Lecture 2 - 2002

1. Lecture 2 - 2002 • Physiology • Psychology • Energy • Weight Gain

2. Physiology of Pregnancy

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

4. 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

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

6. There may be more than one adjustment for each nutrient. • Maternal behavioral changes augment physiologic adjustments • When adjustment limits are exceeded, fetal growth and development are impaired. • The first half of pregnancy is a time of preparation for the demands of rapid fetal growth in the second half

7. 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.

8. Hormonal Adjustments • 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

9. Late Gestation • Anti-insulinogenic and lipolytic effects of Human chorionic somatomammotropin, prolactin, cortisol, glucagon) • Glucose intolerance, insulin resistance, decreased hepatic glycogen, mobilization of adipose tissue

10. 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.

11. Maternal Nutrient Levels

12. Nitrogen Balance (g/day)

14. Nutrient Transportation Across The Placenta

15. Factors Affecting Placental Transfer • Diffusion distance - diabetes and infection • cause edema of the villi • Maternal-placental blood flow • Blood saturation with gases and nutrients • Maternal-placental metabolism of the substance

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

17. 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 ears. • Binding-in to her unknown baby. • Learning to give of herself.

18. 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

19. 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

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

21. 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

22. 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

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

24. 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

25. DRI for Energy - New

34. DRI for Energy in Pregnancy - 2002

35. BEE: Basal Energy Expenditure • Increases due to metabolic contribution of uterus and fetus and increased work of heart and lungs. • Variable for individuals

37. Growth of Maternal and Fetal Tissues • Still based on work of Hytten • Based on IOM weight gain recommendations

40. Longitudinal Data from DLW Database • Median TEE (total energy expenditure) change from non-pregnant was 8 kcal/gestational week. • TEE changes little in first trimester.

42. Variations in Energy Requirements • Body size - especially lbm • Activity: • most women decrease activity in last months of pregnancy if they can • increased energy cost of moving heavier body • BMR • rises in well nourished women (27%) • rises less or not at all in women who are not well nourished • -Diet Induced Thermogenesis?

43. Evidence of energy sparing in Gambian women during pregnancy: a longitudinal study using whole-body calorimetry (AJCN, 1993) • N=58, initially recruited, ages 18-40 • 25 became pregnant • 21 participated in study protocols • 9 completed BMR and 24 hour energy expenditure • 12 completed BMR • Adjusted for seasonality, weight loss expected during wet season

44. Poppitt et al., cont. • Mean maternal prepregnancy weight was 52 kg • Mean prepregnancy BMI was 21.2 + 2 • Mean birthweight was 3.0 + 0.1 • Mean gestational length was 39.4 • Mean weight gain was 6.8 kg • Mean fat gain was 2.0 kg at 36 weeks

45. Poppitt et al., cont. • BMR fell in early pregnancy • Values per kg lbm remained below baseline for duration of pregnancy • Individual variation was high

47. Poppitt et al., cont. • Energy sparing mechanisms may act via a suppression of metabolism in women on habitually low intakes. • This maintains positive balance in the mother and protects the fetus from growth retardation

48. Prentice and Goldberg. Energy Adaptations in human pregnancy: limits and long-term consequences. Am J Clin Nutr. 2000;71(supple):1226S-32S.

50. Five Country Study