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Course Sample:
This module provides an overview of nutrition considerations during pregnancy to assist the health professional when assessing the nutrition status of pregnant women and providing them with nutrition information and guidance. Resources are suggested for additional information on various topics, including nutrition assessment and counseling.
Pregnancy is a time when good nutrition is a key factor influencing the health of mother and child. Pregnancy may be the time in life when nutrition intervention produces the greatest health benefits. Considerable scientific evidence shows that diet is related to pregnancy outcome and frequency of complications. Diet and nutrition are factors that, in addition to supporting growth and health during pregnancy, can reduce health risks for mother and child during pregnancy and after delivery. Conversely, sub-optimal nutrition and physiologic conditions before and during pregnancy may impair fetal growth and lead to health consequences as the offspring reaches adulthood (Prentice & Goldberg, 2000).
According to the American Dietetic Association?s position statement, "Nutrition and Lifestyle for a Healthy Pregnancy Outcome" (American Dietetic Association [ADA], 2002, p. 1479):
?women of childbearing potential should maintain good nutritional status through a lifestyle that optimizes maternal health and reduces the risk of birth defects, suboptimal fetal growth and development, and chronic health problems in their children. The key components of a health-promoting lifestyle during pregnancy include appropriate weight gain; consumption of a variety of foods in accordance with the Food Guide Pyramid; appropriate and timely vitamin and mineral supplementation; avoidance of alcohol, tobacco, and other harmful substances; and safe food-handling. In particular for medical nutrition therapy, pregnant woman with inappropriate weight gain, hyperemesis, poor dietary patterns, phenylketonuria (PKU), certain chronic health problems, or a history of substance abuse should be referred to a qualified dietetics professional.
Impact of Nutrition on Pregnancy Outcomes
Pregnancy is a dynamic, anabolic state. Within several weeks of conception, a new endocrine organ, the placenta, has formed and is producing hormones that affect nutrient metabolism. These adjustments in nutrient metabolism, in addition to changes in the anatomy and physiology of the mother, support fetal growth and development while maintaining maternal homeostasis and preparing for lactation.
During pregnancy, vitamins, minerals, and proteins are transferred to the fetus through the mother?s blood. These nutrients are supplied by the mother?s nutrient reserves and dietary intake during pregnancy. If a mother?s diet cannot supply the nutritional needs of the infant, her own stores may be depleted. Deficiency of certain nutrients in the diet can lead to such adverse effects as anemia and neural tube defects.
General Nutrition Needs and Recommendations
The reproductive cycle is a continuum: A woman?s nutrition status at the time she conceives influences the course and outcome of her pregnancy in terms of health and well-being, and her nutrition during pregnancy influences preparation for lactation. For optimal health outcomes of both mother and child, women should begin their pregnancies in good nutrition status. Therefore, appropriate information and advice needs to reach women before they become pregnant, and well as during prenatal and postpartum care (ADA, 2002).
During pregnancy, several physiological changes occur that increase nutrient requirements and absorption. Beginning in the third month, metabolic and blood circulation rates increase, allowing nutrients to reach the fetus and creating an increase in demand for nutrients. During pregnancy, the body uses nutrients more efficiently. The kidneys, intestines, and other organs are working harder to absorb nutrients, increasing the mother?s ability to nourish the fetus.
Eating a well-balanced diet consisting of a variety of nutrient-dense foods ensures that both mother and fetus receive needed nutrients. Although an increase in calories is necessary during pregnancy, it is important that the calories contain adequate nutrients for optimal growth and health. Table 1 shows the number of servings from each of the food groups for three different calorie levels that are recommended by the USDA (United States Department of Agriculture) to ensure adequate nutrient intake.
However, many women of childbearing age in the United States do not maintain good nutritional status before, during, and after pregnancy (ADA, 2002). Poor nutrition status is the most common cause of fetal growth retardation. Severe malnutrition produces its most marked effects when present in the last half to the last third of pregnancy (Snetselaar, 1989).
The number of food group servings consumed by pregnant women have been calculated from the Third National Health and Nutrition Examination Survey 1988-94 (NHANES III) as a part of the calculation of Healthy Eating Index (HEI) scores. Figure 1 shows the average number of food group servings consumed by pregnant women in NHANES III: those participating in the WIC (USDA Special Supplemental Nutrition Program for Women, Infants, and Children) program, those not participating in WIC with income less than 185% of nationally adjusted Federal poverty level (the cut-off value for participation in WIC programs), and those with income above 185% of the poverty level. The above poverty group ate significantly more vegetables (3.1 servings) than the non-WIC below poverty group (2.1 servings). WIC participants consumed significantly fewer servings of milk (2.3) than the above poverty pregnant women (3.2 servings). For fruits and vegetables, the WIC participants appear more comparable to the above poverty group and consume more than the non-WIC below poverty group (USDA Center for Nutrition Policy and Promotion, 2000).
To examine the nutrient status of participants of the WIC program, dietary intake was assessed by the USDA Center for Nutrition Policy and Promotion (CNPP). The study, called the "Review of the Nutritional Status of WIC Participants 1999", revealed that pregnant and post-partum women were not consuming the recommended amount of several important nutrients, including iron, calcium, folic acid, zinc, and magnesium (USDA Center for Nutrition Policy and Promotion, 2000).
Energy
Energy requirements during pregnancy increase because of increases in basal energy expenditure (BEE), activity, and energy deposition in fetal and maternal tissues. During pregnancy, BEE increases due to the metabolic processes of the uterus and the fetus and the increased work of the heart and lungs. The increase is BEE is one of the major increases in energy requirements during pregnancy. The energy needs of the fetus, uterus, placenta, and mammary glands comprise only 15% of the total energy requirement, while the remainder supports energy needs for maintenance, work, and maternal fat deposition.
Differences in energy requirements between individuals (due to differences in blood volume, fetal and uterine tissues, and muscle mass) make it difficult to set standards for energy intake. In late pregnancy, about one half of the increase in energy expenditure is due to the fetus. The estimated energy requirement (EER) for pregnancy in the first trimester is the same as the EER for non-pregnant women; in the second trimester, it is the EER + approximately 350 calories; and in the third trimester, it is the EER + approximately 450 calories (Institute of Medicine of the National Academies [IOM], 2002). The total energy need during pregnancy ranges between 2,500 and 2,700 calories per day for most women. However, pre-pregnant body mass index (BMI), maternal age, rate of weight gain, and appetite must be considered in tailoring this recommendation to individuals (ADA, 2002). For instance, for normal and overweight women in developed countries, the additional energy need may be less than 300 calories per day, especially in sedentary women. Appropriate weight gain and appetite are better indicators of energy sufficiency than the amount of calories consumed (ADA, 2002).
Protein
Protein requirements increase during pregnancy because of protein deposition and the increase in protein turnover during the second and third trimesters of pregnancy. Approximately 925 grams of protein is accumulated during pregnancy, including the protein components of the fetus, uterus, expanded maternal blood volume, placenta, extracellular fluid, and amniotic fluid. There is also evidence additional maternal protein-containing tissues exist, probably in skeletal muscle (IOM, 2002).
Dietary protein is needed to support the growth of maternal and fetal tissues. The RDA for protein during pregnancy for all age groups is 71 grams per day (1.1 g/kg/day) or 25 grams in addition to prepregnancy requirements. Although there are no studies investigating dietary protein intervention in twin pregnancies, women carrying twins most likely have higher protein needs, therefore, the IOM recommends an additional 50 grams of protein intake per day (i.e. 96 grams of protein per day, total) during twin pregnancies from the second trimester on (IOM, 2002).
Fat
Total Fat
Dietary fat is an energy source and a source of n-6 and n-3 polyunsaturated fatty acids. Dietary fat increases absorption of fat soluble vitamins and precursors such as vitamin A and pro-vitamin A carotenoids.
The amount of fat in the diet can range from 10% to 50% of total calories without differing effects on short-term health. Several studies have reported the link between low- and high-fat diets and the indicators for and risk of chronic diseases such as coronary heart disease, diabetes, and obesity. The data is insufficient, however, to determine the amount of intake of dietary fat to maintain fat balance or prevent chronic diseases (IOM, 2002).
Saturated Fatty Acids
There is no evidence to indicate that dietary saturated fatty acids are essential or have a positive effect on chronic disease prevention, therefore, intake recommendations have not been set (IOM, 2002).
Monounsaturated Fatty Acids
Sources of monounsaturated fats include olive oil, canola oil, peanut oil, avocado, peanut butter, nuts, and seeds. Monounsaturated fatty acids help lower LDL cholesterol when substituted for foods high in saturated fat. However, according to the Institutes of Medicine (2002), because there is no evidence that monounsaturated fatty acids are essential in the diet and because monounsaturated fatty acids have no known independent role in preventing chronic diseases, a recommendation for dietary intake has not been set.
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