The Active Female: Health Issues Throughout the Lifespan 2008th Edition

31. Nutritional Guidelines and Energy Needs During Pregnancy and Lactation

Jacalyn J. Robert-McComb Ángela García González  and Lesley Carraway1

(1)

Department of Health, Exercise, and Sports Sciences, Texas Tech University, Lubbock, TX, USA

(2)

Pharmaceutical and Health Sciences, University San Pablo-CEU, Urb. Montepríncipe; Ctra. Boadilla del Monte km 5.3, Alcorcón, Madrid, 28668, Spain

Jacalyn J. Robert-McComb (Corresponding author)

Email: jacalyn.mccomb@ttu.edu

Ángela García González

Email: angargon@fusp.ceu.es

Abstract

From a nutritional point of view, pregnancy and lactation are the most demanding physiological situations in a woman’s life. Requirements for all nutrients increase and optimal energy, and nutrient intake during pregnancy and lactation are basic for the actual and future health of both mother and child. Because successful pregnancy depends upon previous nutritional status of the mother, all women of childbearing age should be encouraged to consume a variety of nutrient-dense foods and beverages within and among the basic food groups while choosing foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt, and alcohol. Special attention must be paid to intake of micronutrients such as folic acid, vitamin D, iron, and iodine. A deficit in folic acid intake during the first 8 weeks of conception may lead to malformations (neural tube defects) which can be prevented by daily intake of 600 μg of folates from diet, supplements, or nutrient-enriched foods. Vitamin D deficiency among pregnant women can result from inadequate cutaneous synthesis, limited dietary intake of vitamin D, or vitamin D pathway impairment, and can lead to osteoporosis in the mother and/or rickets, hypocalcemia, delayed ossification, and abnormal enamel formation in the children as well as immune dysfunction. The DRI for vitamin D, during pregnancy and lactation, is 600 IU (15 μg)/day. There are not many natural foods rich in vitamin D so, apart from cold water fish, fortified foods are the main sources of this vitamin. Iron and iodine are also problematical nutrients which deficiencies are prevalent during gestation and lactation and so the need for their supplementation must be carefully evaluated. About energy, during pregnancy, women should consume an additional 300 kcal per fetus; however, women who are active during their pregnancy may need extra calories for exercise, and ideally, this additional energy should come from added servings of carbohydrate because carbohydrate intake meets the growth needs of the fetus and provides energy for exercise.

Keywords

Nutritional requirements during pregnancyFolic acidVitamin DIron and iodine intakes during pregnancyEnergy requirements during pregnancy

31.1 Learning Objectives

After completing this chapter, you should have an understanding of the following:

·               Nutritional guidelines during pregnancy and lactation

·               Energy requirements during pregnancy and lactation

·               Important nutrients, vitamins, and minerals for optimal pregnancy and infancy outcomes

·               The importance of iron reserves prior to conception

·               Folic acid supplementation

·               Vitamin D deficiency in women with dark complexions and limited sun exposure

31.2 Introduction

Optimal nutrient intake during pregnancy and lactation is basic for the actual and future health of both mother and child. The optimum recommended levels of folic acid, iron, essential fatty acids, and other vitamins for pregnant women has been a topic of discussion in the research literature. Controversial topics for optimal nutrition during pregnancy will be reviewed in this chapter as well as the general consensus for overall recommendations [14].

General dietary guidelines for pregnant women are similar to guidelines recommended for nonpregnant women for optimum health. However, the recommended levels of essential nutrients, vitamins, and minerals that pregnant women should consume are higher than that for the nonpregnant woman.

The overall quality of a woman’s diet affects her need for supplementation. If all of the necessary nutrients can be consumed in the daily diet, then supplements are not needed [5]. Yet, studies consistently show that many women, even in industrialized countries, may have vitamin and mineral deficiencies that could have an adverse effect on infant development [246].

31.3 Research Findings

31.3.1 Nutritional Guidelines During Pregnancy and Lactation

Dietary reference intakes (DRI) for pregnant and lactating women can be found at http://​fnic.​nal.​usda.​gov/​dietary-guidance/​dietary-reference-intakes/​dri-tables. There are essential nutrients, minerals, and vitamins that pregnant and lactating women must obtain through either a well-balanced nutrient-dense diet or a diet supplemented with vitamins, minerals, and essential nutrients and fortified foods.

General dietary guidelines for healthy pregnant women include the following recommendations: protein should comprise 20 % of a normal pregnancy diet. Fat should comprise approximately 30 % of diet in pregnancy and carbohydrates the remaining 50 %. A sample diet in pregnancy based on the Position of the American Dietetic Association should include nine servings of cereals, three servings of fruits, four servings of vegetables, two to three servings of dairy products, and four servings of meats, beans, or nuts [7].

Total caloric intake will vary according to body mass index (BMI), age, and semester, but the average recommendation is 2,500 kcal/day [8]. It is suggested that the additional calories needed for pregnancy (300 kcal and 10 g of protein per fetus) come from adding one protein and one dairy serving [9].

31.3.2 Important Nutrients, Vitamins, and Minerals for Optimal Pregnancy/Infant Outcomes

31.3.2.1 Iron

Adequate prepregnancy iron reserves can be achieved by an (a) adequate diet, (b) food fortification, or (c) preventive iron supplementation (low daily doses or weekly doses). Ideally, the last two types of intervention should include folate and, if needed, other nutrients such as vitamin A and zinc [2].

However, the best way to obtain nutrients is through diet. The amount of iron absorption depends upon the amount of iron in the diet, its bioavailability, and physiological requirements. Approximately 15 % of dietary iron is absorbed. The main sources of dietary heme iron are hemoglobin and myoglobin from red meats, fish, and poultry. Heme iron is absorbed two- to threefold more readily than nonheme iron. Meat also contains organic compounds that promote the absorption of iron from other less bioavailable nonheme iron sources. Approximately 95 % of the dietary iron intake is from nonheme iron sources. Vitamins significantly enhance iron absorption from nonheme foods, the size of this effect increases with the quantity of vitamin C in the meal [10].

Physiological iron requirements are three times higher in pregnancy than they are in the menstruating woman. A pregnant woman must consume an additional 700–800 mg of iron throughout her pregnancy: 3,100 mg for hematopoiesis and 3,000 mg for fetal and placental tissues [11].

Ideally, to meet iron needs during gestation, women should have 300 mg or more of iron reserves prior to conception [12]. Studies have shown that the best outcome conditions (birth weight, delivery time, and maternal health) have been reported to occur when hemoglobin level at term is between 931 and 1,231 g/L [1314]. Correction of anemia during pregnancy is difficult and should be prevented if possible.

Maternal anemia is defined by a hematocrit of less than 32 % and a hemoglobin level of less than 11 g/dL [11]. Among pregnant women, the prevalence of anemia in Africa exceeds 310 %, while it exceeds 40 % in Asia and exceeds 30 % in Latin America and Oceania. Anemia is generally less frequent among pregnant women in Europe (18.7 %) and in the USA (6 %). The exception in the USA being low-income and minority populations, in this group prevalence can reach 7–8 % or even 33 % in the third trimester of gestation [1517].

31.3.2.2 Folic Acid

It is well established that periconceptional supplementation with folic acid can reduce the incidence of neural tube defects (NTD) by 50 %. Data are available to advise all women who are capable of becoming pregnant to have periconception (i.e., at least 1 month before and until 3 months after conception) folic acid or multivitamin (including 0.4–0.8 mg of folic acid) supplementation to reduce the occurrence of NTDs and other major congenital abnormalities [18]. Additionally, the use of multivitamins containing folic acid and other B vitamin [1921] showed a higher efficacy (90 %) in the reduction of NTDs than using a high dose of folic acid alone (70 %) [22] or a low dose of folic acid (41–79 %) [23].

Periconceptional is defined as 3 months prior to conception. This finding is the basis for the Center for Disease Control and Prevention’s (CDC) recommendation that women of childbearing age who have a chance of becoming pregnant consume 0.4 mg of folate per day from 1 month preconception until the end of the first trimester. Folic acid supplementation should continue 3 months in the postconception period also.

Breastfeeding women have higher folate requirements due to the folate supplied through breast milk. The folate concentration in human milk is tightly regulated and not affected by maternal folate status, except in clinically folate-deficient mothers. A higher folate intake will maintain a normal folate status of the mother. An infant consumes about 0.8 L/day of breast milk with an average concentration of 831 mcg/L, so mother losses through the milk about 66 mcg/L folate which implies an additional requirement of 133 mcg/day of folates [24].

Interestingly, epidemiological evidence suggests that the development of NTDs is not primarily because of the lack of sufficient folate in the diet but arises from genetically determined changes in the uptake, in metabolism, or in maternal and, particularly fetal cells [25]. Therefore, the gene–environmental interaction between vitamin dependency and nutrition may have a causal role in NTDs [18]. A sensitive and vulnerable period for fetuses is from the third to the eighth week after conception. Supplementation with folic acid-containing multivitamins or folic acid alone may cause an increase in folate metabolite concentrations of tissue fluids and it may overcome the failure of the local metabolite supply.

31.3.2.3 Vitamin D

The National Research Council’s recommended dietary allowance for vitamin D, during pregnancy and lactation, is 10 mcg/day [8]. There are not many natural foods rich in vitamin D, so apart from cold water fish (salmon, mackerel, sardines, etc.), fortified foods are the main sources of this vitamin. More clinical trials are needed to identify effective preventive strategies during pregnancy to achieve vitamin D adequacy [626].

Vitamin D deficiency among pregnant women is not restricted to poor countries but also occurs in highly industrialized countries, more specifically to the disadvantaged subpopulations with limited sun exposure [627]. Vitamin D deficiencies can result from inadequate cutaneous synthesis, limited dietary intake of vitamin D, or vitamin D pathway impairment [28].

Obesity is also a risk factor to develop vitamin D deficiency. Vitamin D is absorbed with fat as part of chylomicrons and is taken up first by peripheral tissues that express lipoprotein lipase, especially adipose tissue and skeletal muscle. This pathway predicts that increased adiposity should lead to lower serum 231OHD levels [29].

Throughout gestation, if a woman is vitamin D deficient, it appears to impact fetal bone health more than maternal [3032]. Such deficiency in pregnant women can lead to rickets, hypocalcemia, delayed ossification, and abnormal enamel formation in children and osteoporosis, osteomalacia, and bone fractures in adults [6273334].

But Vitamin D is not only the “bones vitamin,” but it has also an important role in immune function. This function is developed in two ways: upregulation of the innate immune system and downregulation of the adaptive immune system [3537]. The innate immune system, also known as nonspecific immune system, provides immediate defense against infection. The cells of the innate system recognize and respond to pathogens in a generic way, but it does not confer long-lasting or protective immunity to the host. The adaptive immune system, also known as the specific immune system, is composed of highly specialized, systemic cells and processes that eliminate or prevent pathogenic growth. It is an adaptive immunity because the body’s immune system prepares itself for future challenges. Some studies suggest that the impact of vitamin D deficiency on immunity is stronger than the one on calcium metabolism and bone health as the risk of rickets increases significantly when total circulating 231(OH)D falls below 10 ng/mL (231 nmol/L), whereas cathelicidin mRNA expression, a marker of immune function, continues to be suppressed until 231(OH)D-circulating levels reach at least 20 ng/mL (310 nmol/L) [38] suggesting limit should be higher.

The lower limit of normal for 231(OH)D is controversial with suggested values in the literature ranging from 131 to 140 nmol/L [6263438]. In 2010, the Institute of Medicine raised the minimum 231(OH)D concentration from 10 ng/mL (231 nmol/L) to 20 ng/mL (310 nmol/L) [1629].

Vitamin D sufficiency can be attained by enough exposure to sunlight and/or diet. The amount of sunlight sufficient to achieve optimal vitamin D status varies depending on a host of factors such as the time of day, the time of year, the latitude, degree of skin pigmentation, type and extend of clothing, and body surface area exposed. The recommendation to have good vitamin D synthesis through the skin is 10 min exposure to sun light, face and bare arms, without sunscreen, three times a week.

Circulating serum 231OHD levels are currently the best available indicator of the net-incoming contributions from cutaneous synthesis and total intake (foods and supplements). Thus, the serum 231OHD level may function as a biomarker of exposure.

31.3.2.4 Iodine

Nearly two thirds of the 600 million people in Western and Central Europe live in regions of mild to severe iodine deficiency [39]. The National Research Council’s RDA for iodine during pregnancy is 160 mcg/day and 209 mcg/day for women during lactation (see http://​fnic.​nal.​usda.​gov/​dietary-guidance/​dietary-reference-intakes/​dri-tables) [8]. The removal of iodate conditioners in store-bought breads, the recommendations to reduce salt and egg intake, the use of noniodized salt in manufactured foods, and the reduction of meals made at home have reduced the US population iodine intake. Even though the National Health and Nutrition Examination Survey (NHANES) shows that iodine intake is adequate in general population, certain groups such as pregnant women were found to have a median urinary iodine concentration of 1,231 mcg/L (which will correlate with an intake of 178 mcg of iodine and 58 % of this group showed iodine intakes under the National Health and Nutrition Examination Survey’s recommendations (220 mcg/day) [40].

In 2007, the World Health Organization/The United Nations Children’s Fund/The International Council for the Control of Iodine Deficiency Disorders (WHO/UNICEF/ICCIDD) increased the recommended nutrient intake for iodine, during pregnancy, from 200 to 250 mcg, but stated clearly that more data are needed to establish the level of iodine intake that ensures maternal and newborn euthyroidism. Euthyroidism is the physiological state characterized by normal serum levels of thyroid hormone [41].

Pregnancy causes an increase in thyroid hormone requirements that can only be met by a proportional increase in hormone production that directly depends upon the availability of dietary iodine. This fact, together with an increase in urine losses because of the higher glomerular filtration during pregnancy, explains why gestation is a goitrogenic situation. Goitrogens are substances that suppress the function of the thyroid gland by interfering with iodine uptake, which can, as a result, cause an enlargement of the thyroid, i.e., a goiter. When iodine intake is restricted, even moderately, physiological adaptations lead to excessive glandular stimulation, hypothyroxinemia, and goiter formation. These conditions may only partially regress after parturition or childbirth.

Iodine deficiency during pregnancy and lactation has important repercussions for both mother and fetus. Thyroid hormones are fundamental in neuron migration to brain cortex and for the central nervous system development [4245]. The fetal brain is particularly vulnerable to maternal hypothyroidism, and even subclinical hypothyroidism during pregnancy can impair mental development of the newborn as it increases infant mortality and growth retardation [4245].

For nearly all countries the primary strategy for sustainable elimination of iodine deficiency is universal salt iodization. However, many countries have started to give indiscriminate iodine supplementation with a daily dose of 150 mcg of iodine. Prudency about supplementation with iodine is recommended. Some recent studies are suggesting long-term undesirable consequences for the newborn after iodine supplementation during pregnancy [46].

31.3.3 Energy Requirements During Pregnancy and Lactation

The energy requirements of pregnancy are those needed for adequate maternal gain to ensure the growth of the fetus, placenta, and associated maternal tissues, and to provide for the increased metabolic demands of pregnancy, in addition to the energy needed to maintain adequate maternal weight, body composition, and physical activity throughout the gestational period, as well as for sufficient energy stores to assist in proper lactation after delivery. Recommendations for energy intake of pregnant women should be population specific, because of differences in body size, lifestyle, and underlying nutritional status; special considerations must be taken into account for women who are underweight or overweight when entering into the pregnancy period.

Estimated energy recommendations (EER) from the National Research Council for pregnant and lactating women can be found in the dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients) [8]. The EER is defined as the average dietary energy intake that is predicted to maintain energy balance in a healthy adult of a defined age, gender, weight, height, and level of physical activity, consistent with good health. This information can also be downloaded free of charge at http://​www.​nap.​edu/​openbook.​php?​isbn=​0309085373. Appendices 1and 2 contain these referenced equations for pregnant and lactating women.

The EER from the National Research Council [8] is based on the components of total energy expenditure (TEE) which include (a) the basal metabolic rate (BMR) or basal metabolism (including thermoregulation) over 24 h (the BEE); for convenience, resting metabolic rate (RMR) is sometimes used or energy expenditure under resting conditions (note: it is not the same as BMR) extrapolated to 24 h (REE); (b) the thermic effect of food (TEF) or diet-induced thermogenesis (DIT); and (c) energy expended for physical activity which is commonly described as the ratio of total to basal daily energy expenditure (TEE/BEE). This ratio is known as the physical activity level (PAL) or the physical activity index.

Basal metabolic rate describes the rate of energy expenditure that occurs in the postabsorptive state. This state is defined as the particular condition that prevails after an overnight fast, the subject having not consumed food for 12–14 h. The participant should be resting comfortably, supine, awake, and motionless in a thermo-neutral environment. Basal metabolic rate is commonly extrapolated to 24 h to be more meaningful, and it is then referred to as BEE (basal energy expenditure), expressed as kcal/24 h. This value is affected by body size as well as lean body mass.

Thermoregulation is held within a narrow zone for humans. Increases in energy occur when ambient temperatures are below the zone of thermo neutrality. The thermo-neutral zone is the environmental temperature at which oxygen consumption and metabolic rate are lowest.

Resting metabolic rate (RMR) or energy expenditure under resting conditions tends to be somewhat higher (10–20 %) than under basal metabolic conditions (BMR). This is due to increases in energy expenditure caused by recent food intake or by the delayed effect of recently completed physical activity. It is important to distinguish between BMR and RMR and between BEE and REE (resting energy expenditure extrapolated to 24 h).

The thermic effect of food was originally referred to as the specific dynamic action (SDA) of food. It is more commonly referred to as the thermic effect of food (TEF) in more recent literature or diet-induced thermogenesis (DIT).

The energy expended for physical activity varies greatly among individuals as well as from day to day. The level of physical activity is commonly described as the ratio of total to basal daily energy expenditure (TEE/BEE). Describing physical activity habits in terms of PAL (physical activity level or TEE/BEE) is a convenient comparison and is used in the EER from the National Research Council to describe and account for physical activity habits. The estimated energy for physical activity (EEPA) is the most variable component of TEE.

Physical activity level or PAL in a nonpregnant state must be computed for the equations using age, weight, height, and gender. The PAL values obtained in pregnant women, especially during the second part of pregnancy, are lower than values obtained in nonpregnant individuals. Pregnancy is often associated with a comparatively large increase in BMR, whereas the effect of pregnancy on energy expenditure when performing many specific activities tends to be rather small [47].

Doubly labeled water studies have also been conducted using well-nourished pregnant and lactating women [4853]. Results of the energy needs during pregnancy and lactation can be found in Tables 31.1and 31.2, respectively. Because energy requirements in pregnancy are increased by approximately 17 % over the nonpregnant state, a woman of normal weight should consume an additional 300 kcal/day, and those calories should be concentrated in foods of high-nutrient density, a value based on the percent protein, vitamins, and minerals per 100 kcal [554].

Table 31.1

Doubly labeled water pregnancy studies

References

n

Gestation week

Pregravid weight (kg)

Gestational weight gain (kg)

Total energy expenditure (kcal/day)

Physical activity level

Activity energy expenditure (kcal/day)

[48]

10

10

2,470

1.42

731

[49]

22

0

60.8

13.5

2,484

1.87

1,147

22

16–18

   

2,293

1.65

860

22

30

   

2,986

1.82

1,338

19

36

   

2,914

1.66

1,171

[50]

12

0

61.7

11.91

2,274

1.58

835

6

   

2,322

1.54

818

12

   

2,426

1.64

939

18

   

2,456

1.65

964

24

   

2,621

1.66

1,042

30

   

2,675

1.62

1,026

36

   

2,688

1.50

885

[51]

10

0

11.6

2,205

1.68

892

8–10

   

2,047

1.57

743

24–26

   

2,410

1.56

867

34–36

   

2,728

1.61

1,038

Source: Adapted from the Institute of Medicine (US), Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary reference intakes for energy carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. Washington, DC: National Academy Press, 2002

Table 31.2

Doubly labeled water lactation studies

References

n

Activity

Stage of lactation (months)

Total energy expenditure (kcal/day)

Total energy expenditure (kcal/kg/day)

Physical activity level

Energy expenditure (kcal/day)

Milk energy output (kcal/day)

Energy mobilization (kcal/day)

Energy requirement (kcal/day)

[48]

10

1

2,109

35.8

1.50

703

536

Gained fat

2,646

2

2,171

36.9

1.55

774

532

Mass

2,702

3

2,138

36.5

1.59

793

530

 

2,667

[49]

23

2

2,532

39.3

1.82

1,123

502

72

2,962

6

2,580

41.0

1.79

1,123

     

[53]

 9

3–6

2,413

37.2

1.75

1,037

538

287

2,663

[51]

10

1

2,146

1.62

[52]

24

3

2,391

38.1

1.79

1,061

483

155

2,719

Source: Adapted from the Institute of Medicine (US), Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary reference intakes for energy carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. Washington, DC: National Academy Press, 2002

Multifetal pregnancies in the USA increased by 77 % from 1980 to 2003 largely because of assisted reproduction treatments [55]. Although the exact caloric requirements for multiple gestations have not been well described, it is generally recommended that an additional 300 kcal and 10 g of protein per fetus beyond singleton are standard [556].

31.3.4 Additional Energy Requirements for the Exercising Woman During Pregnancy and Lactation

Women who are active during their pregnancy need extra calories for exercise. Recent studies have found that between 41 and 61 % of women engage in regular leisure physical activity during pregnancy [57]. At the same time, the percentage of women within the work force has increased, and more women engage in physically demanding lines of work (such as police officers, fire fighters, military personnel). Furthermore, there has been an increase in the interest of adult women to join fitness clubs and participate in exercise programs as part of a healthy lifestyle corresponding with a rise in the incidence of overweight and obese women worldwide.

This additional energy should come from added servings of carbohydrate because carbohydrate intake meets the growth needs of the fetus and provides energy for exercise [58]. Carbohydrates are the main fuel both for fetus and muscles so, while doing exercise, there can be a competition for blood glucose that can lead to hypoglycemia periods which can be dangerous both for the mother and the offspring.

The RDA recommended by the IOM of 1,731 g/day of CH [18] may not be sufficient to cover the necessities of being an active pregnant woman. The ingestion of a carbohydrate-rich snack before any practice of sportive activity is advised [57]. The combination of energy demands for childbearing necessities, and the additional energy needed for an active lifestyle may require personal and customized dietary advice for active pregnant women. Micronutrient status is another potential problem for an active pregnancy. For example, athletes usually have lower iron tissue stores before pregnancy and so are more likely to have iron deficiencies. Vitamin D and calcium status can also be a problem [575960].

31.3.5 Weight Gain During Pregnancy

Weight gain during pregnancy comprises the products of conception (fetus, placenta, amniotic fluid), the growth of various maternal tissues (uterus, breasts), and the increase in blood, extracellular fluid, and maternal fat stores. An inadequate weight gain is associated with intrauterine growth retardation, preterm birth, preeclampsia, eclampsia, and postpartum hemorrhage and later obesity of the offspring and mother [6163].

The optimal amount of prenatal weight gain is modified by a woman’s prepregnancy weight for height (body mass index [BMI]). Total weight gain varies widely among women. Well-nourished women should gain 10–14 kg during pregnancy, with an average of 12 kg, in order to increase the probability of delivering full-term infants with an average birth weight of 3.3 kg and to reduce the risk of fetal and maternal complications. The mean rate of weight gain is 1.6 kg in the first trimester and 0.44 kg/week in the second and third trimesters. For underweight women, the mean rate of weight gain is 2.3 kg in the first trimester and 0.49 kg/week in the second and third trimesters. For overweight women, the mean rate of weight gain is 0.9 kg in the first trimester and 0.30 kg/week in the second and third trimesters [64].

Following the National Academy of Sciences, Institute of Medicine (IOM), recommendations [64] total weight gain ranges are 11–15 kg (25–35 lb) for normal-weight women (19.5 < BMI > 25.9), 12.7–18 kg (28–40 lb) for underweight women (BMI < 19.8), and 7–11 kg (15–25 lb) for an overweight woman (BMI > 26). This translates to 0.4 kg/week for normal-weight women, 0.31 kg/week for underweight women, and 0.3 kg/week for overweight women. Women with a BMI > 29.0 (obesity) should be advised to gain at a rate that does not exceed 11.4 kg (25 lb) throughout total pregnancy and have a minimum gain of 7 kg (15 lb) [7]. The impact of maternal weight gain in the second trimester is most important for fetal development and is protective of fetal growth even if the overall weight gain is poor [5].

In the USA excessive weight gain during gestation remains of predominant concern, as 60 % of obese women gain more than recommended and, also, approximately 40 % of normal-weight women gain more than recommended [65]. Pregnancy-related obesity can lead to a lifetime of unhealthy weight for the mother and her offspring and to health problems as gestational diabetes or hypertension. Therefore, many women want or need to remain active during pregnancy, but little is known about the impact of exercise during pregnancy on nutritional requirements, nutrient intakes, and maternal weight gain, and whether these impact birth outcomes in physically active, pregnant women [6667].

31.4 Contemporary Understanding of the Issues

The overall quality of a woman’s diet affects her needs for supplementation. However, it has been found that iron supplementation during pregnancy increases maternal iron status and stores and improves pregnancy outcome, when the mother is anemic or from a population in which anemia prevalence is high [6869]. That is the main reason why the IOM recommends a daily supplement containing 16–20 mg of iron during pregnancy for healthy women with a mixed diet [70]. The supplement should also include vitamin B12 and 400 mcg (0.4 mg) of folic acid per daily dose [71].

According to the Department of Health and Human Services and the Department of Agriculture [72], a healthy eating pattern focuses on nutrient-dense foods—vegetables, fruits, whole grains, fat-free or low-fat milk and milk products, lean meats and poultry, seafood, eggs, beans and peas, and nuts and seeds that are prepared without added solid fats, sugars, starches, and sodium. Combined into an eating pattern, these foods can provide the full range of essential nutrients and fiber, without excessive calories. The oils contained in seafood, nuts and seeds, and vegetable oils added to foods also contribute essential nutrients.

The nutritional value of seafood is of particular importance during fetal growth and development, as well as in early infancy and childhood. Moderate evidence indicates that intake of omega-3 fatty acids, in particular DHA, from at least 8 oz of seafood per week for women who are pregnant or breastfeeding is associated with improved infant health outcomes, such as visual and cognitive development. Due to their methyl mercury content, limit white (albacore) tuna to 6 oz per week and do not eat the following four types of fish: tilefish, shark, swordfish, and king mackerel.

The Dietary Guidelines for Americans 2010 (http://​www.​cnpp.​usda.​gov/​DGAs2010-PolicyDocument.​htm) include the following key recommendations for all population groups [73]:

·               Follow a healthy eating pattern while staying within calorie needs.

·               Increase vegetable and fruit intake.

·               Eat a variety of vegetables, especially dark-green and red and orange vegetables and beans and peas.

·               Consume at least half of all grains as whole grains. Increase whole-grain intake by replacing refined grains with whole grains.

·               Increase intake of fat-free or low-fat milk and milk products, such as milk, yogurt, cheese, or fortified soy beverages.

·               Choose a variety of protein foods, which include seafood, lean meat and poultry, eggs, beans and peas, soy products, and unsalted nuts and seeds.

·               Increase the amount and variety of seafood consumed by choosing seafood in place of some meat and poultry.

·               Replace protein foods that are higher in solid fats with choices that are lower in solid fats and calories and/or are sources of oils.

·               Use oils to replace solid fats where possible.

·               Choose foods that provide more potassium, dietary fiber, calcium, and vitamin D, which are nutrients of concern in American diets. These foods include vegetables, fruits, whole grains, and milk and milk products.

·               Women capable of becoming pregnant should choose foods that supply heme iron, which is more readily absorbed by the body. They should consume additional iron sources as well as enhancers of iron absorption such as vitamin C-rich foods.

·               Women capable of becoming pregnant should consume 400 micrograms (mcg) per day of synthetic folic acid (from fortified foods and/or supplements) in addition to food forms of folate from a varied diet. The major dietary sources of folates are fresh and frozen green leafy vegetables, citrus fruits and juices, liver, wheat bread, and legumes.

·               Women who are pregnant or breastfeeding should consume 8–12 oz of seafood per week from a variety of seafood types.

·               If pregnant, take an iron supplement as recommended by an obstetrician or other health-care provider [7475].

31.5 Future Directions

It is thought that prepregnancy iron reserves can be achieved by an adequate diet, food fortification, or preventive iron supplementation (low daily doses or weekly doses). Ideally, the last two types of intervention should include folate and, if needed, other nutrients such as vitamin A and zinc [2].

Not all countries and all people have the necessary financial resources to provide nutrient-dense foods, healthy environments, and healthy lifestyles that contribute to or provide the essential vitamins and minerals needed for a robust pregnancy. For example, results from a review of vitamin D deficiency in pregnant women indicated that 331 of the 76 studies reviewed reported that the mean or median maternal concentrations of 231(OH)D levels were 331 nmol/L or less that represents the lower limits of normal. Low concentrations were reported among different ethnic groups in many regions including North America, Europe, the UK, Africa, the Middle East, and Asia. In the USA the degree of deficiency is greatest in those with darker pigmentation, i.e., African-American women, but deficiency exists among Hispanic and Caucasian women who have limited access to sunlight, either through limited activity outdoors, type of clothing, cultural practices, or thorough use of sunscreen when outdoors [7475].

From a global public health perspective, food fortification with folic acid and some other B vitamins (B12 and B6) may be the most effective method to prevent NTDs in unplanned pregnancies [18]. In Hungary [76], three vitamins (folic acid [160 mcg], vitamins B12 [0.8 mcg], and vitamin B6 [0.864 mcg]) were added to 100 g of flour [77].

The concept of weekly iron–folic acid supplementation as a public health approach to prevent iron anemia was presented at the 1993 World Health Organization/United Nations University meeting [78]. It appears that small daily doses as recommended by the Food and Drug Administration [79] and the Food and Nutrition Board and IOM [81] as well as weekly dosing starting early in pregnancy are safer and essentially as efficacious as daily iron in preventing iron deficiency and improving iron nutrition when adherence is satisfactory [2] for females with iron deficiency anemia; therapy consists of 60–120 mg of ferrous iron in divided doses throughout the day [79]. The therapeutic dose depends on the hemoglobin level of the pregnant woman. For more complete guidelines, please refer to the guidelines for the assessment of iron deficiency in women of childbearing age and the IOM recommended guidelines for the prevention, detection, and management among US children and women of childbearing age for iron deficiency anemia [7980]. Even for nonpregnant women, long-term weekly supplementation with iron and folic acid can bring benefits in terms of the prevention of neural tube defects and hyperhomocysteinemia early in pregnancy [81].

However, there is not a universal consensus regarding the type of supplementation and the dose of folic acid. Even though the mandatory fortification of standardized enriched cereal grain products in the USA in 1998 resulted in a substantial increase in blood folate concentrations and a concomitant decrease in 36 % of NTD prevalence, mandatory fortifications have raised concerns about the consequences of excessive intakes.

Excessively high intakes of folic acid may cause harmful effects, including progression of nerve damage in B12-deficient persons, excess intake in children, accumulation of unmetabolized folic acid, blunting of antifolate therapy (methotrexate and phenytoin), accelerated cognitive decline in the elderly, epigenetic hypermethylation, and cancer promotion [82]. These findings are mainly attributed to an excess of folate intake and to the presence of no metabolized folic acid in plasma of people receiving very high doses of folic acid [24]. More data are needed to find the right equilibrium between fortification and supplementation while accomplishing the needs of the most nutrition vulnerable populations.

31.6 Concluding Remarks

The overall quality of a woman’s diet affects her needs for supplementation and nutritional counseling advice. Excess or deficiency of any nutrient, vitamin, or mineral is a concern during pregnancy. Optimal pregnancy outcomes occur when women maintain a balanced diet prior to conception. Therefore, all women of childbearing age should be encouraged to consume a variety of nutrient-dense foods and beverages within and among the basic food groups while choosing foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt, and alcohol. Specifically, women of childbearing age who may become pregnant should eat foods high in heme iron and/or consume iron-rich plant foods or iron-fortified foods with an enhancer of iron absorption, such as vitamin C-rich foods. Women of childbearing age who may become pregnant and those in the first trimester of pregnancy should consume adequate synthetic folic acid daily (from fortified foods or supplements) in addition to food forms of folate from a varied diet.

During pregnancy, women should consume an additional 300 kcal and 10 g of protein per fetus. It is suggested that the additional calories needed for pregnancy come from adding one protein and one dairy serving [9]. Women who are active during their pregnancy may need extra calories for exercise above the additional protein and dairy servings. Ideally, this additional energy should come from added servings of carbohydrate because carbohydrate intake meets the growth needs of the fetus and provides energy for exercise [58].

Lastly, it is recommended that women who are most vulnerable to congenital malformations be counseled preconceptionally. There is a fourfold increased risk of congenital malformations related to poor control of diabetes during embryogenesis. Also, girls under the age of 17 are at increased risk for preterm delivery, perinatal mortality, and low body weight. Specifically, girls within 2 years of menarche may require additional energy, protein, and calcium, to meet their nutritional needs for maternal and fetal growth. The erratic use of vitamin supplementation, poor nutrition, and body image issues for this specific population suggests that additional counseling may be warranted [5].

Women of childbearing age who may become pregnant and those in the first trimester of pregnancy should consume adequate synthetic folic acid daily (from fortified foods or supplements) in addition to food forms of folate from a varied diet.

Appendix 1 Physical Activity Level Categories and Walking Equivalence

 

Walking equivalence (mi/day at 3–4 mph)

PAL category

PAL range

PAL

Lightweight individual (44 kg)

Middleweight individual (70 kg)

Heavyweight individual (120 kg)

Sedentary

1.0–1.39

1.25

~0

~0

~ 0

Low active

1.4–1.59

       

 Mean

 

1.5

 2.9

 2.2

 1.5

Active

1.6–1.89

       

 Minimum

 

1.6

 5.8

 4.4

 3.0

 Mean

 

1.75

 9.9

 7.3

 5.3

Very active

1.9–2.49

       

 Minimum

 

1.9

14.0

10.3

17.5

 Mean

 

2.2

22.5

16.7

12.3

 Maximum

 

2.5

31.0

23.0

17.0

Adapted from the National Research Council. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients). Washington, DC: The National Academies Press, 2005

In addition to energy spent for the generally unscheduled activities that are part of a normal daily life, the low, middle, and high miles/day values apply to relatively heavyweight (120 kg), midweight (70 kg), and lightweight (44 kg) individuals, respectively

Appendix 2 Estimated Energy Expenditure* Prediction Equations at Four Physical Activity Levels

EER for infants and young children 0–3 years

TEE (kcal/day) = 89 (±3 [standard error]) × weight of the child (kg) − 100 (±56 [standard error])

EER = TEE + energy deposition

0–3 months (89 × weight of infant [kg] − 100) + 175 (kcal for energy deposition)

4–6 months (89 × weight of infant [kg] − 100) + 56 (kcal for energy deposition)

7–12 months (89 × weight of infant [kg] − 100) + 22 (kcal for energy deposition)

13–36 months (89 × weight of child [kg] − 100) + 20 (kcal for energy deposition)

Where PA = physical activity coefficient:

PA = 1.0 if PAL is estimated to be ≥ 1.0 < 1.4 (sedentary)

PA = 1.13 if PAL is estimated to be ≥ 1.4 < 1.6 (low active)

PA = 1.26 if PAL is estimated to be ≥ 1.6 < 1.9 (active)

PA = 1.42 if PAL is estimated to be ≥ 1.9 < 2.5 (very active)

EER for girls 3–8 years

TEE = see doubly labeled water data used to predict energy expenditure for standard error in the dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients) at http://​www.​nap.​edu/​openbook.​php?​isbn=​0309085373

EER = TEE + energy deposition

EER = 135.3 − (30.8 × Age [years]) + PA × (10 × weight [kg] + 934 × height [m]) + 20 (kcal for energy deposition)

Where PA = physical activity coefficient:

PA = 1.0 if PAL is estimated to be ≥ 1.0 < 1.4 (sedentary)

PA = 1.16 if PAL is estimated to be ≥ 1.4 < 1.6 (low active)

PA = 1.31 if PAL is estimated to be ≥ 1.6 < 1.9 (active)

PA = 1.56 if PAL is estimated to be ≥ 1.9 < 2.5 (very active)

EER for girls 9–18 years

TEE = see doubly labeled water data used to predict energy expenditure for standard error in the dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients) at http://​www.​nap.​edu/​openbook.​php?​isbn=​0309085373

EER = TEE + energy depositions

EER = 135.3 − (30.8 × age [years]) + PA × (19 × weight [kg] + 934c height [m]) + 25 (kcal for energy deposition)

Where PA = physical activity coefficient:

PA = 1.0 if PAL is estimated to be ≥ 1.0 < 1.4 (sedentary)

PA = 1.16 if PAL is estimated to be ≥ 1.4 < 1.6 (low active)

PA = 1.31 if PAL is estimated to be ≥ 1.6 < 1.9 (active)

PA = 1.56 if PAL is estimated to be ≥ 1.9 < 2.5 (very active)

EER for women 19 years and older

EER = 354 − (6.91 × age [years]) + PA × (9.36 × weight [kg] + 726 × height [m])

Where PA = physical activity coefficient:

PA = 1.0 if PAL is estimated to be ≥ 1.0 < 1.4 (sedentary)

PA = 1.12 if PAL is estimated to be ≥ 1.4 < 1.6 (low active)

PA = 1.27 if PAL is estimated to be ≥ 1.6 < 1.9 (active)

PA = 1.45 if PAL is estimated to be ≥ 1.9 < 2.5 (very active)

EER for pregnant women (14–18 years)

EER pregnant = adolescent EER nonpregnant + additional energy expended during pregnancy + energy deposition

First trimester = adolescent EER + 0 + 0

Second trimester = adolescent EER + 160 kcal (8 kcal/week × 20 week) + 180 kcal

Third trimester = adolescent EER + 272 kcal (8 kcal/week × 24 week) + 180 kcal

EER for pregnant women (19–50 years)

EER pregnant = adult EER nonpregnant + additional energy expanded during pregnancy + energy deposition

First trimester = adult EER + 0 + 0

Second trimester = adult EER + 160 kcal (8 kcal/week × 20 week) + 180 kcal

Third trimester = adult EER +272 kcal (8 kcal/week × 34 week) + 180 kcal

EER for lactating women (14–18 years)

EER lactation = adolescent EER prepregnancy + milk energy output − weight loss

First 6 months = adolescent EER + 500 − 170

Second 6 months = adolescent EER + 400 − 0

EER for lactating women (19–50 years)

EER lactation = adult EER prepregnancy + milk energy output − weight loss

First 6 months = adult EER + 500 − 170

Second 6 months = adult EER + 400 − 0

Weight maintenance TEE in overweight girls 3–18 years or at risk of a high

TEE = 389 − (41.2 × age [years]) + PA × (15.0 × weight [kg] + 701.6 × height [m])

Where PA = physical activity coefficient:

PA = 1.0 if PAL is estimated to be ≥ 1.0 < 1.4 (sedentary)

PA = 1.12 if PAL is estimated to be ≥ 1.4 < 1.6 (low active)

PA = 1.24 if PAL is estimated to be ≥ 1.6 < 1.9 (active)

PA = 1.45 if PAL is estimated to be ≥ 1.9 < 2.5 (very active)

Overweight and obese women 19 years and older

TEE = 448 − (7.95 × age [years]) + PA × (11.4 × weight [kg] + 619 × height [m])

Where PA is the physical activity coefficient:

PA = 1.0 if PAL is estimated to be ≥ 1.0 < 1.4 (sedentary)

PA = 1.16 if PAL is estimated to be ≥ 1.4 < 1.6 (low active)

PA = 1.27 if PAL is estimated to be ≥ 1.6 < 1.9 (active)

PA = 1.44 if PAL is estimated to be ≥ 1.9 < 2.5 (very active)

Normal and overweight or obese women 19 years and older

TEE = 387 − (7.31 × age [years]) + PA × (10.9 × weight [kg] + 600.7 × height [m])

Where PA is the physical activity coefficient:

PA = 1.0 if PAL is estimated to be ≥ 1.0 < 1.4 (sedentary)

PA = 1.14 if PAL is estimated to be ≥ 1.4 < 1.6 (low active)

PA = 1.27 if PAL is estimated to be ≥ 1.6 < 1.9 (active)

PA = 1.45 if PAL is estimated to be ≥ 1.9 < 2.5 (very active)

Adapted from the National Research Council. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. Washington, DC: The National Academies Press, 200. See http://​www.​nap.​edu/​openbook.​php?​isbn=​0309085373

* Estimated energy expenditure (EER) is the average dietary energy intake that is predicted to maintain energy balance in a healthy adult of a defined age, gender, weight, height, and level of physical activity consistent with good health. In children and pregnant and lactating women, the EER includes the needs associated with the deposition of tissues or the secretion of milk at rates consistent with good health

Physical activity level (PAL) is the physical activity level that is the ratio of the total energy expenditure to the basal energy expenditure

Total energy expenditure (TEE) is the sum of the resting energy expenditure, energy expended in physical activity, and the thermic effect of food

Body mass index (BMI) is determined by dividing the weight (in kilograms) by the square of the height (in meters)

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