essentiality of and Recommended Dietary Intakes for Omega-6 and Omega-3 Fatty Acids advise that pregnant and lactating women consume at least 300 mg of DHA/EPA daily; the recommended amount for men and non-pregnant women is 220 mg daily.
Iron Requirements During Pregnancy:
Appropriate intake of iron during the first two trimesters of pregnancy improves a woman's ability to carry her infant to term, and to deliver a baby of normal weight. It also helps protect against iron deficiency anemia (hemoglobin <11 g/dL), a condition that can contribute to development delays and behavioral disturbances in infants and poor health in the mother. Data from the complete National Health and Nutrition Examination Survey III indicated that 11% of nonpregnant women aged 16 to 49 years had iron deficiency, and that 3% to 5% also had iron-deficiency anemia. Regrettably, comparable data for US population of all pregnant women are unavailable. Given the low dietary intake of iron among US women of childbearing age and the increased demand for iron during pregnancy, iron supplementation is a consideration for many expectant mothers.
The normal iron requirement for adult women who are not pregnant is 18 mg/day. During pregnancy, iron requirements increase to 27 mg/day, driven by several unique conditions:
A demand this large cannot be met through the average US diet, which typically contains around 15 mg/day of iron, or by existing iron stores. The Centers for Disease Control and Prevention (CDC), American Academy of Pediatrics (AAP) and American College of Obstetricians and Gynecologists (ACOG) therefore recommend universal iron supplementation to meet iron requirements during pregnancy, and to help prevent anemia in both mother and infant. IOM and ACOG recommend 27 (RDA), 45 (UL) mg/day, and CDC recommendation is 30 mg/day. One word of caution with respect to iron supplementation: because iron can accumulate in the tissues, causing organ damage, supplementation must be planned carefully. Finding the right amount of iron is a balancing act that encompasses such considerations as iron stores, maternal/fetal demand, gastrointestinal absorption, and iron formulation. The IOM has set the tolerable UL for iron at 45 mg/day.
Iron: Risk/Benefit Ratio of Achieving Nutritional Adequacy
Risks: 1) Deficient iron intake predisposes a woman to anemia and poor pregnancy outcomes, 2) Iron overload can lead to potentially dangerous accumulation of iron in vital organs (liver, heart), bleeding disorders, toxicity, and secondary hemochromatosis.
Benefits: Appropriate intake improves maternal and fetal outcomes, including pregnancy mortality.
When planning iron supplementation, the type or iron given is just as important a consideration as the amount. This is because absorption of iron varies considerably between preparations. Note these examples:
Newer forms of iron supplements tend to be better absorbed and better tolerated. For example, chelated iron has a much higher bioavailability than ferrous sulfate. Many studies have found that the absorption of iron from a chelated iron is 4 times higher than that from ferrous sulfate. The RDA of iron is calculated by determining the amount of iron required (ie, the amount that needs to be absorbed) to meet the needs of most women and then estimating the amount of iron in a mixed diet that will be absorbed. For pregnant women, absorption is calculated as 25% during the second and third trimesters. The 27 mg/day requirement during pregnancy is the amount of iron that needs to be obtained from a mixed diet to ensure that the mother is able to absorb enough iron to meet her daily requirement of 25% during pregnancy. The formulation of iron also affects tolerance, which along with safety, is a big concern during pregnancy. Some iron preparations can aggravate such gastrointestinal disturbances of pregnancy as nausea and constipation, detracting from compliance. Chelated forms of iron tend to be better absorbed and better tolerated than ferrous sulfate.
Nutritional Goals And Management:
Typically, women consuming three meals a day including fruits and vegetables, low-fat proteins, and low saturated fats have appropriate servings of essential nutrients. However, women who frequently skip meals or have a high intake of soft drinks, fast foods, and snacks are often deficient in nutrients and benefit from nutritional counseling. Women should aim to:
Special Nutritional Recommendations in Pregnancy:
Nutritional Goals And Weight Management:
Weight gain guidelines were modified in 2009 by the Institute of Medicine (IOM). The guidelines had not been revised in nearly two decades. Now, a different population of women is carrying pregnancies. American mothers now tend to be older, have higher frequency of multiples, higher pregnancy BMI, and higher burden of chronic diseases. Achieving a normal BMI prior to conception improves general health maintenance, mental health, and energy as a new parent. Nearly all complications of pregnancy are increased in obese women. Morbidly obese women (BMI >35) are more likely to develop gestational hypertension, preeclampsia, and gestational diabetes and to have increased risk for preterm delivery, macrosomic infants (>4,500 g), and cesarean delivery. Obese women also have greater long-term health risks, such as cardio-vascular disease, as they age. Obesity carries an increased risk not only for the parturient but also for her child. Maternal obesity in the first trimester of pregnancy is associated with elevated risk for having an overweight child. Weight reduction is not recommended during pregnancy.
Calorie And Micronutrient Changes:
Calories are the most important factor in nutrition correlated with infant birth weight; yet, the relationship between maternal calories consumed, weight gained, and infant birth weight is complex. Pregnant women are recommended to increase daily calorie intake by 340 kcal/day in the second trimester and 452 kcal/day in the third trimester. However, calorie requirements vary by current weight and energy expenditure. Diets low in cholesterol and saturated fats are preferred and have been associated with decreased risk for preterm delivery.Trans fatty acids are transported across the placenta and may affect essential fatty acid metabolism, adversely impacting fetal growth and development. "My Pyramid for Moms" from the United States Department of Agriculture (USDA) offers assistance with food selection (see the link below). The IOM and Centers for Disease Control and Prevention (CDC) recommend that pregnant women who do not consume adequate, balanced diet supplement it with prenatal vitamins containing iron and folic acid. Iron deficiency anemia is common in pregnancy, especially in women with poor nutritional habits.
Micronutrient Alterations in Pregnancy:
Recommended daily allowances (RDAs) of nutrients are different in females of different ages and during pregnancy and lactation. Micronutrients do not have profound effects on fetal birth weight in well-nourished women, with few exceptions. In prospective studies in Tanzania, women receiving prenatal vitamins had lower rates of small-for-gestational-age infants, while rates of preterm delivery were not statistically different.
Dietary Modifications During Pregnancy
Omega-3 fatty acids, found in fish and shell-fish, have a beneficial effect on maternal health and fetal neurodevelopment. Conversely, diets high in mercury-containing fish can have teratogenic effects. Following initial reports in the 1960s correlating elevated maternal mercury levels with teratogenicity, there have been several longitudinal cohort studies investigating this relationship. These studies yield conflicting results. Overall, significantly elevated mercury levels have adverse effects on the fetal central nervous system; conversely avoidance of fish yields lower maternal and fetal health benefits. Predatory and older fish contain higher levels of mercury. These fish include shark, mackerel, tile fish, and marlin. Commonly consumed fish with lower levels of mercury are shrimp, canned light tuna, salmon, pollack, and catfish. Albacore tuna has more mercury than canned light tuna, and therefore consumption should be limited to once weekly. Most fish consumers are unlikely to be at risk regarding exposure to methyl-mercury provided their consumption of fish with higher mercury content is less than once per week. The Environmental Protection Agency and local health departments provide information regarding safety of fish consumption in local areas. More information can be found at www.who.int/foodsafety/publications/chem/mercury
Exposure recommendations for fish consumption are:
The problem with fish is not only mercury, but other poisons as well, although contamination levels have declined over recent decades. Prenatal exposure to PCBs and dioxins has been linked to neurologic deficits in children. Both farmed and wild salmon can contain PCBs, but freshwater fish are worse, especially those from the Great Lakes. Eating wild rather than farmed salmon has been controversial. Research shows that farmed Atlantic salmon is higher in contaminants (PCBs, dioxins, polybrominated diphenyl ethers [PBDEs], and some pesticides) than wild Pacific salmon, but it also contains higher levels of omega-3 than wild Pacific salmon. Researchers have stated that the benefit (lives saved by preventing coronary disease) from North and South American farmed sources outweighs the risk (lives lost from cancer) and is on par with the wild sources. Caviar and brains are particularly high in DHA. We advise patients to lessen their risk by choosing smaller fish, handling and cooking fish carefully, and staying away from raw fish or seafood.
Nutrient-rich liver can be eaten during pregnancy. Despite concern by some that a high intake of preformed vitamin A from supplements or liver (>15,000 IUs per day) could be teratogenic, other have questioned the threshold. Beta-carotene, found in fruits and vegetables, is not of concern. Although it may not be necessary, we suggest that our patients avoid large amounts of liver (also liverwurst, Braunschweiger, or pâté) during their first trimester.
The safety of consuming caffeine during pregnancy continues to raise questions. There seems to be no increased risk of birth defects associated with caffeine. Lowering a prenatal patient's intake does not necessarily improve birth weight or length of gestation. The consumption of caffeine in pregnancy has been historically linked with increased rates of miscarriage and low birth weight. Data are not conclusive and at best are fraught with numerous confounders, including drink serving size, brand of coffee, tea, or soda, and brewing method. One recent randomized trial gave pregnant women either caffeinated or decaffeinated coffee starting at 20 weeks of gestation. Average birth weight and length of gestation were similar in both groups, discounting the correlation with low birth weight. Because data are limited, current recommendations are conservative and suggest limiting caffeine intake to less than 300 mg/day. We suggest expectant mothers limit their coffee to 2 cups per day (or switch to decaf) and add lots of milk.
Abstaining From Alcohol:
It is well known that high intake of alcohol during pregnancy causes fetal alcohol syndrome (FAS). Heavy drinking (defined as 1 or more drinks per day) has been associated with a 5-fold increased risk of low birth weight and double the risk of preterm delivery, and the cognitive and behavioral deficits seen with moderate intake can affect school performance. Problems appear to be more severe with bingeing or getting drunk for older mothers and for those in poor health or who smoke or use drugs. However, susceptibility also varies, and no safe threshold has been identified. For this reason, ACOG, citing the Surgeon General, the AAP, and the CDC, recommends abstinence during pregnancy as well as periconceptually. Even brief interventions can be effective in helping a mother reduce her alcohol use. Cautiously, reassure a worried mother who has taken only a few drinks during early pregnancy that stopping now should the likelihood of a healthy baby.
There are many artificial sweeteners available on the market. To date, none are associated with an increased risk of birth defects above the base-line rate in the general population. Sweeteners evaluated include aspartame (NutraSweet®), sucralose (Splenda®), saccharin (Sweet'N Low®), acesulfame potassium (Sunett®), and stevioside (Stevia). Consistent with most dietary recommendations, artificial sweeteners should be used in moderation during pregnancy. Despite limited research, FDA says acesulfame-K (Sunett, Sweet One), neotame, and sucralose (Splenda) are safe in moderation. Aspartame (Equal, NutraSweet), although safe in moderation for most, is not safe for anyone with phenylketonuria (PKU), because it contains phenylalanine. Saccharine (Sweet 'N Low) is of concern during pregnancy because it crosses the placenta and could accumulate in fetal tissue because of slow fetal clearance. However, the National Toxicology Program has taken it off the list of human carcinogens. Practically speaking, because artificial sweeteners are often found in foods with few other nutrients, they often need to be limited so that they do not displace more valuable, nutrient-dense foods.
Nitrates versus Nitrites:
Nitrates and nitrites raise two concerns. The biggest worry is contaminated water causing infant methemoglobinemia. Both inorganic (fertilizers, airborne emissions) and organic (sewage, manure) nitrates migrate to groundwater. Nitrogen in the water is taken up by plants, and we get perhaps more than 70% of our dietary nitrates from vegetables. Those with the most nitrates include cauliflower, spinach, collards, broccoli and root vegetables. Nitrates are not considered toxic. They may even be beneficial by enhancing host defenses. However, some nitrates are converted to nitrites, which may combine with hemoglobin to form methemogobin, a process that happens more readily in fetal hemoglobin. Well water should be tested for nitrate contamination before used to make infant formula. Nitrates, nitrites, andN- nitroso compounds can cross the placenta, and expectant mother and the fetus may be more sensitive to the insult at around 30 weeks. Some studies have raised concerns that high nitrate consumption could be linked to anemia, preeclampsia, IUGR, premature labor, sterility, miscarriages, and neural tube defects. However, there are many problems with the studies, and they seem to lack sufficient evidence to say the relationship is casual. The second key issue concerns nitrates and nitrites in processed meats (lunch meats, hot dogs, bacon, and ham) forming nitrosamines, raising the risk of cancers. The most important reason that nitrites are added to cured and smoked meats is to reduce the risk of botulism. Nitrite concentrations in cured meats have gone down in the last 30 years, and antioxidants have been added, both with the goal of lowering the formation ofN-nitroso compounds. The link with cancer seems to be even less likely now.
Herbs and Dietary Supplements:
Herbal supplements during pregnancy merit attention. Many have not been tested during pregnancy and lactation, so our suggestion is to advise caution. Foods made with herbs pose little risk, but the dose is much higher in dietary supplements, and there is also the issue of lack of oversight of their content, effectiveness, and safety. Advise patients to treat herbal remedies with the same respect as drugs and to be aware of possible interactions. Some herbs of particular concern during pregnancy may include flax oil (possible risk of preterm labor), devil's claw (oxytocin effects), schizandra (uterine stimulant), licorice (abortifacient, estrogenic effects, uterine stimulant), papain (teratogenic, embryotoxic), black cohosh (uterine stimulant), blue cohosh (uterine stimulant, potentially teratogenic, toxicity in infant), oral aloe (latex may induce abortion), green tea (large amounts -- high caffeine, possible anti-folate activity), and sida cordifolia (ephedrine constituent).
The process of optimizing a childbearing woman's nutritional intake should begin preconceptionally. Taking steps to eat properly and to control weight, blood pressure, and blood sugar levels before conceiving improves a woman's chances for a smooth, successful pregnancy with a good outcome. Several key nutrients in the diet of pregnant women need attention for optimal fetal development (eg, folic acid, calcium, essential fatty acids). The lack of appropriate nutrition can have long-term effects and is clearly preventable. Published data support the role of essential fatty acids in fetal development. A balanced diet, including proper amounts of macro- and micro-nutrients, is critical in the early development of the prenatal brain; yet available research suggests that most American women are not reaching the recommended daily requirements for many nutrients from their usual daily diets. Low intake of vitamin D and calcium, folic acid, iron and omega-3 fatty acids is common and should be addressed. However, the challenges to reaching appropriate goals, due to today's busy lifestyles as well as improper eating habits, make it difficult for pregnant women to achieve adequate nutritional intake from diet alone. As a result, vitamin and nutrient supplementation may be an important adjunct to nutritional advice to pregnant women in order to maximize the health and neurologic outcomes of each infant born today. With so many potential dietary risks during pregnancy, many women find it difficult to select safe and nutritious diet. Healthcare providers can play an important role in providing expectant mothers with needed education and reassurance. In the end, how much risk a pregnant patient is willing to accept is her decision. Yet, with each concern, there are clear ways to lower the patient's risk and still enjoy eating.