Lecture 2 - 2005

1. Lecture 2 - 2005 • Physiological adaptations to pregnancy • Psychology • Energy • Weight Gain

2. Physiology of Pregnancy

3. Systematic Adjustments to Pregnancy • Cardiovascular • Respiratory • Urinary

4. Cardiac output during three stages of gestation, labor, and immediately postpartum compared with values of nonpregnant women. All values were determined with women in the lateral recumbent position.

5. Change in cardiac outline that occurs in pregnancy. The light lines represent the relations between the heart and thorax in the nonpregnant woman, and the heavy lines represent the conditions existing in pregnancy. These findings are based on x-ray findings in 33 women.

7. Mean glomerular filtration rate in healthy women over a short period with infused inulin (solid line), simultaneously as creatinine clearance during the inulin infusion (broken line), and over 24 hours as endogenous creatinine clearance (dotted line).

8. King J. Physiology of pregnancy and nutrient metabolism. Am J Clin Nutr 2000;71 (suppl):1218S-25S

9. Adjustments in Nutrient Metabolism • Goals • support changes in anatomy and physiology of mother • support fetal growth and development • maintain maternal homeostasis • prepare for lactation • Adjustments are complex and evolve throughout pregnancy

10. General Concepts 1. Alterations include: • increased intestinal absorption • reduced excretion by kidney or GI tract 2. Alterations are driven by: • hormonal changes • fetal demands • maternal nutrient supply

11. 3. There may be more than one adjustment for each nutrient. 4. Maternal behavioral changes augment physiologic adjustments 5. When adjustment limits are exceeded, fetal growth and development are impaired.

12. Birth weight of 11 children born to a poor woman in Montreal; 8 children were born before receiving nutritional counseling and food supplements from the Montreal Diet Dispensary and 3 children were born afterward.

13. 6. The first half of pregnancy is a time of preparation for the demands of rapid fetal growth in the second half

14. Hormonal Adjustments • Changes in over 30 different hormones have been detected in pregnancy • Estrogens: increase significantly in pregnancy, influence carbohydrate, lipid, and bone metabolism • Progesterone: relaxes smooth muscle and causes atony of GI and urinary tract • Human Placental Lactogen (hPL): stimulates maternal metabolism, increases insulin resistance, aids glucose transport across placenta, stimulates breast development

15. Late gestation is characterized by: • Anti-insulinogenic and lipolytic effects of Human chorionic somatomammotropin, prolactin, cortisol, glucagon) Which Results in: • Glucose intolerance, insulin resistance, decreased hepatic glycogen, mobilization of adipose tissue

17. Mean (±SEM) plasma lipid concentrations (mg/dL) throughout gestation (n = 42) and during the luteal (I) and follicular (II) phases postpartum (p.p.; n = 23). The dashed lines represent the mean values of the control group (n = 24). (FC = free cholesterol; PL = phospholipids; TC = total cholesterol; TG = triglycerides.)(

18. Maternal Nutrient Levels • Increased triglycerides • Increased cholesterol • Decreased plasma amino acids & albumin • Plasma volume increases 40% (range 30-50%) • nutrient concentration declines due to increased volume, but total amount of vitamins and minerals in circulation actually increases.

20. Mean hemoglobin concentrations (  —  ) and 5th and 95th (  —  ) percentiles for healthy pregnant women taking iron supplements

21. Maternal Nutrient Levels

22. Nitrogen Balance (g/day)

23. Alterations in maternal physiology facilitate transfer of nutrients to the fetus.

25. The Placenta • Early gestation (10-12 weeks) is the period of placentiation • Fetus is nourished by secretions of uterine endometrial glands in early gestation • Placenta is a metabolically active tissue • Responsible for exchange of nutrients, gases & metabolic waste products between maternal and fetal circulation • Glucose is predominant energy source for both placenta and fetus

26. Placental Architecture • Maternal and fetal blood do not mix: “placental barrier” • Fetal blood flows through capillary networks within highly branched terminal chorionic villi • Maternal blood flows through intervillous space • Uterine arteriols bring blood in • Uterine venules drain blood

27. Placental Capacity Increases During Gestation • Expression of transporters increases • The “brush border” microvilli develop to: • increase surface area • impede maternal blood flow • Flow through the placenta at term is 500 ml/minute

28. Mechanisms of Nutrient Transfer Across the Placenta

29. Maternal to Infant Nutrient Transportation Across The Placenta

30. Fetal to Maternal Transport • Carbon dioxide • Water & urea • Hormones

32. Factors Affecting Placental Transfer • Placental size • Diffusion distance – • diabetes and infection cause edema of the villi • distance decreases as pregnancy progresses and fetal needs increase • Maternal-placental blood flow • Blood saturation with gases and nutrients

33. Factors Affecting Placental Transfer (cont) • Maternal-placental metabolism of the substance • Disorders in expression or activity of nutrient transporters • Maternal use of tobacco, cocaine, alcohol

34. Psychology of Pregnancy • Psychosocial tasks • Rubin • Leaderman’s tasks • Fathers • Cultural awareness

35. Developmental Tasks of Pregnancy (Rubin, 1984) • Seeking safe passage for herself and her child through pregnancy, labor, and delivery. • Ensuring the acceptance by significant persons in her family of the child she bears. • Binding-in to her unknown baby. • Learning to give of herself.

36. Lederman, RP. Psychosocial Adaptation in Pregnancy, 2nd Ed. 1996 • Developmental Tasks of Pregnancy • acceptance of pregnancy • identification with motherhood role • relationship to the mother • relationship to the husband/partner • preparation for labor • processing fear of loss of control & loss of self esteem in labor

37. Psychosocial adjustment during pregnancy: the experience of mature gravidas(Stark, JOGNN, 1997) • N=64 older gravidas (> 35), 46 younger gravidas (< 32) in third trimester • Lederman prenatal self evaluation questionnaire - examines conflicts for 7 steps • In general conflicts about maternal role were similar in both groups • Older gravidas had less concern about fear of helplessness and loss of control in labor - regardless of parity

38. Developmental Tasks of Fatherhood • Accepting the pregnancy • Identifying the role of father • Reordering relationships • Establishing relationship with his child • Preparing for the birth experience

39. Laboring for Relevance: Expectant and New Fatherhood(Jordan, Nursing Research, 1990) • N=56 expectant fathers followed prospectively • “Tasks” • grappling with the reality of the pregnancy and child • struggling for recognition as a parent from mother, coworkers, friends, family baby and society • plugging away at the role-making of involved fatherhood

40. Jordan, cont. • Identified concerns: • Men not recognized as parents but as helpmates and breadwinners • Men felt excluded from childbearing experience by mates, health care providers, and society • Fathers felt that they had no role models for active and involved parenthood

41. Energy Requirements in Pregnancy • Energy costs of pregnancy: • increased maternal metabolic rate • fetal tissues • increase in maternal tissues

42. RDA for Energy in Pregnancy - Old • Energy cost of pregnancy = 80,000 kcal (Hytten and Leitch, 1971) • maternal gain of 12.5 kg • infant weight of 3.3 kg • 80,000/250 days (days after the first month) • Additional 300 kcal per day recommended in second and third trimester • total of 2,500 for reference woman

43. DRI for Energy - New

45. Estimated Energy Requirement • Average dietary energy intake that is predicted to maintain energy balance in a healthy adult of a defined age, gender, weight, height, level of physical activity consistent with good health. • In children, pregnant and lactating women the EER is taken to include the needs associated with deposition of tissues or secretion of milk