W8 - CHILDBIRTH AND LACTATION

Question 1

How do you estimate the date of delivery?

Answer 1

• Taken from the last normal menstrual period (LNMP) plus 280 days (9 months and 7 days) from the first day of the last menstrual period
• Ultrasound taken
  
  • +/- 3 days at 7 weeks
  • +/- 7-10 days at 18 weeks
  • +/- 3 weeks at term
    
    • Less accurate at estimating the due date later on due to the larger variation in the foetus

Question 2

What is the relevance of the estimated date of delivery?

Answer 2

• Overdue - placenta starts to degrade (bloody supply is compromised)
• Planning - stopping work, holidays, being close to hospital, elective caesarean
• Deciding when to induce labour in women with mildly raised blood repressure or past estimated delivery date
• Monitoring the development of the baby
• Interpreting antenatal screening
  
  • E.g. Down’s syndrome

Question 3

Define preterm, term and post term

Answer 3

• Preterm
  
  • Less than 37 completed weeks
• Term
  
  • 37-42 completed weeks
• Post term
  
  • More than 42 completed weeks
• Preterm delivery occurs in about 12% of births, but causes 70% neonatal morbidity and mortality

Question 4

Explain foetal maturation

Answer 4

• Survival of neonate is dependent on functional maturation of systems essential for extrauterine life
  
  • Organs that interface with the environment
    
    • E.g. Lungs, intestinal tract, immune system, skin
  • Organs that maintain homeostasis
    
    • E.g. Hypothalamic-pituitary axis, kidneys, liver, pancreas
• Glucocorticoids (cortisol) promotes functional maturation of key foetal organ systems
  
  • Surfactant production in lungs - allows to re-expand more easily
  • Activity of enzymes in intestine, retina, pancreas, thyroid, brain
  • Deposition of glycogen in liver (temperature regulation)
  • Na+K+ATPase activity in cortical tubules enabling Na+ reabsorption
• If preterm, give the baby cortisol to help develop the lungs

Question 5

What is the role of corticosteroids in lung maturation?

Answer 5

• Surfactant enables the alveoli in the lungs to remain expanded when the foetus is born and takes its first breath
• Rising foetal corticosteroids stimulate synthesis of surfactant in human lungs from about 18-20 weeks
• Surfactant is produced by cells lining alveoli
• Failure to secrete sufficient amounts seriously interferes with lung expansion
• Respiratory distress syndrome in premature births is due to insufficient corticosteroids

Question 6

What is the function of glucocorticoids?

Answer 6

• Have a role in initiating labour - exogenous steroids do not initiate labour in humans
• Corticotropin releasing hormone (CRH) from the placenta stimulates foetal hypothalamic-pituitary-adrenal axis and adrenals to produce large amounts of cortisol towards the end of pregnancy
• Positive feedback loop between foetal cortisol and CRH
• Both CRH and cortisol stimulate placenta to produce prostaglandins (PG)
• CRH also stimulates oestrogen production
• CRH from placenta causes positive feedback, rather than normal CRH (Which has a negative feedback effect)

Question 7

What is the function of prostaglandins?

Answer 7

• Prostaglandins (PGE2 an PGF2-alpha)
• Prostaglandins from myometrium/placenta/decidua
• In response to CRH, cortisol, oestrogen, oxytocin and contractions
• Very powerful at causing contractions - used therapeutically
• Also used to directly cause contractions and soften the cervix
• Positive feedback loop - causes stretch which gives positive feedback to produce more prostaglandins
• Probably also stimulates gap junctions in myometrium

Question 8

What is the function of oxytocin?

Answer 8

• From baby (decidual placenta) and mother pituitary (in response to stress/stretching/pain) and in response to oestrogen
• Oxytocin causes contractions and more prostaglandins
• Oxytocin directly increases Ca++ that can go into smooth muscle - lowers contraction threshold
  
  • Also increases influx into myometrial cells - lowers excitation threshold

Question 9

What is the function of oestrogen?

Answer 9

• An increase in number of oxytocin and prostaglandins receptors in uterine muscle
• Prepares uterus for contractions - changes in uterine muscle
  
  • Increases number of oxytocin and prostaglandin receptors in uterine muscle
  • Increases gap junctions and ion channels between smooth muscle cells - electrical connections between myometrial cells
• Probably stimulates both oxytocin and prostaglandin production by foetus/placenta
• Opposes the uterine relaxant action of progesterone
• Starts delivery

Question 10

What are the functions of progesterone?

Answer 10

• Does the opposite to oestrogen
• During pregnancy progesterone relaxes the uterus - involved in maintenance of pregnancy by inhibiting contractions
• Functional withdrawal of progesterone allows myometrial contractility
• Probably - by the end of pregnancy, uterine progesterone receptors decrease, and oestrogen receptors increase; and/or release of progesterone binding protein

Question 11

What is the function of relaxin?

Answer 11

• High concentration around delivery, no direct evidence of what it does
• Probably - causes cervical softening and relaxation of maternal pubic symphysis (and other pelvic joints and ligaments) in late pregnancy
• Maximum plasma concentration in women at 38-42 weeks gestation

Question 12

Explain the process of cervix dilation

Answer 12

• Process begins several days before parturition
• Cervix is mostly connective tissue (85-90%) and smooth muscle (10-15%)
  
  • Not very stretchy
• Cascade of events “ripen” cervix, driven by oestrogen, prostaglandins and relaxin
  
  • Inflammatory cytokines (IL-2 and IL-8) produced by placenta and cervical fibrocytes also play a role
    
    • Inflammatory cytokines attract and activate neutrophils to release metalloproteinases, collagenase, elastase and other non-specific proteolytic enzymes
    • Enzymes and prostaglandins act to soften collagen fibres and dilate cervix
• Myometrial contractions and foetus pushing against the cervix leads to further dilation
  
  • Has to stretch 10cm

Question 13

Explain the processes involved in childbirth

Answer 13

• Cervix softens and increases in elasticity
• Concurrently, the myometrium gains the capacity to contract forcibly and rhythmically
• Contractions are then maintained and increased levels of/increased responsiveness to prostaglandins and oxytocin
• All initiated by a hormonal cascade leading to birth
  
  • Contribution by fetoplacental unit
  • Role of placental CRH and foetal cortisol in both foetal maturation and initiating labour
  • Cause increase in estrogen and prostaglandin production
  • ‘Functional withdrawal’ of progesterone
  • Estrogen stimulates production of prostaglandins and oxytocin and their receptors, as well as changes in myometrium
  • Placental oxytocin stimulates contractions and also causes more prostaglandin release
  • Maternal pituitary also releases oxytocin in response to stress
  • Prostaglandins involved in contractions, cervical softening
  • Positive feedback cycle - maintenance of labour - oxytocin and prostaglandins

Question 14

What is preterm birth? What are some of its causes?

Answer 14

• Birth before 37 completed weeks of pregnancy
• Causes are mostly unknown, but include
  
  • Uterine over-distension
    
    • E.g. Twins
  • Infections
  • Antepartum haemorrhage
  • Previous preterm delivery
  • Smoking
  • Maternal diabetes/hypertension affecting placenta

Question 15

What are some methods to delay or induce labour?

Answer 15

• Delay labour
  
  • Anti-prostaglandins - stop contractions but can also harm the baby
  • B-agonists - to relax smooth muscle
  • Ca++ - further development of lungs and time for mother to move to a better delivery place
• Induce labour
  
  • Oxytocin - induce prostaglandins for contractions and Ca++ uptake into smooth muscle
  • Prostaglandins - stimulate contractions and soften cervix
  • Break amniotic membrane - mechanical pressure, inflammatory process to soften the cervix

Question 16

Explain the start of labour

Answer 16

• Full term
• Vertex presentation (head down), head flexed (narrowed part of head through the pelvis)
• Healthy baby
• Healthy prepared mother
• Delivery plans in place

Question 17

Describe the physical factors for a normal birth

Answer 17

• Passages are large enough for a baby to fit through
• Nothing in the way
• Baby is small enough to fit through
  
  • Size - average newborn weight is 3.2kg
  • Position - head first, head flexed
• Efficient co-ordinated contractions

Question 18

What are the signs of labour onset?

Answer 18

• Regular contractions
• Progressive cervical effacement and dilation
• Water breaking - rupture of membranes
• +/- “show” (release of blood stained mucous plug from cervix - unreliable sign)
• +/- rupture of membranes

Question 19

What are the stages of labour?

Answer 19

• Pre-labour
  
  • Cervix softens and becomes stretchable
• Stage 1
  
  • Start of regular contractions to fully dilated (approximately 10cm)
• Stage 2
  
  • Full dilation until delivery
• Stage 3
  
  • Until delivery of placenta

Question 20

What does APGAR score stand for? Explain its purpose

Answer 20

• APGAR - appearance, pulse, grimace, activity, respirations
• Scores of infant adaptation - how well the baby is adapting to being outside the womb
• Widely used assessment of the status of newborns
• Score at 1 minute, then 5 minutes
• Helps assess how well baby is adapting and response to any resuscitation
• Initial score does not predict outcomes of individual baby
• Scores
  
  • 7-10 - doing well, no resuscitation needed
  • 4-6 - may require assistance with breathing
  • 0-3 - more likely to need resuscitation

Question 21

What are the optimal conditions for labour?

Answer 21

• Healthy mother
• Healthy, full term foetus
• Informed and relaxed mother
• Trusting, collaborative relations between mother, family and medical staff
• Physical factors in place
  
  • Passages large enough to fit baby through
  • Nothing in the way
  • Baby small enough to fit through
    
    • Size (average weight - 3.2kg)
    • Position of the baby (head first, head flexed)
  • Head deep in pelvis
  • Head flexed forward so that
    
    • Hard, smooth occiput presents, stimulating oxytocin production and contraction
    • The head presents its narrowest diameter
  • Foetal head firmly applied to inside of cervix
  • Cervix starts to soften after being tightly closed for 40 weeks to hold baby in during pregnancy

Question 22

Explain the physiological preparation of the uterus and cervix during childbirth

Answer 22

• The job of the cervix for most of pregnancy is to stay closed and hold the baby in
  
  • Contractility inhibited until about 24 weeks by progesterone
• Being able to undergo labour requires
  
  • Uterine and cervical readiness - ability of uterus to contract and open cervix
  • Hormonal stimulation of contraction in a prepared uterus
  • Oestrogens reach their highest level
    
    • Myometrial cells - increase oxytocin receptors
    • Antagonise effect of progesterone on uterine muscles

Question 23

Explain the process of triggering labour

Answer 23

• Hormonal stimulation of contraction in a prepared uterus
• Whole process is not completely understood, but thought to be a combination of
  
  • Foetal cells producing oxytocin
    
    • Triggers placenta to produce prostaglandins
    • Stimulates highly oxytocin sensitive myometrium (both powerful uterine muscle stimulants)
    • Increasing uterine contractions
    • Maternal response because of physical and emotional stressors
    • Activation of hypothalamus - causes release from posterior pituitary

Question 24

Describe the first stage of labour

Answer 24

• Contractions
  
  • Beginning - Usually weak and lots of time apart (10-30 minutes)
  • Normal labour contractions become
    
    • More frequent
    • Stronger
    • Larger
    • More rhythmic and effective at opening cervix
  • By the end of the first stage, contractions are about 1 minute long and 2 minutes apart
  • While other muscles will return to their original size after contractions, uterine muscles shorten slightly - pushing the baby out and pulls up cervix
    
    • Causes cervix to dilate and efface

Question 25

Describe the second stage of labour

Answer 25

• “Pushing” stage
  
  • Cervix is fully dilated
  • Full dilation of cervix to delivery
    
    • No point in pushing when the cervix is not fully open as foetus will not fit through
  • Women have uncontrollable urge to push and assisted by conscious effort pushes the baby out of the vagina
  • All the way from crowning to delivery
  • Finishes when the whole baby is born

Question 26

Describe the third stage of labour

Answer 26

• Postpartum until the delivery of the placenta
  
  • Placenta separates from the uterine wall and delivered
  • Uterus contracts and clamps off uterine blood vessels that had ‘fed’ off the placenta
    
    • Caused by uterine smooth muscle criss-crossing
  • Post-partum haemorrhage
    
    • Blood flow to the uterus is quite extensive, so any problems in delivery of placenta can cause major bleeding

Question 27

Describe the initiation of labour and the orientation of the child

Answer 27

• Labour officially begins when the baby enters the pelvis
• True labour occurs when there are regular contractions and cervical dilation
• The widest part of the pelvic inlet - the baby moves through transversely - narrowest part of the head facing mother’s right
• Widest part of pelvic outlet - antero-posteriorly so baby lies with face facing mothers back and head flexed
• Head ‘crowns’, then the baby twists again on its side to that shoulders can be delivered one at a time
• Rest of the body slides out easily
  
  • Placenta clamped on each side and cut and the baby given to the mother
  • Slight pulling on cord to prompt the detachment of the placenta and delivery

Question 28

Describe the caring for a newborn

Answer 28

• Airway - sometimes stimulation may be needed
• Dry
• Warm - skin to skin
  
  • Wrap (including head)
• Sustenance - breast feed as soon as possible after birth
• Touching and love

Question 29

Describe some post-labour changes

Answer 29

• Marked shortening and contraction that shears off the placenta and stops bleeding
• Involutions
• Will take about six weeks until the body is back to normal

Question 30

Describe the circulatory changes from neonatal to foetal life

Answer 30

• Ductus arteriosus and foramen ovale (from inferior vena cava) bypass the non-functional lungs
  
  • This is able to happen as there is very low pressure in pulmonary resistance in the foetus
  • Foramen ovale bypasses the lungs by passing blood directly from the right atrium into the left atrium (not going to the ventricle, lungs and back)
• Ductus venosus allows blood to partially bypass the liver
• Circulation is different as a foetus - does not remove its own waste through the lungs or kidneys, but instead, the placenta provides a waste disposal site and oxygen supply
• At birth, the umbilical vessels, as well as the liver and lung bypasses are occluded

Question 31

Describe the temperature regulation of a foetus and at birth

Answer 31

• Foetus - mother regulates her and the baby’s temperature
  
  • After birth - the baby is wet and cold, and must be dried with a towel
• Maintaining its own temperature - non-shivering thermogenesis (brown fat deposits accumulated towards the end of development)

Question 32

Describe the regulation of glucose by the foetus and at birth

Answer 32

• Foetus - mothers blood glucose is the same as the foetus
  
  • Can arise problems associated with gestational diabetes
• Birth - must maintain its own through feeding and glycogen deposits in the liver

Question 33

Describe other changes that occur from feotus to birth

Answer 33

• Other changes are mostly induced by CRH/cortisol
• Respiration - surfactant
• Digestion - enzymes
• Kidney - enzyme activation/Na+ reabsorption

Question 34

Describe the anatomy of the breast

Answer 34

• Located over pectoralis major, between ribs 2-6
• Contain mammary glands (site of milk production) surrounded by fat lobules

Question 35

What are mammary glands?

Answer 35

• Modified sweat glands
  
  • Part of the integument system
• Each mammary gland is divided into 15-25 lobes - open to the nipples via a lactiferous duct
• Lobes are padded and separated by connective tissue and fat
  
  • This connective tissue forms suspensory ligaments that are well developed in the superior parts of the gland and attach to the muscle fascia and overlying skin
• Each lobe is subdivided into lobules that contain the milk-producing glandular alveoli
  
  • Milk passes from the alveoli to the lactiferous ducts and, via a lactiferous sinus, to the nipple
  • Lactiferous sinus accumulates milk during lactation

Question 36

Describe some changes during pregnancy

Answer 36

• Non-pregnant women - size of breast is largely determined by fat deposition
  
  • Duct and milk-producing system are small and non-functional
  • No secretory product in lumen
  • Myoepithelial cells surround the alveolar glands
• Pregnant - breasts undergo lobular hypertrophy so that lactation can occur following birth
  
  • Lobules fill with secretions
  • Breast secretes by budding off portions of cell cytoplasm
• Postpartum lactating - alveolar lumens filled with milk
  
  • Lipid droplets released by apocrine secretion
• Proteins and carbohydrates are released through exocytosis

Question 37

Describe the endocrine control of lactation

Answer 37

• Prolactin
  
  • Stimulates mammary growth
  • Increases milk synthesis from alveolar of mammary glands
• Oxytocin
  
  • No effect on growth
  • Allows for milk ejection
• Oestrogen
  
  • Stimulates proliferation of glandular tissue and ducts of breast, as well as prolactin release
  • However, it also blocks action of prolactin on the breast
• Progesterone
  
  • Stimulates proliferation of glandular tissue and ducts, but also blocks prolactin action
• hCS
  
  • Stimulates mammary growth
• hCG
  
  • Stimulates mammary growth

Question 38

Describe the contents of breast milk

Answer 38

• Milk varies depending on the time of day, in response to maternal nutritional status
• Colostrum is the yellowish fluid secreted during the first few days after birth
  
  • Contains less lactose than milk, almost no fat and more protein, vitamin A and minerals
  • Contains IgA antibodies - provide protection for infants digestive tract from bacterial infection
• Milk contains all nutrients necessary for the infant
  
  • 50% of baby’s caloric requirements come from fats and the protein in the milk
  • More easily digestible by the infant

Question 39

Describe the benefits of breast-feeding for the infant and mother

Answer 39

• For the infant
  
  • Iron, fats and amino acids are better absorbed as human milk does not curd in low pH environments (like cow’s milk)
  • Beneficial chemicals not found in cow’s milk
  • Natural laxative effects help cleanse bowels
• Mother
  
  • Bonding time with child