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MATERNAL RESPONSE TO PREGNANCY, PARTURITION AND NEONTATAL TRANSITION TO EXTRA-UTERINE LIFE

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Title: MATERNAL RESPONSE TO PREGNANCY, PARTURITION AND NEONTATAL TRANSITION TO EXTRA-UTERINE LIFE


1
MATERNAL RESPONSE TO PREGNANCY, PARTURITION AND
NEONTATAL TRANSITION TO EXTRA-UTERINE LIFE
  • ANSC 631
  • BAZER

2
MATERNAL RESPONSE TO PREGNANCY GENERAL
  • TIRED
  • SLEEPY
  • CARDIOVASCULAR ISSUES
  • APPETITE
  • MAMMARY DEVELOPMENT
  • CHANGE IN LIBIDO

3
NAUSEAU AND VOMITING
  • 4 to 6 weeks to 14-16 weeks of pregnancy
  • Hyperemesis gravidarum severe nausea, vomiting,
    weight loss, and sometimes electrolyte
    disturbance, may require hospitalization for
    intravenous fluid and nutrition.
  • Why
  • Ho adding spices to food inhibits growth of
    microorganisms and protects from diseases
  • expelling or avoiding foods during early months
    of pregnancy protects mother and embryo from
    foodborne illnesses and toxins, especially when
    the fetal development is most sensitive to
    disruption.

4
  American Scientist 89 (2)142 Protecting Ourselves from Food Spices and morning sickness may shield us from toxins and microorganisms in the diet. Paul W. Sherman, Samuel M. Flaxman SPECULATION Progesterone is analgesic with LD50 that may cause nausea by acting on nervous system like an anesthetic Changes in gut immune system response to food allergens, e.g., like some people respond to peanuts or shell fish


5
REVIEW OF DIGESTION
  • STOMACH
  • HCl, PEPSIN, RENIN AND GASTRIC LIPASE START
    PROCESS
  • SMALL INTESTINE
  • ENZYMES TRYPSIN, CHYMOTRIPSIN, ETC DIGEST
    PROTEINS
  • PROTEIN SOLUBILITY AND DIGESTIBILITY
  • AMINO ACIDS ABSORBED
  • CHYLE TO LACTEALS (LYMPH VESSELS) FOR
    SURVEILLANCE
  • LARGE INTESTINE
  • ABSORPS WATER AND SALTS

6
                       Maternal nutrition and
fetal development. J Nutr. 2004 1342169-2172 Wu
G, Bazer FW, Cudd TA, Meininger CJ, Spencer
TE. Nutrition intrauterine environmental factor
altering expression of fetal genome with lifelong
consequences ("fetal programming) and "fetal
origins of adult disease." 1) change structure,
physiology, and metabolism of offspring
predisposing individuals to metabolic, endocrine,
and cardiovascular diseases as adults 2)
maternal undernutrition and overnutrition reduce
placental-fetal blood flows and stunt fetal
growth. 3) impaired placental NO
(vasodilator/angiogenesis) and polyamines (DNA
and protein synthesis) result in intrauterine
growth retardation 4) nutritional status alters
epigenetic state through DNA methylation and
histone modifications of fetal genome thereby
impacting fetal programming and genomic
imprinting.

7
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8
MATERNAL CARDIOVASCULAR SYSTEM
  • 10-15 decrease in systemic arterial blood
    pressure
  • Decreased vascular tone systemic vascular
    resistance mean arterial pressure
  • cardiac output
  • PGE2, NO, PGI2 and decrease in alpha adrenergic
    receptor leads to vasodilation and decrease in
    mean arterial pressure

9
MATERNAL CARDIOVASCULAR SYSTEM
  • 25 to 60 increase in cardiac output
  • Increase mostly after mid-gestation
  • Cardiac output heart rate X stroke volume
  • Heart rate increase by 20 to 30
  • Stroke volume increase by 30-35
  • Increases in
  • Left Ventricle Mass
  • Left Atrial Size
  • End-Diastolic Dimensions
  • Blood Volume Increase by 10 to 50
  • Highest percentages with multiple fetal-placental
    units

10
MATERNAL CARDIOVASCULAR SYSTEM
  • Red Blood Cell Mass (Hematocrit)
  • Increases less than blood volume
  • Increase in erythropoietin and erythropoiesis
  • Physiologic Anemia of Pregnancy
  • Blood Volume Plasma Volume Red Blood Cell
    Mass
  • Vascular Reactivity Decreases
  • Increased metabolic clearance of vasoactive
    agents such as norepinephrine and angiotensin II
  • Decrease in alpha adrenergic receptors
  • Increase in vasodilators PGE2, PGI2, NO

11
MATERNAL CARDIOVASCULAR SYSTEM
  • Distribution of Cardiac Output
  • Sheep 3 to 4 Liters/min
  • Uterus 0.8 to 1.2 L/min
  • Uteroplacental Blood Flow (Percent of Cardiac
    Output
  • Ewe 8 at mid-gestation 16 in late gestation
    and 0.06 for nonpregnant uterus.
  • Women 17 at term
  • Mammary Blood Flow Increases from 0.2 in first
    trimester to 2 at term
  • Skin Blood Flow 100 increase over course of
    gestation

12
MATERNAL PULMONARY SYSTEM
  • Increased respiratory rate
  • Increase in tidal volume
  • Decrease in arterial pCO2
  • Increase in chest circumferance 5-7 cm in women
  • Decrease in bronchial/alveolar resistance

13
MATERNAL BLOOD COAGULATION INCREASES FROM 3
MONTHS TO TERM
  • Increased fibrinolytic cascade
  • Venous stasis thromboemolic events
  • Increase in platelet aggregation and formation of
    stable fibrin clots
  • Intrinsic from Cell Injury and Collagen damage
    increase in events beginning with Clotting Factor
    XII to platelet phospholipids and Ca to
    Fibrinogen and Clotting
  • Extrinsic (Rapid from Tissue placenta
    thromboplastin to go from Clotting Factor VII to
    Fibrinogen
  • Clotting mechanism increase rapidly at term

14
MATERNAL METABOLISM
  • Cost 77,000 to 81,000 kilocalories
  • 24 year old woman 56 kg
  • Gain 12.5 kg in pregnancy
  • 925 g protein
  • 3.83 kg fat
  • Fetus at term
  • 3.44 kg
  • 444 g fat
  • 543 g protein

15
MATERNAL METABOLISM
  • Pulmonary Ventilation increases 3 L/min
  • 20 increase in maternal O2 absorption into blood
  • Pregnant Uterus 25 ml O2/min
  • Pulmonary Muscles 10 ml O2/min
  • Heart 9 ml O2/min
  • Kidneys 5 ml O2/min
  • Mammary Glands 2 ml O2/min
  • Increasing Energy Intake Increases Appetite
  • Increase of 50 kcal/day first 34 weeks to 300
    kcal/day during last 30 days basal diet is 2,100
    kcal/day
  • Progesterone increases appetite
  • Increase in fat increases leptin

16
MATERNAL METABOLISM
  • Poor Nutrition
  • Smaller placentae by 20 to 30 and smaller babies
    by 200 to 300 g in first trimester
  • Increase in Nutrient Absorption by 0 to 3
  • Increased pancreatic/biliary secretions
  • Increased intestinal blood flow
  • Decrease in gut motility
  • Hypertrophy of gut epithelial lining
  • Increase in villous height
  • Increase in intestinal dilation
  • Increase in epthelial hyperplasia
  • Increase in Vitamin D and Ca aborption
  • Increase in iron aborption
  • Lactogenic hormones increase absorption of
    Vitamin D, Ca and H2O.

17
MATERNAL METABOLISM
  • Nutritional Priorities of Fetus and Mother
  • Maternal
  • Nervous System
  • Bone
  • Muscle
  • Fat

Fetal Demands Nervous System Bone Muscle Fat
18
MATERNAL METABOLISM
  • Poor Nutrition
  • Smaller placentae by 20 to 30 and smaller babies
    by 200 to 300 g in first trimester
  • Increase in Nutrient Absorption by 0 to 3
  • Increased pancreatic/biliary secretions
  • Increased intestinal blood flow
  • Decrease in gut motility
  • Hypertrophy of gut epithelial lining
  • Increase in villous height
  • Increase in intestinal dilation
  • Increase in epthelial hyperplasia
  • Increase in Vitamin D and Ca aborption
  • Increase in iron aborption
  • Lactogenic hormones increase absorption of
    Vitamin D, Ca and H2O.

19
MATERNAL METABOLISM
  • Physical Activity Decreases
  • Progesterone
  • Increase in sleep
  • Decrease in Anxiety

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23
Mammogenesis and Lactogenesis
  • Mammogenesis Growth of Mammary Gland
  • Lactogenesis
  • Stage I Milk Protein Synthesis
  • Stage II Milk Protein Synthesis and Secretion
  • Galactopoiesis sustained milk production

24
  • MAMMOGENESIS AND LACTOGENESIS
  • Mammogenesis Sex Steroid Hormones
  • Estrogen --Involved in lengthening and branching
    of ducts
  • Progesterone --Duct and ductule cell
    multiplication --Enlargement and/or widening
    -- Actually inhibits mammary growth at high
    levels
  • Progesterone Estrogen -- Causes lobuloalveolar
    development
  • Initiation of Lactation (Lactogenesis)
  • Ovarian and/or placental steroids decrease
    (Progesterone inhibits)
  • Placental Lactogen disappears
  • Lactogenic Complex
  • Prolactin, Glucocorticoids. Insulin or IGF-I
  • Milk-Ejection Reflex Oxytocin/Neuroendocrine
    Reflex
  • Suckling or other teat/udder stimulation causes
    release of oxytocin from neurohypophysis
  • Maintenance of Lactation (Galactopoesis)
  • Galactopoetic Complex
  • Prolactin (Not Cattle), GH, Insulin, Thyroid
    Hormone, Glucocorticoids

25
EVENTS PRECEDING PARTURITION
  • Final Maturation of Fetus and its
    Hypothalamic-Pituitary-Adrenal Axis
  • Initiation of Milk (Colostrum) Secretion
  • Expansion of Birth Canal
  • Nest Building (Prolactin)
  • Aggression (Prolactin)
  • Restlessness (Prolactin and Estrogen)
  • Initiation of Uterine Contractions
  • Parturition and Termination of Pregnancy
  • Bonding Between Dam and Offspring (Prolactin and
    Oxytocin)

26
Fig. 14-14
27
Fig. 14-13
28
Fig. 14-15
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31
Parturition in Mammals
  • Controlled by fetus
  • Congenital absence of Hypothalamic-Pituitary-Adren
    al Axis
  • Ewe consumption of Veratrum californicum on Days
    14-15
  • Delayed Parturition
  • Lambs up to Day 175 and 20 pounds or more some
    cases ewes died
  • Piglets taken at Day 125
  • Similar reports for calves taken by C-Section at
    very heavy weights, e.g., 200 lb

32
Parturition Sheep Model
  • Fetus
  • Hypothalamus
  • CRH
  • Anterior Pituitary
  • ACTH
  • Prolactin
  • Adrenal Gland
  • Cortisol and Corticosterone
  • Placenta
  • Progesterone decreasing, estrogen increasing due
    to C-21 Steroid 17 alpha hydroxylase enzyme
  • Maternal
  • Corpus Luteum
  • Progesterone and Relaxin (some species)
  • Anterior Pituitary
  • Prolactin and Growth Hormone
  • Posterior Pituitary
  • Oxytocin
  • Uterus
  • PGF2-alpha increasing

33
Hormonal Factors Associate with Parturition
  • Fetal Hypothalamic-Pituitary-Adrenal Axis
  • A. CRH Day 100 Fetal Life
  • B. ACTH Day 125 Fetal Life
  • C. Cortisol Production Dependent on Critical
    Mass of Adrenal Tissue
  • D. Cortisol Increases most rapidly 2 to 3 days
    before onset of labor and parturition
  • In pigs, adrenal weight increases along with
    circulating levels of cortisol most rapidly after
    Day 100 of the 114 day period of gestation

34
Hormonal Factors Associate with Parturition
  • Fetal Hypothalamic-Pituitary-Adrenal Axis
  • E. Cortisol
  • Stimulates rapid increase in C21 Steroid 17-alpha
    hydroylase enzyme for conversion of Progesterone
    to 17-alpha hydroxy Progesterone when then is
    metabolized to androgens and estrogens
  • P4 DECREASES RAPIDLY DUE TO CONVERSION OF
    PROGESTERONE TO ESTROGENS
  • Decrease sulfotransferase in endometrium so MORE
    UNCONJUGATED ESTROGENS
  • Stimulate PGF secretion

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Hormonal Factors Associate with Parturition
  • Oxytocin
  • Released in response to PGF and due to Ferguson
    Reflex of fetal pressure on cervix
  • Stimulates uterine contractions
  • Stimulates bonding between mother and offspring

37
Hormonal Factors Associate with Parturition
  • Relaxin
  • Molecular Weight 6,300 (6,000 to 10,000)
  • Pig From CL
  • Other species cow (CL, placenta), sheep (?),
    mare (placenta)
  • Cervical Relaxation
  • Acts with other hormones
  • Estrogens
  • PGF and PGE
  • Oxytocin

38
Hormonal Factors Associate with Parturition
  • Relaxin (continued)
  • Increases Keratin SO4 in cervical collagen
  • Decreases Dermatin SO4 in cervical collagen
  • With loss of Dermatin SO4 there is a decrease in
    cross-linking among collagen fibers and greater
    elasticity of connective tissue of cervix and
    pelvic ligaments to increase distinsibility of
    pelvic canal for birth of fetus
  • Role in lactation by stimulating growth and
    development of teat and possibly lactation
  • Ovariectomized pigs give birth, but dont lactate
    normally, so is relaxin critical to parturition?

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40
Hormonal Factors Associated with Parturition
  • Uterine Myometrial Contractions
  • Coordinated and Rhythmic Contractions of
    Myometrium
  • Involuntary Contractions of Abdominal Muscles
  • Dilation and Softening/Distensibility of Cervix
  • Myometrial Contractions
  • Increased synthesis of gap junctions (e.g.,
    Connexin 43) due to decreasing progesterone and
    increasing estradiol
  • Essential for strong coordinated contractions
  • Increase in cAMP associated with increase numbers
    of gap junctions
  • Increase in free Ca and its binding to
    calmodulin which activates myosin kinase
  • Myosin kinase ? Myosin-PO4
  • Myosin-PO4 Actin Contractions

41
Hormonal Factors Associate with Parturition
  • Uterine Myometrial Contractions (continued)
  • Increase in free Ca and its binding to
    calmodulin which activates myosin kinase
  • Myosin kinase ? Myosin-PO4
  • Myosin-PO4 Actin Contractions
  • Oxytocin lowers threshhold potential for action
    potential of myometrium and increases rate of
    Ca influx to stimulate contractions
  • PGF increases intracellular free Ca and
    frequency of contractions

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Inhibited at Parturition
Inhibited at Parturition
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11ß hydroxylase
11ß hydroxylase for corticosterone and cortisol
52
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53
Ovine
Human
Fetal Hypothalamic Pituitary Adrenal Axis
?
Fetal Glucocorticoid Production Corticosterone
and Cortisol
? Placental CRH
?
Placental Estrogens
?
?
?
Intrauterine Production of Prostaglandins
54
Challis et al. J Obstetrics and Gynecology
31492-499. Fetal Signals and Parturition
  • CRH is Produced by Human Chorion in response to
    cortisol from fetal adrenal
  • CRH stimulates Dehydroepianrosterone Sulfate
    (DHAS) from fetal adrenal that is converted to
    estrogens by chorion
  • Glucocorticoids and estrogens stimulate increased
    expression of prostaglandins E and F and
    decreases PGDF-15 that OTHERWISE inactivates PGs

55
Challis et al. J Obstetrics and Gynecology
31492-499. Fetal Signals and Parturition
  • Central Characteristics of Human Parturition
  • Increase in CRH and PGHS2 in chorion
  • Decrease in PGDH15
  • Increase in FP and EP prostaglandin receptors
  • Decreased sensitivity of uterus to progesterone
  • Increase in production of estrogens from DHAS by
    chorion
  • Increase in myometrial contractions

56
Challis et al. J Obstetrics and Gynecology
31492-499. Fetal Signals and Parturition
  • Conversion of Progesterone to Estradiol and Loss
    of Progesterone Influence
  • Increased Contraction Associated Proteins
  • Oxytocin Receptor
  • PGF Receptor
  • Connexion-43 Gap Junction Protein
  • Recent Suggestion that Increase in Progesterone
    Receptor C Isoform Results in Loss of
    Progesterone Responsiveness via PR Isoforms A and
    B in Human Myometrium (Condon et al. 2006 Mol
    Endocrinol 20764-775

57
Controlling Time of Parturition
  • Efficient use of labor and facilities to reduce
    neonatal death losses
  • Reduce length of gestation
  • Increase opportunities for cross-fostering
    neonates in event of failure of dam to accept
    offspring, cannabilism or failure to lactate
  • Convenience of producer
  • In swine, uniformity of post-weaning estrus

58
Controlling Time of Parturition (continued)
  • Swine Corticoids Ineffective
  • PGF-2 alpha 200 ug cloprostenol or 10 mg
    Lutalyse at 7 AM and 7 PM with farrowing 24-26 h
    later.
  • Should not be used prior to Day 112 of pregnancy
    due to decreased survival of neonate
  • Cows Corticoids, Estradiol and PGF are
    effective
  • 20 mg dexamethasone to dam most commonly used.
    For maximal survival of calf, cows should be
    within 1 week of term. Some countries with wet
    and dry season induce parturition to coincide
    with rainy season, high nutrient availability and
    focus on milk production with calves having
    little economic value
  • Retained placentae major issue

59
Controlling Time of Parturition (continued)
  • Mare Corticoids, PGF and Oxytocin
  • 2.5 mg PGF (Lutalyse) every 12 hours causes
    birth/abortion in late gestation.
  • 200 dexamethasone/day for 4 days with foals being
    born 72 to 96 h after end of treatment
  • 20 IU to 200 IU Oxytocin administered with
    estradiol will cause cervical dilation and birth
    in some cases.

60
Post-Partum Period
  • Cow
  • Days 0-12 Sloughing and Discharge of
    endometrial tissue and placenta
  • Days 25-30 Uterine Involution completed
  • Days 40-45 Uterus considered ready for next
    pregnancy
  • Dairy First estrus around Day 15 to 20 and
    breeding from Day 60
  • Beef First estrus between 60 and 100 days and
    breed during desired dates (spring or fall)

61
Post-Partum Period
  • Sheep
  • Uterus involuted by Days 25 to 30
  • Breed in fall
  • Pig
  • Uterine involution completed by Days 21 to 28
  • Breed at post-weaning estrus (3-7 days)
  • Mare
  • Foal Heat 5-15 days postpartum
  • Breed if no complications
  • Human
  • Highly variable and related to many factors
  • Suckling intensity, body condition, nutrition
    etc

62
Fetal to Neonatal Transition
  • Adjusting to Extra-Uterine Life

63
Fig. 14-14
64
Fig. 14-13
65
Fig. 14-15
66
Cardiovascular Function
  • Ductus Arteriosis Duct between Pulmonary Artery
    and Aorta that allows most blood to be shunted
    past the Pulmonary Artery and into Aorta. With
    increase in pO2 at birth, the Ductus Arteriosis
    closes and blood is forced to go to the lungs for
    oxygenation.
  • Foramen Ovale Valve (flap-type) that closes
    when pressure in left side of heart increases
    upon closure of the Ductus Arteriosis.

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72
ADULT
RIGHT HEART ? LUNGS ? LEFT HEART ? ?
AORTA ? LIVER ? ? ? BODY
FETUS
Lung
RIGHT HEART ? FORAMEN OVALE ? LEFT
HEART ? ? AORTA DUCTUS
ARTERIOSIS PLACENTA
BODY OF FETUS
Liver Ductus Venosus
73
Gut
  • Filled with Amniotic Fluid drunk at 500 ml/day
  • Contains meconium fecal material
  • Absorbs amino acids, sugars and electrolytes
  • Digestion of proteins, aborption of amino acids
    and incorporation into fetal tissues
  • Colostrum fluid phase pinocytosis and gut
    closure regarding absorption of immunoglobulins
  • Passive Immunity required for piglets and
    beneficial for offspring of all species
  • Gut maturation
  • IGF-I and EGF in colostrum stimulate gut
    maturation

74
Renal System
  • Normal fetus 450 ml urine/day into amniotic sac
    with turnover of 300 to 600 ml/h of amnionic
    fluid
  • Proteinuria in fetal life to closure of kidney
    tubules in neonate
  • Absence or malfunction of kidneys leads to death
    or retarded development

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Respiratory System
  • Fetal breathing occurs in utero
  • Allows development of intercostal muscles of
    chest and diaphragm associated with breathing

77
Fetal Adrenal Glands
  • Norepinephrine
  • Release of surfactant from epithelial cells of
    lung lobulo-alveolar structures
  • Absorption of liquid from lungs
  • Glucocorticoids (Cortisol and Corticosterone)
  • Lung maturation
  • Lactogenesis
  • Thyroxin to Triiodothyronine
  • Glucose storage as glycogen
  • Insulin secretion in response to glucose
  • Transition from fetal hemoglobin to adult
    hemoglobin
  • Closure of Ductus Arteriosis
  • Parturition

78
Lung Maturation
  • Synthesis and secretion of surfactant by lung
    alveolar epithelium
  • Glucocorticoids Synthesis (Transcription and
    Translation) of surfactant and storage in cells
  • Norepinephrine Secretion of surfactant
  • Surfactant essential for lung alveoli to maintain
    integrity and not collapse by providing high
    surface tension when stretched.
  • Fetuses deficient in surfactant develop Hyalin
    Membrane Disease and often die
  • Now Pediatricians have artificial surfactant to
    decrease risk of Hyalin Membrane Disease

79
Respiration
  • Umbilical Circulation
  • pO2
  • Artery 15
  • Vein - 25
  • pCO2
  • Artery 55
  • Vein 40
  • Maternal Uterine Circulation
  • pO2
  • Artery 95
  • Vein 35
  • pCO2
  • Artery 35
  • Vein - 45

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83
ADULT
RIGHT HEART ? LUNGS ? LEFT HEART ? ?
AORTA ? LIVER ? ? ? BODY
FETUS
Lung
RIGHT HEART ? FORAMEN OVALE ? LEFT
HEART ? ? AORTA DUCTUS
ARTERIOSIS PLACENTA
BODY OF FETUS
Liver Ductus Venosus
84
Postpartum Uterus
  • Uterine Involution and Repair

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92
).                                             
                                 
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95
11ß hydroxylase
11ß hydroxylase for corticosterone and cortisol
96
Ovine
Human
Fetal Hypothalamic Pituitary Adrenal Axis
?
Fetal Glucocorticoid Production Corticosterone
and Cortisol
? Placental CRH
?
Placental Estrogens
?
?
?
Intrauterine Production of Prostaglandins
97
Challis et al. J Obstetrics and Gynecology
31492-499. Fetal Signals and Parturition
  • CRH is Produced by Human Chorion in response to
    cortisol from fetal adrenal
  • CRH stimulates Dehydroepianrosterone Sulfate
    (DHAS) from fetal adrenal that is converted to
    estrogens by chorion
  • Glucocorticoids and estrogens stimulate increased
    expression of prostaglandins E and F and
    decreases PGDF-15 that inactivates PGs

98
Challis et al. J Obstetrics and Gynecology
31492-499. Fetal Signals and Parturition
  • Central Characteristics of Human Parturition
  • Increase in CRH and PGHS-2 in chorion
  • Decrease in PGDH-15
  • Increase in FP and EP prostaglandin receptors
  • Decreased sensitivity of uterus to progesterone
  • Increase in production of estrogens from DHAS by
    chorion
  • Increase in myometrial contractions

99
Challis et al. J Obstetrics and Gynecology
31492-499. Fetal Signals and Parturition
  • Conversion of Progesterone to Estradiol and Loss
    of Progesterone Influence
  • Increased Contraction Associated Proteins
  • Oxytocin Receptor
  • PGF Receptor
  • Connexion-43 Gap Junction Protein
  • Recent Suggestion that Increase in Progesterone
    Receptor C Isoform Results in Loss of
    Progesterone Responsiveness via PR Isoforms A and
    B in Human Myometrium (Condon et al. 2006 Mol
    Endocrinol 20764-775

100
Controlling Time of Parturition
  • Efficient use of labor and facilities to reduce
    neonatal death losses
  • Reduce length of gestation
  • Increase opportunities for cross-fostering
    neonates in event of failure of dam to accept
    offspring, cannabilism or failure to lactate
  • Convenience of producer
  • In swine, uniformity of post-weaning estrus

101
Controlling Time of Parturition (continued)
  • Swine Corticoids Ineffective
  • PGF-2 alpha 200 ug cloprostenol or 10 mg
    Lutalyse at 7 AM and 7 PM with farrowing 24-26 h
    later.
  • Should not be used prior to Day 112 of pregnancy
    due to decreased survival of neonate
  • Cows Corticoids, Estradiol and PGF are
    effective
  • 20 mg dexamethasone to dam most commonly used.
    For maximal survival of calf, cows should be
    within 1 week of term. Some countries with wet
    and dry season induce parturition to coincide
    with rainy season, high nutrient availability and
    focus on milk production with calves having
    little economic value
  • Retained placentae major issue

102
Controlling Time of Parturition (continued)
  • Mare Corticoids, PGF and Oxytocin
  • 2.5 mg PGF (Lutalyse) every 12 hours causes
    birth/abortion in late gestation.
  • 200 dexamethasone/day for 4 days with foals being
    born 72 to 96 h after end of treatment
  • 20 IU to 200 IU Oxytocin administered with
    estradiol will cause cervical dilation and birth
    in some cases.

103
Post-Partum Period
  • Cow
  • Days 0-12 Sloughing and Discharge of
    endometrial tissue and placenta
  • Days 25-30 Uterine Involution completed
  • Days 40-45 Uterus considered ready for next
    pregnancy
  • Dairy First estrus around Day 15 to 20 and
    breeding from Day 60
  • Beef First estrus between 60 and 100 days and
    breed during desired dates (spring or fall)

104
Post-Partum Period
  • Sheep
  • Uterus involuted by Days 25 to 30
  • Breed in fall
  • Pig
  • Uterine involution completed by Days 21 to 28
  • Breed at post-weaning estrus (3-7 days)
  • Mare
  • Foal Heat 5-15 days postpartum
  • Breed if no complications
  • Human
  • Highly variable and related to many factors
  • Suckling intensity, body condition, nutrition
    etc
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