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Title: Physiological%20adaptations%20to%20pregnancy


1
Lecture 2 - 2006
  • 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.
6
TABLE 8-4. Ventilatory Function in Pregnant Women Compared with the Postpartum Period TABLE 8-4. Ventilatory Function in Pregnant Women Compared with the Postpartum Period TABLE 8-4. Ventilatory Function in Pregnant Women Compared with the Postpartum Period TABLE 8-4. Ventilatory Function in Pregnant Women Compared with the Postpartum Period TABLE 8-4. Ventilatory Function in Pregnant Women Compared with the Postpartum Period
  During Pregnancy During Pregnancy During Pregnancy
Factor 10 Weeks 24 Weeks 36 Weeks Postpartum 6-10 Weeks
Respiratory rate 15-16 16 16-17 16-17
Tidal volume (mL) 600-650 650 700 550a
Minute ventilation (L) 10.5 7.5a
Vital capacity (L) 3.8 3.9 4.1 3.8
Inspiratory capacity (L) 2.6 2.7 2.9 2.5
Expiratory reserve volume (L) 1.2 1.2 1.2 1.3
Residual volume (L) 1.2 1.1 1.0 1.2a
a Significant increase or decrease compared with pregnant women. a Significant increase or decrease compared with pregnant women. a Significant increase or decrease compared with pregnant women. a Significant increase or decrease compared with pregnant women. a Significant increase or decrease compared with pregnant 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 200071
(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
7. Alterations in maternal physiology facilitate
transfer of nutrients to the fetus.
15
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

16
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

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19
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.

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21
Mean hemoglobin concentrations (    ) and 5th
and 95th (    ) percentiles for healthy
pregnant women taking iron supplements
22
Maternal Nutrient Levels
23
Nitrogen Balance (g/day)
24
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

25
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

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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

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29
Mechanisms of Nutrient Transfer Across the
Placenta
30
Maternal to Infant Nutrient Transportation Across
The Placenta
31
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
Other Placental Functions
35
Psychology of Pregnancy
  • Psychosocial tasks
  • Rubin
  • Leadermans tasks
  • Fathers
  • Cultural awareness

36
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.

37
Maternal Focus
Trimester
1 Im pregnant!
2 Theres a BABY..
3 Im going to be a MOM
38
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

39
Psychosocial adjustment during pregnancy the
experience of mature gravidas (Stark, JOGNN, 1997)
  • N64 older gravidas (gt 35), 46 younger gravidas
    (lt 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

40
Adolescents PSYCHOSOCIAL FACTORS THAT INFLUENCE
TRANSITION TO MOTHERHOOD (kaiser, 2004)
  • Gaining acceptance of the pregnancy in the family
    system
  • Awareness of the need to develop a sense of
    responsibility
  • Planning for a future that includes the baby
  • Viewing self as a mother

41
Laboring for Relevance Expectant and New
Fatherhood (Jordan, Nursing Research, 1990)
  • N56 expectant fathers followed prospectively
  • Fathers reported
  • 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

42
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

43
Jordons Developmental Tasks of Fatherhood
  • Accepting the pregnancy
  • Identifying the role of father
  • Reordering relationships
  • Establishing relationship with his child
  • Preparing for the birth experience

44
What about Dad? Psychosocial and mental health
issues for new fathers. (Condon, 2006. The
Australian First Time Fathers Study)
  • Tasks
  • Developing an attachment to the fetus
  • Adjusting to the dyad becoming a triad
  • Conceptualizing the self as father
  • What type of father?

45
Energy Requirements in Pregnancy
  • Energy costs of pregnancy
  • increased maternal metabolic rate
  • fetal tissues
  • increase in maternal tissues

46
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

47
DRI for Energy - New
48
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49
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

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DRI for Energy in Pregnancy - 2002
57
BEE Basal Energy Expenditure
  • Increases due to metabolic contribution of uterus
    and fetus and increased work of heart and lungs.
  • Variable for individuals

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59
Growth of Maternal and Fetal Tissues
  • Still based on work of Hytten
  • Based on IOM weight gain recommendations

60
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62
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.

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64
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?

65
Evidence of energy sparing in Gambian women
during pregnancy a longitudinal study using
whole-body calorimetry (AJCN, 1993)
  • N58, 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

66
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

67
Poppitt et al., cont.
  • BMR fell in early pregnancy
  • Values per kg lbm remained below baseline for
    duration of pregnancy
  • Individual variation was high

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69
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

70
  • Prentice and Goldberg. Energy Adaptations in
    human pregnancy limits and long-term
    consequences. Am J Clin Nutr.
    200071(supple)1226S-32S.

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72
Longitudinal assessment of energy balance in
well-nourished, pregnant women (Koop-Hoolihan et
al, AJCN, 1999)
  • N16, SF area
  • 10 became pregnant
  • BMI range was 19-26
  • Mean weight gain at 36 weeks was 11.6 4
  • Mean birth weight was 3.6

73
Koop-Hoolihan, cont
  • Protocol 5 times before pregnancy, 3 times
    during, once 4-6 weeks postpartum
  • RMR (resting metabolic rate/metabolic cart)
  • DIT (diet induced thermogenesis/metabolic cart)
  • TEE (total energy expenditure/doubly labeled
    water)
  • AEE (activity energy expenditure/difference
    between TEE and RMR)
  • EI (energy intake/3 day food records)
  • Body composition - densitometry, tbw, bmc with
    absorptiometry

74
Koop-Hoolihan, cont
  • Women with the largest cumulative increase in RMR
    deposited the least fat mass (this was the only
    prepregnant factor that predicted fat mass gain)
  • In all indices there was large individual
    variation
  • Average total energy cost of pregnancy was
    similar to work of Hytten and Leitch (1971)
  • Food intake records indicated 9 increase in
    kcals with pregnancy, but highly variable

75
Energy in Pregnancy (Roy Pitkin, AJCN, 1999)
  • Koop-Hoolihan study design was Impeccable.
  • Women meet increase energy demands of pregnancy
    in a variety of ways - increased intakes,
    decreased activity or DIT, limited fat storage.
  • RDA?

76
Energy in Pregnancy (Roy Pitkin, AJCN, 1999)
  • A prudent course seems to be to permit
    considerable latitude in energy intake
    recommendations on the basis of individual
    preferences and to monitor weight gain carefully,
    making adjustments in energy intake only in
    response to the normal pattern of gain.

77
Maternal Obesity
  • Rates of obesity are increasing world-wide
  • Obesity before pregnancy is associated with risk
    of several adverse outcomes

78
Prepregnancy weight and the risk of adverse
pregnancy outcomes (Cnattingius et al, NEJM, 1998)
  • N167,750 in Sweden, Norway, Finland, or Iceland
    who gave birth to singleton babies in 1992 and
    1993.
  • Outcome late fetal death
  • Adjusted for maternal age, parity, education,
    smoking, height and living with father

79
Prepregnancy weight and the risk of adverse
pregnancy outcomes (Cnattingius et al, NEJM, 1998)
80
Prepregnancy weight and the risk of adverse
pregnancy outcomes (Cnattingius et al, NEJM, 1998)
81
Cnattingius et al, Discussion
  • Even lean women were probably well nourished in
    this cohort. Results in other countries may be
    different.
  • Maternal overweight may be major factor in SES
    differences in perinatal morbidity and mortality
  • Impetus toward developing strategies to reverse
    trends toward increasing body weight

82
Perinatal Outcomes of Obese Women A Review of
the Literature (Morin, JOGNN, 1998)
Nutrition and Pregnancy Outcome Henriksen,
Nutrition Reviews, 2006
  • Extensive Review of Medine and CINAHL
  • Definitions of obesity vary, but IOM says obesity
    BMI gt 29

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84
Diagnosis
  • Menses tend to be irregular and pelvic exams and
    ultrasound exams may be difficult
  • AFP values may be lower than norms due to
    increased plasma volume
  • Blood pressure monitoring may be difficult

85
Antepartum Outcomes
  • Higher rates of NTD even with folic acid
    supplementation (RR 3.0 in one study)
  • Increased risk for both chronic and pregnancy
    induced hypertension
  • Increased risk for severe preeclampsia (BMI lt
    32.3, risk was 3.5 times that of controls)
  • Increased risk for both GDM, IDD and NIDD.
  • Increased twining
  • Increased UTI

86
Labor and Birth Outcomes
  • Increased incidence of both primary (31 vs 8.6)
    and secondary cesarean births - often associated
    with fetal macrosomia and/or failed induction.
  • Operative times are longer
  • Increased incidence of blood loss during surgery
  • ? Differences in responses to anesthesia (greater
    spread/higher levels)

87
Postpartum Outcomes
  • Increased risk for wound and endometrial
    infection
  • Increased prevalence of urinary incontinence

88
Infant Outcomes
  • Large infants - effect is independent of maternal
    diabetes
  • Increased infant mortality - RR for infants born
    to obese women was 4.0 compared to women with BMI
    lt 20

89
Swedish population-based study (n805,275)
90
Swedish population-based study (n805,275)
  • Morbid obesity (BMIgt40) compared to normal
    weight
  • 5 fold risk of preeclampsia
  • 3 fold risk of still birth after 28 weeks
  • 4 fold risk of LGA
  • BMI gt35, lt40, associations remain, but not as
    strong

91
Cost
  • Costs were 3.2 times higher for women with BMI gt
    35
  • Longer hospitalizations

92
Maternal Obesity and Pregnancy Outcomes Castro
Alvina, Curr Opin obstet Gynecol, 2002
Increased Risk in Obese Women
Pre-eclampsia 2 to 4 times as high
Diabetes 3 times as high
Postpartum hemorrhage 70 increase
Infant shoulder dystocia 2 times as high
Thromboembolic disease
Respiratory complications
93
IOM Recommendations
  • Institute of Medicine. Nutrition during
    pregnancy, weight gain and nutrient supplements.
    Report of the Subcommittee on Nutritional Status
    and Weight Gain during Pregnancy, Subcommittee on
    Dietary Intake and Nutrient Supplements during
    Pregnancy, Committee on Nutritional Status during
    Pregnancy and Lactation, Food and Nutrition
    Board. Washington, DC National Academy Press,
    1990

94
Recommended total weight gain in pregnant women
by prepregnancy BMI (in kg/m2) Weight-for-height
category Recommended total gain (kg) Low (BMI
lt19.8) 12.518 Normal (BMI 19.826.0) 11.516
High (BMI gt26.029.0)2 711.5 Adolescents and
black women should strive for gains at the upper
end of the recommended range. Short women (lt157
cm) should strive for gains at the lower end of
the range. The recommended target weight gain for
obese women (BMI gt29.0) is 6.0.
95
Cogswell M, Serdula M, Hungerford D, Yip R.
Gestational weight gain among average-weight and
overweight womenwhat is excessive? Am J Obstet
Gynecol 199517270512
96
Incidence of adverse outcomes for 6690
pregnancies in San Francisco
Parker J, Abrams B. Prenatal weight gain advice
an examination of the recent prenatal weight gain
recommendations of the Institute of Medicine.
Obstet Gynecol 1992796649
97
Percentage of US women with normal prepregnancy
weights who retained gt9 kg 1024 mo postpartum
relative to prepregnancy weight
(Parker J, Abrams B. Differences in postpartum
weight retention between black and white mothers.
Obstet Gynecol 19938176874)
98
Rates of Weight Gain T2 and T3
  • Underweight women 0.5 kg per week
  • Normal weight women 0.4 kg per week
  • Overweight women 0.3 kg per week

99
Postpartum Weight
  • IOM (1990) concluded that childbearing is
    associated with average weight gain of 1kg.
  • There is a large variation in differences between
    prepregnant weight and weight at 6 to 12 months
    postpartum (SD of 4.8 kg)
  • Analysis is confused by the tendency to gain
    weight with aging
  • Years between 25 and 34 are times when American
    women are most vulnerable to major weight gain

100
Postpartum Weight
  • Proportions of black women who have higher
    postpartum weights is higher in almost all
    studies.
  • Smoking is consistently related to less
    postpartum weight gain.

101
Predictors of weight gain at 6 and 18 months
after childbirth a pilot study (Walker, JOGNN,
1996)
  • N88 at 6 months, 75 at 18 months
  • Out of about 300 who were sent a mailed
    questionnaire 6 and 18 months postpartum
  • Predominantly white mothers in the Midwestern US

102
Predictors of weight gain at 6 and 18 months
after childbirth a pilot study (Walker, JOGNN,
1996)
  • Battery of tests including
  • Health promoting lifestyle profile (48 items on
    exercise, nutrition, support self-actualization)
  • Categories of activity level
  • Weight locus of control scale (internal or
    external)
  • Self reported weight and height, method of
    delivery, method of infant feeding

103
Predictors of weight gain at 6 and 18 months
after childbirth a pilot study (Walker, JOGNN,
1996)
104
Walker, Results
  • At both 6 and 18 months, women who exceeded IOM
    wt. Gain recommendations had significantly higher
    pp weight increases.

105
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106
Sociocultural and behavioral influences on weight
gain during pregnancy
  • Hicky, CA. Am J Clin Nutr. 200071(supple)1364S
    -70S.

107
Percent of Women Gaining lt 7.3 kg
108
Characteristics of Women Associated with
Inadequate Weight Gain
  • Lower education levels
  • Unmarried
  • Aged gt 30 years
  • Smoking
  • Multiple parity

109
  • Possibly psycho-social stress and pregnancy
    intendedness (effects seem to differ by culture)
  • Low income women had twice the risk in NNS.
  • Migrant workers have higher risk in WIC
    populations

110
1997 Review of Recommendations
  • Maternal Weight Gain A Report of an Expert Work
    Group. Suitor, CW. 1997. NCEMCH.

111
Recent Findings
  • Maternal water gain, which probably represents
    lean tissue, is a predictor of birthweight, fat
    gain is not predictive.
  • Effect size of energy intake on weight gain is
    modest.
  • When maternal weight gain is within IOM range,
    incidence of SGA LBW is reduced

112
Recent Findings, cont.
  • Increasing prevalence of obesity in population
    calls for reexamination of effects of pregnancy
    weight gain retention
  • Increased parity is associated with increased
    weight gain in adulthood.
  • Post delivery, African American women have
    greater weight retention than white women with
    the same pregnancy weight gain.

113
Recommendations for Practice
  • Promote use of IOM recommendations for rate of
    weight gain as well as total weight gain.
  • Promote strategies for weight gain within
    recommended ranges.
  • Promote healthy eating

114
  • Until more is known, two groups of special
    concern, Adolescents and African American women
    should be advised to stay within IOM ranges
    without either restricting weight gain or
    encouraging weight gain at the upper end of the
    range.

115
Multiple Births
  • Optimal range of birthweight
  • Twins 2500-2800 g at 36-37 weeks
  • Triplets 1900-2000 g at 34-36 weeks
  • Maternal weight gain of 16-20.5 kg with .75 kg
    per week during second half of pregnancy is
    associated with optimal twin birthweights (IOM).
  • Weight gain of lt 0.85 pounds per week before 24
    weeks associated with IUGR and morbidity.

116
Carmichael- what are women actually doing? (AJPH,
1998)
  • Cohort 7002 singleton deliveries with good
    outcomes at UCSF between 1980-1990
  • Good outcomes vaginal delivery, term (gt37
    weeks), live, AGA, no maternal diabetes or
    hypertension

117
Carmichael Results
118
Carmichael Discussion
  • More than half the women fell outside of IOM
    ranges
  • Higher gains may be associated with higher
    postpartum weight retention
  • Monitoring of weight gain is not highly sensitive
    when used in isolation
  • Many questions remain about the utility of
    monitoring weight gain, standards, and counseling.

119
Trends in weight gain during pregnancy A
population study across 16 years in North
Carolina Helms E et al., American Journal of
Obstetrics and Gynecology (2006) 194, e32e34
  • 1,463,936 registered North Carolina births from
    1988 to 2003
  • The percentage of pregnant women achieving
    recommended weight gain decreased significantly
    (down 6.3) between 1988 and 2003.

120
CDC Pregnancy Nutrition Surveillance
121
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