Chapter 4 Nutrition During Pregnancy

1. Chapter 4Nutrition During Pregnancy Nutrition Through the Life Cycle Judith E. Brown

2. Introduction • Topics covered include: • Status of pregnancy outcome • Reducing infant mortality and morbidity • Physiology of pregnancy • Embryonic & fetal growth and developmen • Pregnancy weight gain • Nutrition and course/outcome of pregnancy • Nutrient needs during pregnancy

3. Introduction • Topics covered include: • Exercise and Pregnancy • Food Safety issues during pregnancy • Common Health Problems during pregnancy

4. Time-related Terms Before, During, and After Pregnancy

5. The Status of Pregnancy Outcomes • Infant mortality: • Reflects general health status of a population • Decreases in mortality related to improvements in social circumstances, safe & nutritious food supply, & infectious disease control

6. Natality Statistics: Rates, Definitions, and Trends in the Rates in the United States

7. Differences by Race http://www.cdc.gov/nchs/data/databriefs/db09.htm

8. Chronology of Events Related to Declines in Infant Mortality in the United States

9. Low Birthweight, Preterm Delivery, and Infant Mortality • Low birth weight or preterm infants at high risk of dying in 1st year of life • 8.2% of births are LBW yet comprise 66% of infant deaths • 12.7% are born preterm yet account for high incidence of infant deaths

10. Reducing Infant Mortality and Morbidity • Improve birth weight of newborns • Desirable birth weight = 3500-4500 g (7 lb. 12 oz.-10 lb.) • Infants born with desirable wt are less likely to develop: • Heart and Lung diseases • Diabetes • Hypertension

11. Health Objectives for 2010 for the Nation Related to Pregnant Women and Infants • The Health Objectives for 2010 in relation to pregnant women and infants focus on • The reduction of low birth weight, • Preterm delivery • Infant mortality • A number of the objectives are related to nutrition

12. Health Objectives for 2010 for the Nation Related to Pregnant Women and Infants • Nutrition related objectives: • Reduce anemia in pregnant females • Reduce incidence of spina bifida • Increase abstinence form alcohol use and reduce the incidence of fetal alcohol syndrome • Increase appropriate weight gain during pregnancy

13. Physiology of Pregnancy • Key terms: • Gestational age • Assessed from date of conception • Average pregnancy is 38 weeks • Menstrual age • Assessed from onset of last menstrual period • Average pregnancy is 40 weeks

14. Maternal Physiology • Changes in maternal body composition & functions occur in specific sequence

15. Normal Physiological Changes during Pregnancy • Two phases of changes: • Maternal anabolic changes • Takes place in the 1st half of pregnancy • Maternal catabolic changes • Takes place in the 2nd half of pregnancy

16. Maternal Anabolic and Catabolic Phases of Pregnancy

17. Body Water Changes • Body water • Increases from ~7 L to 10 L • Results from increased blood and body tissues & extracellular volume & amniotic fluid • Edema • Swelling due to accumulation of extracelluar fluid

18. Key Placental Hormones and Examples of their Roles

19. Maternal Nutrient Metabolism • Changes can be seen in the first few weeks after conception. • Ensures that nutrients will be available to the fetus when needed.

20. Carbohydrate Metabolism • Glucose is preferred fuel for fetus • “Diabetogenic effect of pregnancy” results from maternal insulin resistance

21. Carbohydrate Metabolism • Early pregnancy: • High estrogen & progesterone stimulate insulin which increases glucose glycogen & fat • Late pregnancy: • Human chorionic somatotropin (hCS) & prolactin inhibit conversion of glucose to glycogen & fat

22. About 925 g of protein accumulate during pregnancy Protein & amino acids conserved during pregnancy No evidence the body stores protein early in pregnancy Needs must be met by mother’s intake of protein Protein Metabolism

23. Fat Metabolism • Fat stores • Accumulate in first half of pregnancy • Enhanced fat mobilization in last half • Blood lipid levels increase • Increased cholesterol is substrate for steroid hormone synthesis

24. Mineral Metabolism • Calcium • Increased bone turnover & reformation • Sodium • Accumulation in mother, placenta, & fetus • Restriction of sodium potentially harmful

25. The Placenta • Functions: • Hormone & enzyme production • Nutrient & gas exchange • Remove waste from fetus • Structure: • Double lining of cells separating maternal & fetal blood

26. Structure of the Placenta

27. The Placenta • Nutrient Transfer • Factors that affect the transfer: • Size and charge of molecules • Small molecules pass through most easily • Lipid solubility of particles • Concentration of nutrients in maternal and fetal blood

28. The Placenta • Nutrient Transfer • The fetus is not a parasite • Nutrients first used for maternal needs, then for placenta & last for fetal needed • The fetus is harmed more than the mother by poor maternal nutrition

29. Embryonic and Fetal Growth and Development • Growth and Development • Is at the highest level during the 9 months of gestation • If rate gain continued at this level, at 1 year of age the infant would be 160 lbs. • Table 4.12 provides an overview of embryonic and fetal development during pregnancy

30. Critical Periods of Growth and Development • Differentiation • Cellular acquisition of one or more characteristics or functions different from that of the original cell • Critical Periods • Preprogrammed time periods during embryonic & fetal development when specific cells, organs & tissues are formed & integrated or functional levels established

31. Critical Periods of Growth and Development • Four periods of growth & development 1) Hyperplasia( cell multiplication) 2) Hyperplasia & hypertrophy 3) Hypertrophy( cell growth) 4) Maturation (stabilization of cell number & size)

32. Fetal Body Composition

33. Variation in Fetal Growth • Variations linked to: • Energy, nutrient, & oxygen availability • Genetically programmed growth & development • Insulin-like growth factor (IGF-1) is main fetal growth stimulator

34. Newborn Weight Classifications • Terms to describe newborn size • SGA (small for gestational age) • dSGA (disproportionately small for gestational age) • pSGA (proportionately small for gestational age) • LGA (large for gestational age) • Ponderal Index (similar to BMI) • Calulated by wt in g divided by cube of lt times 100 • PI for normal wt ~23-25

35. Nutrition, Miscarriages and Preterm Delivery • Miscarriages • Thought to be caused by genetic, uterine, or hormonal abnormalities • Preterm Delivery • Infants born preterm are at risk for death, neurological problems, congenital malformations, & chronic health problems

36. Fetal-Origins Hypothesis of Later Disease Risk • Theory that exposures to adverse nutritional & other conditions during critical or sensitive periods of growth & development can permanently affect body structures & functions • Changes may predispose individuals to CVD, type 2 diabetes, hypertension, & other disorders in later life

37. The Fetal-Origins Hypothesis • Mechanisms underlying the fetal origins hypothesis • Influenced by genes • Also influenced by environmental exposure (in utero) • AKA developmental plasticity • Concept that the development can be modified by particular environmental conditions experienced by a fetus or infant

38. The Fetal-Origins Hypothesis • Environmental Exposures • Modify development • Epigenetic mechanisms • Epigenetics (epi=over, above) • Biological mechanisms that change gene function without changing the structure of DNA. Epigenetic mechanisms are affected by environmental factors.

39. The Fetal-Origins Hypothesis • Nutrition programming • Fetal exposure to certain levels of energy & nutrients modify function of genes in ways that affect metabolism & development of diseases in later life • Limitations of the fetal-origins hypothesis • Unanswered questions • What levels are related to changes? • What exposures?

40. Pregnancy Weight Gain • Weight gain during pregnancy is related to the weight and health status of the newborn infant • Recommendations for weight gain during pregnancy is found in Table 4.17 • Recommendations for weight gain are influenced by the pre-pregnancy status of the mother

41. Pregnancy Weight Gain Recommendations

42. ~2-5 pounds in first trimester Gradual & consistent gains thereafter Rate of Pregnancy Weight Gain

43. The Institute of Medicine’s Prenatal Weight-gain Graph

44. Composition of Weight Gain • The fetus is only about 1/3 of the total weight gain • The balance of the weight gain is related to body fat changes, placenta, amniotic fluid, increase of extracellular fluids, and blood supply of the mother

45. Postpartum Weight Retention • Much concern over pregnancy weight gain and long-term obesity • ~15 pounds lost at delivery • Wt loss difficult in women who gained >45 pounds or with low activity levels • Women with recommended wt gain in pregnancy are ~2 pounds heavier at 1 yr postpartum • Lactating women lose slightly more

46. Nutrition and the Course and Outcome of Pregnancy • Famine and pregnancy outcome • The Dutch Hungerwinter, 1943-1944 • Decline in pregnancy rates • Lower birth weights • The siege of Leningrad, 1942 • Increase in infertility & low birth weights • Infant death rates increased • Food shortages in Japan • Similar to the outcomes found in Holland and Leningrad above

47. Nutrition and the Course and Outcome of Pregnancy • Contemporary prenatal nutrition research results • “Good nutritional status maintained before and throughout pregnancy decreases the risk of birth defects, suboptimal fetal growth and development, and chronic health problems later in life.”

48. Nutrient Needs During Pregnancy • Nutrient needs vary during the course of the pregnancy • Overall, nutrient needs can be met with well balanced, adequate and healthful diets consisting of basic foods

49. Nutrient Needs During Pregnancy • Energy requirements in pregnancy • ~300 additional cal/d • +340/d in 2nd trimester +452/d in 3rd trimester • Assessment of caloric intake • Most easily assessed by pregnancy weight gain • As long as there is no noticeable edema

50. Carbohydrates, Artificial Sweeteners and Alcohol • Carbohydrate intake (50-65%) • Basic foods such as • vegetables, fruits, and whole grains with fibers = best choice • Artificial sweeteners • No scientific evidence of harm • Alcohol ingestion • Strongly advised to avoid during pregnancy