W8 - CHILDBIRTH AND LACTATION Flashcards
1
Q
How do you estimate the date of delivery?
A
- 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
2
Q
What is the relevance of the estimated date of delivery?
A
- 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
3
Q
Define preterm, term and post term
A
- 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
4
Q
Explain foetal maturation
A
- 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
- Organs that interface with the environment
- 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
5
Q
What is the role of corticosteroids in lung maturation?
A
- 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
6
Q
What is the function of glucocorticoids?
A
- 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)
7
Q
What is the function of prostaglandins?
A
- 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
8
Q
What is the function of oxytocin?
A
- 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
9
Q
What is the function of oestrogen?
A
- 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
10
Q
What are the functions of progesterone?
A
- 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
11
Q
What is the function of relaxin?
A
- 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
12
Q
Explain the process of cervix dilation
A
- 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
- Inflammatory cytokines (IL-2 and IL-8) produced by placenta and cervical fibrocytes also play a role
- Myometrial contractions and foetus pushing against the cervix leads to further dilation
- Has to stretch 10cm
13
Q
Explain the processes involved in childbirth
A
- 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
14
Q
What is preterm birth? What are some of its causes?
A
- 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
- Uterine over-distension
15
Q
What are some methods to delay or induce labour?
A
- 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
16
Q
Explain the start of labour
A
- Full term
- Vertex presentation (head down), head flexed (narrowed part of head through the pelvis)
- Healthy baby
- Healthy prepared mother
- Delivery plans in place
17
Q
Describe the physical factors for a normal birth
A
- 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
18
Q
What are the signs of labour onset?
A
- 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
19
Q
What are the stages of labour?
A
- 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
20
Q
What does APGAR score stand for? Explain its purpose
A
- 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
21
Q
What are the optimal conditions for labour?
A
- 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
22
Q
Explain the physiological preparation of the uterus and cervix during childbirth
A
- 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
23
Q
Explain the process of triggering labour
A
- 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
- Foetal cells producing oxytocin
24
Q
Describe the first stage of labour
A
- 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
25
Q
Describe the second stage of labour
A
- “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
26
Q
Describe the third stage of labour
A
- 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
27
Q
Describe the initiation of labour and the orientation of the child
A
- 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
28
Q
Describe the caring for a newborn
A
- 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
29
Q
Describe some post-labour changes
A
- 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
30
Q
Describe the circulatory changes from neonatal to foetal life
A
- 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
31
Q
Describe the temperature regulation of a foetus and at birth
A
- 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)
32
Q
Describe the regulation of glucose by the foetus and at birth
A
- 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
33
Q
Describe other changes that occur from feotus to birth
A
- Other changes are mostly induced by CRH/cortisol
- Respiration - surfactant
- Digestion - enzymes
- Kidney - enzyme activation/Na+ reabsorption
34
Q
Describe the anatomy of the breast
A
- Located over pectoralis major, between ribs 2-6
- Contain mammary glands (site of milk production) surrounded by fat lobules
35
Q
What are mammary glands?
A
- 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
36
Q
Describe some changes during pregnancy
A
- 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
37
Q
Describe the endocrine control of lactation
A
- 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
38
Q
Describe the contents of breast milk
A
- 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
39
Q
Describe the benefits of breast-feeding for the infant and mother
A
- 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
