Maternal and Fetal Nutrition

Maternal and Fetal Nutrition

Shannon E. Perry

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M aternal nutritional status at the time of conception is a significant determinant of embryonic and fetal growth (Gardiner et al., 2008) and is one of the many factors that influence the outcome of pregnancy (Fig. 8-1). Nutrition is potentially alterable, and good nutrition before and during pregnancy is an important preventive measure for a variety of problems. These problems include birth of low-birth-weight (LBW; birth weight of 2500 g or less) and preterm infants (those born before 37 weeks of gestation). The 2% of infants born very preterm (less than 32 weeks of gestation) accounted for more than one half of all infant deaths in the United States in 2005. The infant mortality rate for late preterm infants (those born between 34 0/7 and 36 6/7weeks) was more than three times that for term infants (37 to 41 weeks) (Mathews & MacDorman, 2008). Evidence is growing that the mother’s nutrition and lifestyle affect the long-term health of her children (Gardiner et al.). Thus the importance of good nutrition must be emphasized to all women of childbearing potential. Key components of nutrition care during the preconception period and pregnancy include:

Nutrient Needs Before Conception image

The first trimester of pregnancy is a crucial one for embryonic and fetal organ development. A healthful diet before conception is the best way to ensure that adequate nutrients are available for the developing fetus. Folate or folic acid intake is of particular concern in the periconceptual period. Folate is the form in which this vitamin is found naturally in foods, and folic acid is the form used in fortification of grain products and other foods and in vitamin supplements. Neural tube defects, or failure in closure of the neural tube, are more common in infants of women with poor folic acid intake. Researchers estimate that the incidence of neural tube defects can be decreased by as much as 70% if all women had an adequate folic acid intake during the periconceptual period (Cornel, Smit, & de Jong-van den Berg, 2005). All women capable of becoming pregnant are advised to consume 400 mcg of folic acid daily in fortified foods (e.g., ready-to-eat cereals, enriched grain products) or supplements, in addition to a diet rich in folate-containing foods such as green leafy vegetables, whole grains, and fruits (see Box 8-5 later in this chapter).

Both maternal and fetal risks in pregnancy are increased when the mother is significantly underweight or overweight when pregnancy begins. Ideally, all women achieve a desirable body weight before conception.

Nutrient Needs During Pregnancy image

Nutrient needs are determined, at least in part, by the stage of gestation. The amount of fetal growth varies during the different stages of pregnancy. During the first trimester, the synthesis of fetal tissues places relatively few demands on maternal nutrition. Therefore during the first trimester, when the embryo or fetus is very small, the needs are only slightly increased over those before pregnancy. In contrast, the last trimester is a period of noticeable fetal growth when most of the fetal stores of energy sources and minerals are deposited. Basal metabolic rates (BMRs), when expressed as kilocalories (kcal) per minute, are approximately 20% higher in pregnant women than in nonpregnant women. This increase includes the energy cost for tissue synthesis.

The Food and Nutrition Board of the National Academy of Sciences publishes recommendations for the people of the United States, the Dietary Reference Intakes (DRIs) ( The DRIs consist of Recommended Dietary Allowances (RDAs) and Adequate Intakes (AIs), as well as Upper Limits (ULs), guidelines for avoiding excessive intakes of nutrients that may be toxic if consumed in excess. RDAs for some nutrients have been available for many years, and they have been revised periodically. RDAs are recommendations for daily nutritional intakes that meet the needs of almost all (97%-98%) of the healthy members of the population. AIs are similar to the RDAs and are believed to cover the needs of virtually all healthy individuals in a group, except that they deal with nutrients for which the data are insufficient to be certain of their requirements. The RDAs and AIs include a wide variety of nutrients and food components, and they are divided into age, sex, and life-stage categories (e.g., infancy, pregnancy, lactation). They can be used as goals in planning the diets of individuals (Table 8-1).


Recommendations for Daily Intakes of Selected Nutrients During Pregnancy and Lactation

Energy (kilocalories [kcal] or kilojoules [kJ]) Variable 1st trimester, same as nonpregnant; second trimester, nonpregnant needs + 81 kcal (340 kJ); 3rd trimester, nonpregnant needs + 108 kcal (452 kJ) 1st 6 months, nonpregnant needs + 79 kcal (330 kJ); 2nd 6 months, nonpregnant needs + 55 kcal (230 kJ) Growth of fetal and maternal tissues; milk production Carbohydrate, fat, and protein
Protein (g) 46 1st trimester, same as nonpregnant; 2nd and 3rd trimesters, nonpregnant needs + 25 g Nonpregnant needs + 25 g Synthesis of the products of conception; growth of maternal tissue and expansion of blood volume; secretion of milk protein during lactation Meats, eggs, cheese, yogurt, legumes (dry beans and peas, peanuts), nuts, grains
Water (L) 2.7 total (2.2 in beverages) 3 total (2.3 in beverages) 3.8 total (3.1 in beverages) Expansion of blood volume, excretion of wastes; milk secretion Water and beverages made with water, milk, juices; all foods, especially frozen desserts, fruits, lettuce and other fresh vegetables
Fiber (g) 25 28 29 Promote regular bowel elimination; reduce long-term risk of heart disease, diverticulosis, and diabetes Whole grains, bran, vegetables, fruits, nuts and seeds
Calcium (mg) 1300/1000 1300/1000 1300/1000 Fetal and infant skeleton and tooth formation; maintenance of maternal bone and tooth mineralization Milk, cheese, yogurt, sardines or other fish eaten with bones left in, deep green leafy vegetables except spinach or Swiss chard, calcium-set tofu, baked beans, tortillas
Iron (mg) 15/18 30 10/9 Maternal hemoglobin formation, fetal liver iron storage Liver, meats, whole grain or enriched breads and cereals, deep green leafy vegetables, legumes, dried fruits
Zinc (mg) 9/8 12/11 13/12 Component of numerous enzyme systems, possibly important in preventing congenital malformations Liver, shellfish, meats, whole grains, milk
Iodine (mcg) 150 220 290 Increased maternal metabolic rate Iodized salt, seafood, milk and milk products, commercial yeast breads, rolls, and donuts
Magnesium (mg) 360/310-320 400/350-360 360/310-320 Involved in energy and protein metabolism, tissue growth, muscle action Nuts, legumes, cocoa, meats, whole grains
A (mcg) 700 750/770 1200/1300 Essential for cell development, tooth bud formation, bone growth Deep green leafy vegetables; dark yellow vegetables; and fruits, chili peppers, liver, fortified margarine and butter
D (mcg) 5 5 5 Involved in absorption of calcium and phosphorus, improves mineralization Fortified milk and margarine, egg yolk, butter, liver, seafood
E (mg) 15 15 19 Antioxidant (protects cell membranes from damage), especially important for preventing breakdown of RBCs Vegetable oils, green leafy vegetables, whole grains, liver, nuts and seeds, cheese, fish
C (mg) 65/75 80/85 115/120 Tissue formation and integrity, formation of connective tissue, enhancement of iron absorption Citrus fruits, strawberries, melons, broccoli, tomatoes, peppers, raw deep green leafy vegetables
Folate (mcg) 400 600 500 Prevention of neural tube defects, support for increased maternal RBC formation Fortified ready-to-eat cereals and other grain products, green leafy vegetables, oranges, broccoli, asparagus, artichokes, liver
B6 or pyridoxine (mg) 1.2/1.3 1.9 2 Involved in protein metabolism Meats, liver, deep green vegetables, whole grains
B12 (mcg) 2.4 2.6 2.8 Production of nucleic acids and proteins, especially important in formation of RBC and neural functioning Milk and milk products, eggs, meats, liver, fortified soy milk



RBCs, Red blood cells.

*When two values appear, separated by a diagonal slash, the first is for females younger than 19 years, and the second is for those 19 to 50 years of age.

The international metric unit of energy measurement is the joule (J). 1 kcal = 4.184 kJ.

Add an additional 25 g in twin pregnancies.

Sources: Institute of Medicine. (2002). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. Washington, DC: National Academies Press; Institute of Medicine. (2003). Dietary reference intakes: Applications in dietary planning. Washington, DC: National Academies Press; Institute of Medicine. (2004). Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. Washington, DC: National Academies Press.

Energy Needs

Energy (kilocalories or kcal) needs are met by carbohydrate, fat, and protein in the diet. No specific recommendations exist for the amount of carbohydrate and fat in the diet of the pregnant woman. However, intake of these nutrients should be adequate to support the recommended weight gain. Although protein can be used to supply energy, its primary role is to provide amino acids for the synthesis of new tissues (see the discussion later in this chapter). The estimated energy expenditure for the first trimester is the same as in the prepregnant state; during the second trimester of pregnancy the RDA is 340 kcal greater than the prepregnancy needs, and during the third trimester the amount is 462 kcal more than the prepregnant need (Institute of Medicine, 2003). Longitudinal assessment of weight gain during pregnancy is the best way to determine whether the kcal intake is adequate. Very underweight or active women or those with multifetal gestations will require more than the recommended increase in kcal to sustain the desired rate of weight gain.

Weight gain

The optimal weight gain during pregnancy is not known precisely. However, the amount of weight gained by the mother during pregnancy has an important bearing on the course and outcome of pregnancy. Adequate weight gain does not necessarily indicate that the diet is nutritionally adequate, but it is associated with a reduced risk of giving birth to a small-for-gestational-age (SGA) or preterm infant.

The desirable weight gain during pregnancy varies among women. The primary factor to consider in making a weight gain recommendation is the appropriateness of the prepregnancy weight for the woman’s height. Maternal and fetal risks in pregnancy are increased when the mother is either significantly underweight or overweight before pregnancy and when weight gain during pregnancy is either too low or too high. Severely underweight women are more likely to have preterm labor and to give birth to LBW infants. Women with inadequate weight gain have an increased risk of giving birth to an infant with intrauterine growth restriction (IUGR). Greater-than-expected weight gain during pregnancy may occur for many reasons, including multiple gestation, edema, preeclampsia, and overeating. Obesity (either preexisting or developed during pregnancy) increases the likelihood of macrosomia and fetopelvic disproportion; operative birth; emergency cesarean birth; postpartum hemorrhage; wound, genital tract, or urinary tract infection; birth trauma; and late fetal death. Obese women are more likely than normal-weight women to have gestational hypertension and gestational diabetes; their risk of giving birth to a child with a major congenital defect is double that of normal-weight women.

A commonly used method of evaluating the appropriateness of weight for height is the body mass index (BMI), which is calculated by the following formula:



where the weight is in kilograms and height is in meters. Therefore for a woman who weighed 51 kg before pregnancy and is 1.57 m tall:



Prepregnant BMI can be classified into the following categories: less than 18.5, underweight or low; 18.5 to 24.9, normal; 25 to 29.9, overweight or high; and greater than 30, obese (

For women with single fetuses, current recommendations are that women with a normal BMI should gain 11.3-15.9 kg during pregnancy, underweight women should gain 12.7-18.1 kg, overweight women should gain 6.8-11.3 kg, and obese women should gain 5.0-9.1 kg (Institute of Medicine, 2009). Adolescents are encouraged to strive for weight gains at the upper end of the recommended range for their BMI because the fetus and the still-growing mother apparently compete for nutrients. The risk of mechanical complications at birth is reduced if the weight gain of short adult women (shorter than 157 cm) is near the lower end of their recommended range.

Pattern of weight gain

Weight gain should take place throughout pregnancy. The risk of giving birth to an SGA infant is greater when the weight gain early in pregnancy has been poor. The likelihood of preterm birth increases when the gains during the last half of pregnancy have been inadequate. These risks exist even when the total gain for the pregnancy is in the recommended range.

The optimal rate of weight gain depends on the stage of pregnancy. During the first and second trimesters, growth takes place primarily in maternal tissue; during the third trimester, growth occurs primarily in fetal tissues. During the first trimester the average total weight gain is only 1 to 2.5 kg. Thereafter the recommended weight gain increases to approximately 0.4 kg per week for a woman of normal weight. The recommended weekly weight gain for overweight women during the second and third trimesters is 0.3 kg and for underweight women is 0.5 kg.

In twin gestations the recommended weight gain for women in the normal BMI category is 16.8 to 24.5 kg, for women who are overweight, 14.1 to 22.7 kg, and for obese women 11.3 to 19.1 kg (Institute of Medicine, 2009). The ideal weight gain for higher multiples is likely to be greater, but no specific recommendations have been issued (Malone & D’Alton, 2009).

The recommended caloric intake corresponds to this pattern of gain. For the first trimester, no increment is necessary; during the second and third trimesters an additional 340 kcal per day and 462 kcal per day, respectively, over the prepregnant intake is recommended. The amount of food that provides the needed increase is not great. The 340 additional kcal needed during the second trimester can be provided by one additional serving from any one of the following groups: milk, yogurt, or cheese (all skim milk products); fruits; vegetables; and bread, cereal, rice, or pasta.

The reasons for an inadequate weight gain (less than 1 kg per month for normal-weight women or less than 0.5 kg/month for obese women during the last two trimesters) or excessive weight gain (more than 3 kg per month) should be evaluated thoroughly. Possible reasons for deviations from the expected rate of weight gain, besides inadequate or excessive dietary intake, include measurement or recording errors, differences in weight of clothing, time of day, and accumulation of fluids. An exceptionally high gain is likely to be caused by an accumulation of fluids, and a gain of more than 3 kg in a month, especially after the twentieth week of gestation, often indicates the development of gestational hypertension.

Hazards of restricting adequate weight gain

Figure-conscious women can have difficulty making the transition from guarding against weight gain before pregnancy to valuing weight gain during pregnancy. In counseling these women the nurse can emphasize the positive effects of good nutrition, as well as the adverse effects of maternal malnutrition (demonstrated by poor weight gain) on infant growth and development. This counseling includes information on the components of weight gain during pregnancy (Table 8-2) and the amount of this weight that will be lost at birth. Because lactation can help to reduce maternal energy stores gradually, this discussion provides an opportunity to promote breastfeeding.

In the United States, 20% of women who give birth are obese (Paul, 2008). However, pregnancy is not a time for weight-reduction. Even overweight or obese pregnant women need to gain at least enough weight to equal the weight of the products of conception (fetus, placenta, and amniotic fluid). If overweight women limit their caloric intake to prevent weight gain, they may also excessively limit their intake of important nutrients. Moreover, dietary restriction results in catabolism of fat stores, which, in turn, augments the production of ketones. The long-term effects of mild ketonemia during pregnancy are not known, but ketonuria has been found to be correlated with the occurrence of preterm labor. The idea that the quality of the weight gain is important should be stressed to obese women (and to all pregnant women), with emphasis placed on the consumption of nutrient-dense foods and the avoidance of empty-calorie foods.

Weight gain is important, but pregnancy is not an excuse for uncontrolled dietary indulgence. Excessive weight gained during pregnancy may be difficult to lose after pregnancy, thus contributing to chronic overweight or obesity, an etiologic factor in a host of chronic diseases, including hypertension, diabetes mellitus, and arteriosclerotic heart disease. The woman who gains 18 kg or more during pregnancy is especially at risk (Box 8-1 and the Critical Thinking/Clinical Decision Making Box).


Protein, with its essential constituent nitrogen, is the nutritional element basic to growth. Adequate protein intake is essential to meet increasing demands in pregnancy. These demands arise from the rapid growth of the fetus; the enlargement of the uterus and its supporting structures, mammary glands, and placenta; an increase in maternal circulating blood volume and subsequent demand for increased amounts of plasma protein to maintain colloidal osmotic pressure; and the formation of amniotic fluid.

Milk, meat, eggs, and cheese are complete-protein foods with a high biologic value. Legumes (dried beans and peas), whole grains, and nuts are also valuable sources of protein. In addition, these protein-rich foods are a source of other nutrients such as calcium, iron, and B vitamins; plant sources of protein often provide needed dietary fiber. The recommended daily food plan (Table 8-3) is a guide to the amounts of these foods that would supply the quantities of protein needed. The recommendations provide for only a modest increase in protein intake over the prepregnant levels in adult women.

Protein intake in many people in the United States is relatively high, thus many women may not need to increase their protein intake at all during pregnancy. Three servings of milk, yogurt, or cheese (four for adolescents) and 5 to 6 oz (140 to 168 g) (two servings) of meat, poultry, or fish supply the recommended protein for the pregnant woman. Additional protein is provided by vegetables and breads, cereals, rice, and pasta. Pregnant adolescents, women from impoverished backgrounds, and women adhering to unusual diets, such as a macrobiotic (highly restricted vegetarian) diet, are those most likely to have inadequate protein intake. The use of high-protein supplements is not recommended because they have been associated with an increased incidence of preterm births. When choosing fish, pregnant and nursing women should be especially careful to select those that are low in mercury.


Essential during the exchange of nutrients and waste products across cell membranes, water is the main substance of cells, blood, lymph, amniotic fluid, and other vital body fluids. It also aids in maintaining body temperature. A healthy fluid intake promotes good bowel function; constipation is sometimes a problem during pregnancy. The recommended daily intake of fluid is approximately six to eight glasses (1500-2000 ml). Water, milk, and juices are good fluid sources. Dehydration may increase the risk of cramping, contractions, and preterm labor.

Caffeine in moderate amounts has not been proved to cause adverse effects during pregnancy. However, women who consume more than 300 mg of caffeine daily (equivalent to approximately 3 cups of coffee) may be at increased risk of miscarriage and of giving birth to infants with IUGR. The ill effects of caffeine have been proposed to result from vasoconstriction of the blood vessels supplying the uterus or from interference with cell division in the developing fetus. Consequently, caffeine-containing products such as caffeinated coffee, tea, soft drinks, and cocoa beverages should be avoided or consumed only in limited quantities.

No adverse effects on the normal mother or fetus have been found with the use of aspartame (NutraSweet, Equal), acesulfame potassium (Sunett), and sucralose (Splenda), artificial sweeteners commonly used in low- or no-calorie beverages and low-calorie food products. Aspartame, which contains phenylalanine, should be avoided by the woman with PKU (Box 8-2). Stevia (stevioside) is a food additive used as a sweetener but it has not been approved by the U.S. Food and Drug Administration (FDA) for that purpose.

BOX 8-2   Use of Artificial Sweeteners during Pregnancy

All of the following sweeteners are approved for use in all age groups, including pregnant women, in the United States:

Acesulfame K





Sugar alcohols (not technically artificial sweeteners; contain almost as many calories as sugar)

Sugar is important for the volume and moisture of baked goods. Artificial sweeteners may produce a good-tasting product, but some sugar is necessary in many recipes to yield normal volume and texture.


Minerals and Vitamins

In general, the nutrient needs of pregnant women, except perhaps the need for folate and iron, can be met through dietary sources. Counseling about the need for a varied diet rich in vitamins and minerals should be a part of every pregnant woman’s early prenatal care and should be reinforced throughout pregnancy. Supplements of certain nutrients (listed in the following discussion) are recommended whenever the woman’s diet is very poor or whenever significant nutritional risk factors are present. Nutritional risk factors in pregnancy are listed in Box 8-3.

Oct 8, 2016 | Posted by in NURSING | Comments Off on Maternal and Fetal Nutrition

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