Understanding Normal and Clinical Nutrition by Sharon Rady Rolfes Kathryn Pinna Ellie Whitney (z-lib.org)(13)(1).pdf

14 Learning gPS 14-1 nutrition Prior to Pregnancy 442 Life Cyc...

14 Learning gPS 14-1 nutrition Prior to Pregnancy 442 Life Cycle Nutrition: Learn iT List the ways men and women can prepare for a healthy pregnancy. 14-2 growth and Development during Pregnancy 443 Pregnancy Learn iT Describe fetal development from conception to birth and explain how maternal malnutrition can affect critical periods. Placental Development 443 Fetal growth and Development 443 and Lactation Critical Periods 444 14-3 Maternal Weight 448 Learn iT Explain how both underweight and overweight can interfere with a healthy pregnancy and how weight gain and physical activity can support maternal health and infant growth. Weight Prior to Conception 448 Weight gain during Pregnancy 448 Nutrition in Your Life exercise during Pregnancy 450 14-4 nutrition during Pregnancy 451 Food choices have consequences. Sometimes they are immediate, such as when Learn iT Summarize the nutrient needs of you get heartburn after eating a pepperoni pizza. Other times they sneak up on women during pregnancy. you, such as when you gain weight after repeatedly overindulging in hot fudge energy and nutrient needs during sundaes. Quite often, they are temporary and easily resolved, such as when Pregnancy 452 hunger pangs strike after you skip lunch. During pregnancy, however, the conse- Vegetarian Diets during Pregnancy and quences of a woman’s food choices are dramatic. They affect not only her health, Lactation 455 but also the growth and development of another human being—and not just for Common nutrition-related Concerns today, but for years to come. Making smart food choices is a huge responsibil- of Pregnancy 455 ity, but fortunately, it’s fairly simple. In the Nutrition Portfolio at the end of this 14-5 High-risk Pregnancies 456 chapter, you can determine how well your current diet might support the needs Learn iT Identify factors predicting low-risk of a pregnant woman. and high-risk pregnancies and describe ways to manage them. The infant’s Birthweight 457 Malnutrition and Pregnancy 457 Food assistance Programs 458 Maternal Health 458 Each person enters this world with a unique genetic map that determines the The Mother’s age 460 primary ways that person’s physical and mental characteristics will develop Practices incompatible with Pregnancy 461 throughout life. Some of those characteristics cannot be changed, but others 14-6 nutrition during Lactation 464 can be influenced within genetically defined limits. One of several ways to Learn iT Summarize the nutrient needs of women during lactation. ensure the optimal growth, maintenance, and health of the body is through Lactation: a Physiological Process 464 proper nutrition. Ideally, a person’s diet supplies sufficient amounts of all the Breastfeeding: a Learned Behavior 465 Maternal energy and nutrient needs during nutrients to meet the needs incurred by the physiological demands of preg- Lactation 465 nancy, lactation, growth, and aging. Maternal Health 467 All people—pregnant and lactating women, infants, children, adolescents, Practices incompatible with Lactation 468 and adults—need the same nutrients, but the amounts they need vary de- Highlight 14 Fetal Alcohol Syndrome 473 pending on their stage of life. This chapter focuses on nutrition in preparation Learn iT Explain how drinking alcohol endangers the fetus and how women can prevent for, and support of, pregnancy and lactation. The next two chapters address fetal alcohol syndrome. the needs of infants, children, adolescents, and older adults. 441 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  14-1 nutrition Prior to Pregnancy ❯ LEARN IT List the ways men and women can prepare for a healthy pregnancy. Both a man’s and a woman’s nutrition may affect fertility and possibly the ge- netic contributions they make to their children, but it is the woman’s nutrition that has the most direct influence on the developing fetus.1 Her body provides the environment for the growth and development of a new human being. Prior Stockbyte/Jupiter Images to pregnancy, however, both men and women have a unique opportunity to pre- pare physically, mentally, and emotionally for the many changes to come. 2 In preparation for a healthy pregnancy, they can establish the following habits: Achieve and maintain a healthy body weight. Both underweight and over- PHoTo 14-1 Young adults can prepare weight are associated with infertility. Overweight and obese men have low for a healthy pregnancy by taking care of sperm counts and hormonal changes that reduce fertility.3 Excess body fat themselves today. in women disrupts menstrual regularity and ovarian hormone produc- tion.4 Should a pregnancy occur, mothers, both underweight and over- weight, and their newborns, face increased risks of complications. Choose an adequate and balanced diet. Malnutrition reduces fertility and im- pairs the early development of an infant should a woman become pregnant. In contrast, a healthy diet that includes a full array of vitamins and miner- als can favorably influence fertility.5 Men with diets rich in antioxidant nu- trients and low in saturated fats have higher sperm numbers and motility.6 Be physically active. A woman who wants to be physically active when she is pregnant needs to become physically active beforehand. Receive regular medical care. Regular health care visits help ensure a healthy start to pregnancy. Manage chronic conditions. Conditions such as diabetes, hypertension, HIV/ AIDS, phenylketonuria (PKU), and sexually transmitted diseases can adversely affect a pregnancy and need close medical attention to help en- sure a healthy outcome. Avoid harmful influences. Both maternal and paternal ingestion of, or expo- sure to, harmful substances (such as cigarettes, alcohol, drugs, or environ- mental contaminants) can cause miscarriage or abnormalities, alter genes or their expression, and may interfere with fertility.7 Young adults who nourish and protect their bodies do so not only for their own sakes, but also for future generations (see Photo 14-1). > Die Ta ry guiDeL ine S F or a MeriC a nS 2 0 15 – 2 0 2 0 Before becoming pregnant, women are encouraged to: Achieve and maintain a healthy weight. Choose foods containing heme iron, which is more readily absorbed by the body, ad- ditional iron sources (such as legumes and dark green vegetables as well as fortified foods such as bread and ready-to-eat cereals), and enhancers of iron absorption (such as vitamin C–rich foods). Consume 400 micrograms per day of synthetic folate from fortified foods and/or supplements in addition to folate from a varied diet. ❯ REVIEW IT List the ways men and women can prepare for a healthy pregnancy. Prior to pregnancy, the health and behaviors of both men and women can influence fertility and fetal development. In preparation, they can achieve and maintain a healthy body weight, fertility: the capacity of a woman to produce a normal ovum periodically and of a man to produce normal sperm; the ability choose an adequate and balanced diet, be physically active, receive regular medical care, to reproduce. manage chronic diseases, and avoid harmful influences. 442 Chapter 14 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203 14-2 growth and Development during Pregnancy ❯LEARN IT Describe fetal development from conception to birth and explain how maternal malnutrition can affect critical periods. A whole new life begins at conception. Organ systems develop rapidly, and nu- trition plays many supportive roles. This section describes placental development and fetal growth, paying close attention to times of intense developmental activity. Placental Development In the early days of pregnancy, a spongy structure known as the placenta develops in the uterus. Two associated structures also form (see Figure 14-1). One is the amniotic sac, a fluid-filled balloonlike struc- conception: the union of the male sperm and the female ture that houses the developing fetus. The other is the umbilical cord, a ropelike ovum; fertilization. structure containing fetal blood vessels that extends through the fetus’s “belly placenta (plah-SEN-tuh): the organ that develops inside button” (the umbilicus) to the placenta. These three structures play crucial roles the uterus early in pregnancy, through which the fetus during pregnancy, and then are expelled from the uterus during childbirth. receives nutrients and oxygen and returns carbon dioxide and other waste products to be excreted. The placenta develops as an interweaving of fetal and maternal blood vessels em- uterus (YOU-ter-us): the muscular organ within which the bedded in the uterine wall. The maternal blood transfers oxygen and nutrients to infant develops before birth. the fetus’s blood and picks up fetal waste products. By exchanging oxygen, nutrients, amniotic (am-nee-OTT-ic) sac: the “bag of waters” in the and waste products, the placenta performs the respiratory, absorptive, and excretory uterus, in which the fetus floats. functions that the fetus’s lungs, digestive system, and kidneys will provide after birth. umbilical (um-BILL-ih-cul) cord: the ropelike structure The placenta is a versatile, metabolically active organ. Like all body tissues, through which the fetus’s veins and arteries reach the placenta; the route of nourishment and oxygen to the fetus the placenta uses energy and nutrients to support its work. It produces an array and the route of waste disposal from the fetus. The scar in of hormones that maintain pregnancy and prepare the mother’s breasts for lac- the middle of the abdomen that marks the former attachment tation (making milk). A healthy placenta is essential for the developing fetus to of the umbilical cord is the umbilicus (um-BILL-ih-cus), commonly known as the “belly button.” attain its full potential.8 ovum (OH-vum): the female reproductive cell, capable of Fetal growth and Development Fetal development begins with the fer- developing into a new organism upon fertilization; commonly referred to as an egg. tilization of an ovum by a sperm. Three stages follow: the zygote, the embryo, sperm: the male reproductive cell, capable of fertilizing an and the fetus (see Figure 14-2, p. 444). ovum. Figure 14-1 The Placenta and associated Structures To understand how placental villi absorb nutrients without maternal and fetal blood interacting directly, think of how the intestinal villi work. The GI side of the intesti- nal villi is bathed in a nutrient-rich fluid (chyme). The intestinal villi absorb the nutrient molecules and release them into the body via capillaries. Similarly, the maternal side of the placental villi is bathed in nutrient-rich maternal blood. The placental villi absorb the nutrient molecules and release them to the fetus via fetal capillaries. The arrows indicate the direction of blood flow. Pool of mother’s blood Fetal vein Fetal artery Fingerlike projections (called placental villi) Umbilical cord contain fetal blood vessels Uterine wall and extend into the pool of mother’s blood. No actual Placenta mingling of fetal and maternal blood occurs, but substances pass back and forth. Thus, oxygen and nutrients Umbilical cord from the mother’s blood Umbilical vein enter fetal vessels, and waste products are removed. Umbilical arteries Mother’s veins carry Amniotic fetal wastes away. sac In the placenta, maternal blood vessels lie side by side with fetal blood Mother’s arteries bring vessels that reach the fresh blood with oxygen fetus through the and nutrients to the fetus. umbilical cord. Fetal portion Maternal portion of placenta of placenta Life Cycle nutrition: Pregnancy and Lactation 443 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  FigurE 14-2 Stages of Embryonic and Fetal Development 1 A newly fertilized ovum is 3 A fetus after 11 weeks called a zygote and is about of development is just over the size of the period at the an inch long. Notice the end of this sentence. Less umbilical cord and blood than 1 week after fertilization, vessels connecting the these cells have rapidly fetus with the placenta. Petit Format/ Nestle/Science Source divided multiple times to become a blastocyst ready for implantation. Petit Format/ Nestle/ Science Source 2 After implantation, the 4 A newborn infant after placenta develops and begins 9 months of development to provide nourishment to the measures close to 20 inches developing embryo. An in length. From 8 weeks to embryo 5 weeks after term, this infant grew 20 fertilization is about 1/2 inch times longer and 50 times long. heavier. Petit Format/ Nestle/ Science Source Cindy Vannelli The Zygote The newly fertilized ovum is called a zygote. It begins as a single cell and rapidly divides to become a blastocyst. During that first week, the blastocyst floats down into the uterus, where it will embed itself in the inner uterine wall— a process known as implantation. Cell division continues at an amazing rate as each set of cells divides into many other cells. The Embryo At first, the number of cells in the embryo doubles approximately every 24 hours; later the rate slows, and only one doubling occurs during the final 10 weeks of pregnancy. At 8 weeks, the 1¼-inch embryo has a complete cen- tral nervous system, a beating heart, a digestive system, well-defined fingers and toes, and the beginnings of facial features. The Fetus The fetus continues to grow during the next 7 months. Each organ grows to maturity according to its own schedule, with greater intensity at some times than at others. As Figure 14-2 shows, fetal growth is phenomenal: weight zygote (ZY-goat): the initial product of the union of ovum increases from less than an ounce to about 7½ pounds (3500 grams). Most suc- and sperm; a fertilized ovum. cessful pregnancies are full term—defined as births occurring at 39 through blastocyst (BLASS-toe-sist): the developmental stage 40 weeks—and produce a healthy infant weighing 6½ to 8 pounds.9 of the zygote when it is about 5 days old and ready for implantation. implantation (IM-plan-TAY-shun): the embedding of the Critical Periods Times of intense development and rapid cell division are blastocyst in the inner lining of the uterus. called critical periods—critical in the sense that those cellular activities can occur embryo (EM-bree-oh): the developing infant from 2 to only at those times. If cell division and number are limited during a critical period, 8 weeks after conception. full recovery is not possible (see Figure 14-3). Damage during these critical times fetus (FEET-us): the developing infant from 8 weeks after of pregnancy has permanent consequences for the life and health of the fetus.10 conception until term. The development of each organ and tissue is most vulnerable to adverse in- full term: births occurring at 39 through 40 weeks of fluences (such as nutrient deficiencies or toxins) during its own critical period gestation. (see Figure 14-4). The neural tube, for example, is the structure that eventually critical periods: finite periods during development in which certain events occur that will have irreversible effects on becomes the brain and the spinal cord, and its critical period of development later developmental stages; usually a period of rapid cell is from 17 to 30 days of gestation. Consequently, neural tube development is division. most vulnerable to nutrient deficiencies, nutrient excesses, or toxins during this gestation (jes-TAY-shun): the period from conception critical time—when most women do not yet even realize they are pregnant. Any to birth. For human beings, the average length of a healthy gestation is 40 weeks. Pregnancy is often divided into abnormal development of the neural tube or its failure to close completely can 3-month periods, called trimesters. cause a major defect in the central nervous system. 444 Chapter 14 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  Figure 14-3 The Concept of Critical Figure 14-4 Critical Periods of Development Periods in Fetal Development During embryonic development (from 2 to 8 weeks), many of the tissues are in their criti- Critical periods occur early in fetal development. An ad- cal periods (purple area of the bars); events occur that will have irreversible effects on the verse influence felt early in pregnancy can have a much development of those tissues. In the later stages of development (green area of the bars), more severe and prolonged impact than one felt later on. the tissues continue to grow and change, but the events are less critical in that they are relatively minor or reversible. Key: Critical development An adverse influence felt Continued development late temporarily impairs development, but a full recovery is possible. Central nervous system Heart Ears Normal Eyes development Tissue Legs and arms Teeth Palate External genitalia An adverse influence 0 2 4 8 12 16 Term felt early permanently Embryo Fetus impairs development, and a full recovery Weeks of gestation never occurs. SOURCE: Adapted from Before We Are Born: Essentials of Embryology and Birth Defects by K. L. Moore and T.V.N. Persaud (W. B. Saunders, 2003). Time Critical period neural Tube Defects Each year in the United States, approximately 3000 preg- nancies are affected by a neural tube defect—a malformation of the brain, spinal cord, or both during embryonic development.* The two most common types of neural tube defects are anencephaly (no brain) and spina bifida (split brain). In anencephaly, the upper end of the neural tube fails to close. Consequently, the brain is either missing or fails to develop. Pregnancies affected by anencephaly often end in miscarriage; infants born with anencephaly die shortly after birth. Spina bifida is characterized by incomplete closure of the spinal cord and its bony encasement (see Figure 14-5, p. 446). The meninges membranes covering the spinal cord often protrude as a sac, which may rupture and lead to meningi- tis, a life-threatening infection. Spina bifida is accompanied by varying degrees of paralysis, depending on the extent of the spinal cord damage. Mild cases may not even be noticed, but severe cases lead to death. Common problems include neural tube defect: malformations of the brain, spinal cord, clubfoot, dislocated hip, kidney disorders, curvature of the spine, muscle weak- or both during embryonic development that often results in ness, mental impairments, and motor and sensory losses. lifelong disability or death. The cause of neural tube defects is unknown, but researchers are examining anencephaly (AN-en-SEF-a-lee): an uncommon and always fatal type of neural tube defect, characterized by the several gene-gene, gene-nutrient, and gene-environment interactions. A preg- absence of a brain. nancy affected by a neural tube defect can occur in any woman, but these factors an 5 not (without) make it more likely11: encephalus 5 brain A personal or family history of a neural tube defect spina (SPY-nah) bifida (BIFF-ih-dah): one of the most common types of neural tube defects, characterized by Maternal diabetes or gestational diabetes the incomplete closure of the spinal cord and its bony encasement. Maternal Hispanic ethnicity spina 5 spine *Worldwide, some 300,000 pregnancies are affected by neural tube defects each year. bifida 5 split Life Cycle nutrition: Pregnancy and Lactation 445 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  FiGure 14-5 Spina Bifida Spina bifida, a common neural tube defect, occurs when the vertebrae of the spine fail to close around the spinal cord, leaving it unpro- tected. The B vitamin folate—consumed prior to and during pregnancy—helps prevent spina bifida and other neural tube defects. Spina Bifida Normal Spine Vertebra Meninges Spinal cord Spinal fluid Spine Spine Maternal use of certain antiseizure medications Inadequate folate Maternal obesity Not all cases of neural tube defects can be prevented, but folate supplementation greatly reduces the incidence and severity.12 Folate Supplementation Chapter 10 describes how folate supplements taken 1 month before conception and continued throughout the first trimester can help support a healthy pregnancy, prevent neural tube defects, and reduce the severity of defects that do occur. For this reason, all women of childbearing age who are capable of becoming pregnant should consume 400 micrograms (0.4 milligrams) of folate daily. A woman who has previously had an infant with a neural tube defect may be advised by her physician to take folate supplements in doses ten times larger— 4 milligrams daily. Because high doses of folate can mask the symptoms of pernicious anemia associated with a vitamin B12 deficiency, quantities of 1 milligram or more re- quire a prescription. Most over-the-counter multivitamin-mineral supplements contain 400 micrograms of folate; prenatal supplements usually contain 800 micrograms. Because half of the pregnancies each year are unplanned and because neural tube defects occur early in development before most women realize they are preg- nant, grain products in the United States are fortified with folate to help ensure an adequate intake. Labels on fortified products may claim that an “adequate intake of folate has been shown to reduce the risk of neural tube defects.” Fortification has improved folate status in women of childbearing age and lowered the number of neural tube defects that occur each year, as shown in Figure 10-11 (p. 318). > Die ta ry GuiDel ine S F or a meriC a nS 2 0 15 – 2 0 2 0 Women who are pregnant are advised to consume 600 micrograms of dietary folate equivalents from all sources. 446 Chapter 14 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203 Fetal Programming Clearly, substances such as nutrients influence the growth and development of an infant, but recent genetic research is beginning to ex- plain how they might inf luence the infant’s development of obesity and dis- eases in adulthood. This process is commonly known as fetal programming, although “developmental origins of disease” may more appropriately describe the ever-changing interactions involved in disease development.13 In the case of pregnancy, the mother’s nutrition can change gene expression in the fetus.14 Such epigenetic changes during pregnancy can affect the infant’s development of obesity and related adult diseases.15 Some research suggests that these epigen- etic changes during pregnancy may even influence succeeding generations. (See Highlight 6 for further discussion of epigenetics.) Chronic Diseases Much research suggests that dietary inf luences at critical times during fetal development program the infant‘s future development, me- tabolism, and health.16 Maternal diet during pregnancy may alter the infant’s bodily functions by permanently changing an organ’s structure and resulting se- cretions, altering gene expression through epigenetics, or influencing the regula- tion of cellular aging.17 For example, undernutrition may limit liver growth and program lipid metabolism in such a way that the infant will develop risk factors for cardiovascular disease as an adult.18 Similarly, overnutrition and maternal obesity may program the fetus to develop chronic diseases later in life.19 On a positive note, a maternal diet rich in nutrients such as folate can have epigenetic effects that protect the developing fetus against some cancers into adulthood.20 (See Highlight 6 for a detailed discussion of epigenetics and folate’s role in meth- ylation reactions.) Malnutrition during the critical period of pancreatic cell growth provides an example of how type 2 diabetes may develop in adulthood. The pancreatic cells responsible for producing insulin (the beta cells) normally increase more than 130-fold between 12 weeks of gestation and 5 months after birth. Nutrition is a primary determinant of beta cell growth, and infants who have suffered prena- tal malnutrition have significantly fewer beta cells than well-nourished infants. They are also more likely to be low-birthweight infants—and low birthweight correlates with insulin resistance later in life.21 One hypothesis suggests that dia- betes may develop from the interaction of inadequate nutrition early in life (low birthweight) with abundant nutrition later in life (overweight adult): the small mass of beta cells developed in times of undernutrition during fetal development may be insufficient in times of overnutrition during adulthood when the body needs more insulin. Hypertension may develop from a similar scenario of inadequate growth dur ing placental and gestational development followed by accelerated growth during early childhood: the small mass of kidney cells developed dur- ing malnutrition may be insufficient to handle the excessive demands of later life. As adults, low-birthweight infants may be particularly sensitive to the blood- pressure raising effects of salt.22 ❯REVIEW IT Describe fetal development from conception to birth and explain how maternal malnutrition can affect critical periods. Maternal nutrition before and during pregnancy affects both the mother’s health and the infant’s growth. As the infant develops through its three stages—the zygote, embryo, and fetus—its organs and tissues grow, each on its own schedule. Times of intense development are critical periods that depend on nutrients to proceed smoothly. Without folate, for example, the neural tube fails to develop completely during the first month of pregnancy, prompting recommendations that all women of childbearing age take folate daily. Because critical periods occur throughout pregnancy, a woman should continu- ously take good care of her health. That care should include achieving and main- taining a healthy body weight prior to pregnancy and gaining sufficient weight fetal programming: the influence of substances during fetal during pregnancy to support a healthy infant. growth on the development of diseases in later life. Life Cycle nutrition: Pregnancy and Lactation 447 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  14-3 Maternal Weight ❯LEARN IT Explain how both underweight and overweight can interfere with a healthy pregnancy and how weight gain and physical activity can support maternal health and infant growth. Birthweight is the most reliable indicator of an infant’s health. As a later section of this chapter explains, compared with a normal-weight infant, an underweight infant is more likely to have physical and mental abnormalities, suffer illnesses, and die. In general, higher birthweights present fewer risks for infants. Two char- acteristics of the mother’s weight influence an infant’s birthweight: her weight prior to conception and her weight gain during pregnancy. Weight Prior to Conception A woman’s weight prior to conception inf luences fetal growth. Even with the same weight gain during pregnancy, underweight women tend to have smaller babies than heavier women. Ideally, Larry Williams/Corbis before a woman becomes pregnant, she will have established diet and activity habits to support an adequate, and not excessive, weight gain during pregnancy.23 underweight An underweight woman (BMI ,18.5) has a high risk of having a low-birthweight infant, especially if she is malnourished or unable to gain suf- ficient weight during pregnancy. In addition, the rates of preterm births and PHoTo 14-2 Fetal growth and maternal infant deaths are higher for underweight women. An underweight woman im- health depend on a sufficient weight gain proves her chances of having a healthy infant by gaining sufficient weight prior during pregnancy. to conception or by gaining extra pounds during pregnancy. To gain weight and ensure nutrient adequacy, an underweight woman can follow the dietary recom- mendations for pregnant women (described on pp. 452–455). overweight and obesity An estimated one-third of all pregnant women in the United States are obese (BMI $30), which can create problems related to preg- nancy, infancy, and childbirth.24 Obese women have an especially high risk of medical complications such as gestational hypertension, gestational diabetes, and postpartum infections. Compared with other women, obese women are also more likely to have other complications of labor and delivery. Complications in women after gastric bypass surgery are lower than in obese women, but their in- fants are more likely to be small, perhaps because of limited nutrient absorption; careful monitoring during pregnancy is advised.25 Infants of obese women are more likely to be large for gestational age, weighing more than 9 pounds.26 Problems associated with macrosomia include increases in the likelihood of a difficult labor and delivery, birth trauma, and cesarean delivery, which presents a high risk in obese women.27 Consequently, these in- fants have a greater risk of poor health and death than infants of normal weight. Of greater concern than infant birthweight is the poor development of infants born to obese mothers.28 Obesity may double the risk for neural tube defects. Folate’s role has been examined, but a more likely explanation seems to be poor glycemic control. Undiagnosed diabetes might also explain why obese women have a greater risk of giving birth to infants with heart defects and other abnormalities. Even moderate overweight increases the risks for some complications, such as preterm (premature): births occurring before 37 weeks of gestational hypertension, gestational diabetes, preterm births, and cesarean de- gestation; births occurring at 37 to 38 weeks of gestation are liveries; risks tend to increase as BMI increases.29 Health care providers have tra- designated early term. ditionally advised against weight-loss dieting during pregnancy. Limited research, macrosomia (mak-roh-SO-me-ah): abnormally large body size. In the case of infants, a birthweight at the 90th however, suggests that following a well-balanced, kcalorie-restricted diet and reg- percentile or higher for gestational age (roughly 9 lb—or ular exercise program can support a healthy pregnancy with little or no weight 4000 g—or more); macrosomia results from prepregnancy gain. Ideally, overweight and obese women will achieve a healthier body weight obesity, excessive weight gain during pregnancy, or uncontrolled gestational diabetes. before becoming pregnant and avoid excessive weight gain during pregnancy.30 macro 5 large soma 5 body Weight gain during Pregnancy Fetal growth and maternal health de- pend on a sufficient weight gain during pregnancy (see Photo 14-2). Maternal cesarean (si-ZAIR-ee-un) delivery: a surgically assisted birth involving removal of the fetus by an incision into the weight gain during pregnancy correlates closely with infant birthweight, which uterus, usually by way of the abdominal wall. is a strong predictor of the health and subsequent development of the infant.31 448 Chapter 14 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203 TaBLe 14-1 recommended Weight gains Based on Prepregnancy Weight recommended Weight gain Prepregnancy Weight For single birth For twin birth Underweight (BMI ,18.5) 28 to 40 lb Insufficient data to make (12.5 to 18.0 kg) recommendation Healthy weight (BMI 18.5 to 24.9) 25 to 35 lb 37 to 54 lb (11.5 to 16.0 kg) (17.0 to 25.0 kg) Overweight (BMI 25.0 to 29.9) 15 to 25 lb 31 to 50 lb (7.0 to 11.5 kg) (14.0 to 23.0 kg) Obese (BMI $30) 11 to 20 lb 25 to 42 lb (5.0 to 9.0 kg) (11.0 to 19.0 kg) SOURCE: Institute of Medicine, Weight Gain during Pregnancy: Reexamining the Guidelines (Washington, D.C.: National Academies Press, 2009). > Die Ta ry guiDeL ine S F or a MeriC a nS 2 0 15 – 2 0 2 0 Pregnant women are encouraged to gain weight within the gestational weight gain guidelines (see Table 14-1). recommended Weight gains Table 14-1 presents recommended weight gains for various prepregnancy weights. The recommended gain for a woman who begins pregnancy at a healthy weight and is carrying a single fetus is 25 to 35 pounds. An underweight woman needs to gain between 28 and 40 pounds; and an overweight woman, between 15 and 25 pounds. About one-third of US women gain weight within these recommended ranges; about half gain more than rec- ommended.32 Appropriate weight gains reduce complications, help women limit weight retention and gains after pregnancy, and help their infants prevent obesity during childhood.33 To limit excessive weight gains, pregnant women can select foods with a high nutrient density (nutrient per kcalorie) but a low energy density (kcalorie per gram). Physical activity also plays a key role in preventing excessive weight gains during pregnancy and minimizing weight retention after the birth.34 Weight-gain Patterns For the normal-weight woman, weight gain ideally follows a pattern of 3½ pounds during the first trimester and 1 pound per week thereaf- ter. Health care professionals monitor weight gain using a prenatal weight-gain grid (see Figure 14-6). Identifying inadequate or excessive weight gains by the second trimester allows sufficient time for adjustments in diet and activity.35 Figure 14-6 recommended Prenatal Weight gain Based on Prepregnancy Weight 40 40 40 36 36 36 32 32 32 Pounds gained Pounds gained Pounds gained 28 28 28 24 24 24 20 20 20 16 16 16 12 12 12 8 8 8 4 4 4 0 4 8 12 16 20 24 28 32 36 40 0 4 8 12 16 20 24 28 32 36 40 0 4 8 12 16 20 24 28 32 36 40 Weeks of gestation Weeks of gestation Weeks of gestation Normal-weight women should gain about Underweight women should gain about 5 Overweight women should gain about 2 31/2 pounds in the first trimester and just pounds in the first trimester and just over 1 pounds in the first trimester and 2/3 under 1 pound/week thereafter, achieving a pound/week thereafter, achieving a total gain pound/week thereafter, achieving a total gain total gain of 25 to 35 pounds by term. of 28 to 40 pounds by term. of 15 to 25 pounds. Life Cycle nutrition: Pregnancy and Lactation 449 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  Figure 14-7 Components of Weight gain during Pregnancy Weight gain (lb) Increase in breast size 2 Increase in mother’s 4 fluid volume Placenta 11/2 Increase in blood supply 4 to the placenta Amniotic fluid 2 Infant at birth 7 1/2 Increase in size of 2 uterus and supporting muscles Mother’s necessary 7 1st trimester 2nd trimester fat stores 3rd trimester 30 Components of Weight gain Women often express concern about the weight gain that accompanies a healthy pregnancy. They may find comfort by remember- ing that most of the gain supports the growth and development of the placenta, uterus, blood, and breasts, the increase in blood supply and fluid volume, as well as a healthy 7½-pound infant. A small amount goes into maternal fat stores, and even that fat has a special purpose—to provide energy for growth, labor, and lactation. Figure 14-7 shows the components of a healthy 30-pound weight gain. Weight Loss after Pregnancy The pregnant woman loses some weight at delivery. In the following weeks, she loses more as her blood volume returns to normal and she sheds accumulated fluids. Quite likely, her goal is to return to her pre- pregnancy weight, but that may depend in part on whether she stayed within the pregnancy weight gain recommendations. In general, the more weight a woman gains beyond the needs of pregnancy, the more she retains and the more likely she will continue to gain over the next several years.36 Even with an average weight gain during pregnancy, most women tend to retain a couple of pounds with each pregnancy.37 When those couple of pounds become several more, complications such as diabetes and hypertension in future pregnancies as well as chronic dis- eases in later life become more likely—even for women who are not overweight. Those who are successful in losing their pregnancy weight are more likely to limit weight gains through middle adulthood. 38 Eating breakfast regularly supports postpartum weight loss.39 A combination of diet and exercise is most effective in supporting weight loss as well as improving maternal cardiovascular fitness.40 exercise during Pregnancy An active, physically fit woman experiencing a normal pregnancy can continue to exercise throughout pregnancy, adjusting the duration, intensity, and type of activity as the pregnancy progresses. Inactive women and those experiencing pregnancy complications should discuss physical activity options with their health care provider. With approval, inactive women can safely begin walking three to four times per week, gradually increasing from 25 to 40 minutes per session.41 Physical activity during pregnancy offers many benefits.42 Staying active can improve cardiovascular fitness, limit excessive weight gain, prevent or manage gestational diabetes and gestational hypertension, and reduce stress.43 Women who exercise during pregnancy report fewer discomforts throughout their preg- nancies. Regular exercise develops the strength and endurance a woman needs to carry the extra weight through pregnancy and to labor through an intense 450 Chapter 14 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  Figure 14-8 exercise guidelines during Pregnancy DO DON’T Do begin to exercise gradually. Don’t exercise vigorously after long periods of inactivity. Do exercise regularly (most, if not all, days of the week). Don’t exercise in hot, humid weather. Do warm up with 5 to 10 minutes of Don’t exercise when sick with fever. light activity. Don’t exercise while lying on your Do 30 minutes or more of moderate back after the 1st trimester of physical activity. pregnancy or stand motionless for prolonged periods. Do cool down with 5 to 10 minutes Tracy Frankel/Getty Images of slow activity and gentle stretching. Don’t exercise if you experience any pain, discomfort, or fatigue. Do drink water before, after, and during exercise. Don’t participate in activities that may harm the abdomen or involve Do eat enough to support the jerky, bouncy movements. needs of pregnancy plus exercise. Pregnant women can enjoy the benefits of exercise. Don’t scuba dive. Do rest adequately. delivery. It also maintains the habits that help a woman lose excess weight and get back into shape after the birth. A pregnant woman should participate in low-impact activities and avoid sports in which she might fall or be hit by other people or objects. For exam- ple, playing singles tennis with one person on each side of the net is safer than a fast-moving game of racquetball in which the two competitors can collide. Swimming and water aerobics are particularly beneficial because they allow the body to remain cool and move freely with the water’s support, thus reducing back pain. Figure 14-8 provides some guidelines for exercise during pregnancy. Several of the guidelines are aimed at preventing excessively high internal body temperature and dehydration, both of which can harm fetal development. To this end, pregnant women should also stay out of saunas, steam rooms, and hot tubs or hot whirlpool baths. ❯REVIEW IT Explain how both underweight and overweight can interfere with a healthy pregnancy and how weight gain and physical activity can support maternal health and infant growth. A healthy pregnancy depends on a sufficient weight gain. Women who begin their pregnancies at a healthy weight need to gain about 30 pounds, which covers the growth and development of the placenta, uterus, blood, breasts, and infant. By remaining active throughout pregnancy, a woman can develop the strength she needs to carry the extra weight and maintain habits that will help her lose weight after the birth. 14-4 nutrition during Pregnancy ❯ LEARN IT Summarize the nutrient needs of women during pregnancy. A woman’s body changes dramatically during pregnancy. Her uterus and its supporting muscles increase in size and strength; her blood volume increases by half to carry the additional nutrients and other materials; her joints become more f lexible in preparation for childbirth; her feet swell in response to high concentrations of the hormone estrogen, which promotes water retention and helps to ready the uterus for delivery; and her breasts enlarge in preparation for lactation. The hormones that mediate all these changes may influence her mood. She can best prepare to handle these changes given a nutritious diet, reg- ular physical activity, plenty of rest, and caring companions. This section high- lights the role of nutrition. Life Cycle nutrition: Pregnancy and Lactation 451 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  In general, the following guidelines will allow most women to enjoy a healthy pregnancy: Strive for good nutrition and health prior to pregnancy and get prenatal care during pregnancy. Gain a healthy amount of weight. Eat a balanced diet, safely prepared, and engage in physical activity regularly. Take prenatal vitamin and mineral supplements as prescribed. Refrain from cigarettes, alcohol, and drugs (including herbal remedies, unless prescribed by a physician). An adequate diet may also help a woman manage the challenges and possible depression that can arise after the infant arrives. Details follow. energy and nutrient needs during Pregnancy From conception to birth, all parts of the infant—bones, muscles, blood cells, skin, and all other tissues—are made from nutrients in the foods the mother eats (see Photo 14-3). For most women, nutrient needs during pregnancy and lactation are higher than at any other time (see Figure 14-9). Yet intakes do not consistently meet recom- Rachel Weill/Jupiter Images mendations for energy and key nutrients.44 To meet the high nutrient demands of pregnancy, a woman will need to make careful food choices, but her body will also help by maximizing absorption and minimizing losses. The Dietary Reference In- takes (DRI) table on the inside front cover provides separate listings for women during pregnancy and lactation, reflecting their heightened nutrient needs. PHoTo 14-3 A pregnant woman’s food energy The enhanced work of pregnancy raises the woman’s basal metabolic rate choices support both her health and her dramatically and demands extra energy. After the first trimester, energy needs of infant’s growth and development. pregnant women are greater than those of nonpregnant women—an additional 340 kcalories per day during the second trimester and an extra 450 kcalories per day during the third trimester. A woman can easily get these added kcalories with nutrient-dense selections from the five food groups. See Table 2-3 (p. 43) for Figure 14-9 Comparison of nutrient recommendations for nonpregnant, Pregnant, and Lactating Women For actual values, turn to the table on the inside front cover. For vitamins and minerals not shown here, the values do not change for pregnant and lactating women. Vitamins Minerals Percent Percent 0 50 100 150 200 250 0 50 100 150 200 250 Biotin Chromium Choline Copper The increased need for Folate Iodine iron in pregnancy cannot be met by diet or by Niacin Iron existing stores. Therefore, iron supplements are Pantothenic acid Magnesium recommended. Riboflavin Manganese Thiamin Molybdenum Vitamin A Potassium Vitamin B6 Selenium Vitamin B12 Zinc Vitamin C Vitamin E Key: Nonpregnant (set at 100% for a woman 24 years old) Pregnant Lactating 452 Chapter 14 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  Figure 14-10 Daily Food Choices for Pregnant and Lactating Women Food group amount SaMPLe Menu Fruits 2c Breakfast Dinner 1 whole-wheat English muffin Chicken cacciatore 2 tbs peanut butter 3 oz chicken Vegetables 2½–3 c 1 c low-fat vanilla yogurt ½ c stewed tomatoes ½ c fresh strawberries 1 c rice 1 c orange juice ½ c summer squash 1½ c salad (spinach, Grains 6–8 oz Midmorning snack mushrooms, carrots) ½ c cranberry juice 1 tbs salad dressing 1 oz pretzels 1 slice Italian bread Protein 5½–6½ oz Lunch 2 tsp soft margarine foods Sandwich (tuna salad on 1 c low-fat milk whole-wheat bread) ½ carrot (sticks) Milk 3c 1 c low-fat milk NOTE: The range of recommended amounts reflects the differences of the first trimester versus the second and third trimesters. This sample meal plan provides about 2500 kcalories (55% from carbohydrate, 20% from protein, and 25% from fat) and meets most of the vitamin and mineral needs of pregnant and lactating women. suggested dietary patterns for several kcalorie levels. A sample menu for pregnant and lactating women is presented in Figure 14-10. For a 2000-kcalorie daily intake, these added kcalories represent about 15 to 20 per- cent more food energy than before pregnancy. The increase in nutrient needs is often greater than this, so nutrient-dense foods should be chosen to supply the extra kcal- ories: foods such as whole-grain breads and cereals, legumes, dark green vegetables, citrus fruits, low-fat milk and milk products, and lean meats, fish, poultry, and eggs. Carbohydrate Ample carbohydrate (ideally, 175 grams or more per day and cer- tainly no less than 135 grams) is necessary to fuel the fetal brain. Sufficient car- bohydrate also ensures that the protein needed for growth will not be broken down and used to make glucose. Protein The protein RDA for pregnancy is an additional 25 grams per day higher than for nonpregnant women. Pregnant women can easily meet their protein needs by selecting meats, milk products, and protein-containing plant foods such as le- gumes, whole grains, nuts, and seeds. Because use of high-protein supplements dur- ing pregnancy may be harmful to the infant’s development, it is discouraged unless medically prescribed and carefully monitored to treat fetal growth problems.45 essential Fatty acids The high nutrient requirements of pregnancy leave little room in the diet for excess fat, but the essential long-chain polyunsaturated fatty acids are particularly important to the growth and development of the fetus.46 The brain is largely made of lipid material, and it depends heavily on the long- chain omega-3 and omega-6 fatty acids for its growth, function, and structure.47 (See Table 5-4 on p. 153 for a list of good food sources of the omega fatty acids.) nutrients for Blood Production and Cell growth New cells are laid down at a tre- mendous pace as the fetus grows and develops. At the same time, the mother’s red blood cell mass expands. All nutrients are important in these processes, but for folate, vitamin B12, iron, and zinc, the needs are especially great because of their key roles in the synthesis of DNA and new cells. The requirement for folate increases dramatically during pregnancy (from 400 micrograms to 600 micrograms daily). It is best to obtain sufficient folate from a combination of supplements, fortified foods, and a diet that includes fruits, juices, green vegetables, and whole grains. How To 10-3 on p. 317 describes how folate from each of these sources contributes to a day’s intake. The pregnant woman also has a slightly greater need for the B vitamin that ac- tivates the folate enzyme—vitamin B12. Generally, even modest amounts of meat, Life Cycle nutrition: Pregnancy and Lactation 453 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203  fish, eggs, or milk products together with body stores easily meet the need for vitamin B12. Vegans who exclude all foods of animal origin, however, need daily supplements of vitamin B12 or vitamin B12–fortified foods to prevent the neuro- logical complications of a deficiency. Pregnant women need iron to support their increased blood volume and to provide for placental and fetal needs.48 The developing fetus draws on mater- nal iron stores to create sufficient stores of its own to last through the first 4 to 6 months after birth. Ideally, a woman enters pregnancy with adequate iron stores and maintains sufficient iron nutrition throughout the pregnancy.49 The transfer of significant amounts of iron to the fetus is regulated by the placenta, which gives the iron needs of the fetus priority over those of the mother.50 Women with inadequate iron stores are left with too little iron to meet their own health needs. In addition, blood losses are inevitable at birth and can further drain the mother’s iron supply. During pregnancy, the body makes several adaptations to help meet the ex- ceptionally high need for iron. Menstruation, the major route of iron loss in women, ceases, and iron absorption improves thanks to an increase in transfer- rin, the body’s iron-absorbing and iron-carrying protein. Without sufficient in- take, though, iron stores quickly dwindle. Women with iron-deficiency anemia are likely to give birth to low-birthweight infants.51 Few women enter pregnancy with adequate iron stores, so a daily iron supple- ment is recommended early in pregnancy, if not before.52 To enhance iron ab- sorption, the supplement should be taken between meals or at bedtime and with liquids other than milk, coffee, or tea, which inhibit iron absorption. Drinking orange juice does not enhance iron absorption from supplements as it does from foods; vitamin C enhances iron absorption by converting iron from ferric to fer- rous, but supplemental iron is already in the ferrous form. Vitamin C is helpful, however, in preventing the premature rupture of amniotic membranes. > Die Ta ry guiDeL ine S F or a MeriC a nS 2 0 15 – 2 0 2 0 Women who are pregnant should take an iron supplement as recommended by an obste- trician or other health care provider. Zinc is required for DNA and RNA synthesis and thus for protein synthesis and cell development. Typical zinc intakes for pregnant women are lower than recom- mendations, but fortunately, zinc absorption increases when intakes are low. nutrients for Bone Development Vitamin D and the bone-building minerals cal- cium, phosphorus, magnesium, and fluoride are in great demand during preg- nancy. All are needed to produce healthy fetal bones and teeth.53 Vitamin D plays a central role in calcium absorption and utilization. Conse- quently, severe maternal vitamin D deficiency interferes with normal calcium me- tabolism, resulting in rickets in the infant and osteomalacia in the mother.54 Regular exposure to sunlight and consumption of vitamin D–fortified milk are usually suf- ficient to provide the recommended amount of vitamin D during pregnancy, which is the same as for nonpregnant women.55 Pregnant women who do not receive suf- ficient dietary vitamin D or enough exposure to sunlight may need a supplement. Calcium absorption and retention increases dramatically in pregnancy, helping the mother to meet the calcium needs of pregnancy. During the last trimester, as the fetal bones begin to calcify, up to 350 milligrams a day are transferred to the fetus. If the diet is inadequate in calcium, the mother’s bones give up their calcium to meet fe- tal needs and become less dense.56 Recommendations to ensure an adequate calcium intake during pregnancy help to conserve maternal bones while meeting fetal needs. Calcium intakes for pregnant women typically fall below recommendations. Because bones are still actively depositing minerals until about age 30, adequate calcium is especially important for young women. Pregnant women younger than age 25 who receive less than 600 milligrams of dietary calcium daily need to increase their intake of milk, cheese, yogurt, and other calcium-rich foods. The USDA Food Patterns suggest consuming 3 cups per day of fat-free or low-fat 454 Chapter 14 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated,