Physiology of women Flashcards
What is the normal body composition of women?
Water 52%
Fat 26%
At what body fat % does ovulation cease?
22%
At what body weight does amenorrhoea stop?
47kg
When do the physiological changes in pregnancy begin?
Mid-luteal phase of menstrual cycle
What systems are affected during the physiological changes of pregnancy?
Renal function and fluid homeostasis
CVS
Respiratory
GI/hepatic
Reproductive
Endocrine
Metabolic
Immune/defence
What is important about the physiological changes in pregnancy?
Anticipatory - preceded foetal demands/growth
In excess of foetal nutritional requirements
Dynamic - inter-trimester variation eg renal plasma flow
All enhance placental exchange of nutrients/waste - foetal appropriation of maternal resources
Resetting of normal physiological values NOT pathological
What happens with fluid retention in pregnancy?
30-50% increased in total plasma volume
ECF (plasma) volume expansion 1-2L
Influences renal and CVS function
Endocrine influence - ANP, ADH, RAAS, relaxin, progesterone
What electrolyte changes occur in pregnancy?
Na+ net retention around 900mmol (most abundant electrolyte in ECF)
- Changes oncotic pressure so increased vol of ECF
Increased K+ absorption (320mmol)
Increased natriuretic factors (progesterone and ANP) = loss of water
Increased anti-natriuretic factors (RAAS, aldosterone, deoxycorticosterone, oestrogen) = water retention = this is stronger and water is retained
What does the increased ECF have an effect on?
Dilution effects
Decreased plasma osmolality without diuresis - resetting of central osmostat in hypothalamus
- Around 10mosmol/kg H20
Decreased threshold for thirst - urge to drink at lower plasma osmolality
Decreased plasma oncotic pressure but no change in albumin levels (dilution effect)
- Facilitates generalised oedema
What happens to kidney size during pregnancy?
20% increase in size around term
What happens with kidney dilatation during pregnancy?
Dilation due to progesterone
Renal pelvis/calyceal systems dilate
Decreased ureteral tone/perisitalsis
Mechanical compression of ureters
- Hydronephrosis (right) 200-300ml
- Urinary stasis
Leads to increased UTI risk (pyelonephritis)
What happens with kidney blood flow and GRF during pregnancy?
Increased renal blood flow 50-60%
Renin angiotensin II increased resistance
Increased GFR 40-50%
Increased creatinine clearance
Glucosuria
Aminoaciduria
Filter permeability - pores change size/charge changes
Bowman’s capsule colloid oncotic pressure
What is eGFR used for clinically?
Modification of diet in renal disease formula
Many assumptions
Relies on serum creatinine level
Why can you not use eGFR during pregnancy?
Increased creatinine clearance
Decreased plasma creatinine
Not accurate during pregnancy
What happens to cardiac function during pregnancy?
Significant changes in BP
Increased HR seen around 5th week until term (10-20bpm) - due to increased sympathetic tone and decreased vagal tone to SAN
Increased stroke volume in early pregnancy (30%)
Increased cardiac output (30-50%)
What happens to BP changes during pregnancy?
Biphasic
- Early/mid pregnancy decreased - decreased peripheral vascular resistance (35%), peripheral vasodilatation
- Late pregnancy increased
Accurate recording essential during booking visit
What effect does increased ECF have on cardiovascular function?
Dilution anaemia
- Increased RBC < increased plasma volume
- Decreased Hb
- Decreased haematocrit
- Facilitates placental perfusion
Increased WCC polymorphonuclear leukocytes - no dilution effect seen
Blood hypercoagulable
- Increased plasma fibrinogen levels and increased ESR (low level of controlled inflammation)
- Increased clotting factors (VII, VIII, X)
- Increased plasminogen activator inhibitor (inhibits dissolving of clot)
- Increased risk thromboembolism including post-partum (6-7/12 post-partum)
Increased iron demand
What thoracic changes do you get during pregnancy?
Diaphragmatic elevation around 4cm
- Heart displaced upwards/left
- Apex moved laterally
- More horizontal position
- Increased pulmonary blood flow
Increased ventricular muscle mass (50%)
Increased size LV
What is the significance of the altered cardiac anatomy in pregnancy?
Normal variations in function/diagnostics
Altered HS - systolic/diastolic murmurs
Altered ECG tract
- Lead III - inverted T-wave
- Lead III/aVF - prominent Q-eave
- Altered QRS axis (left deviation)
What happens to O2 consumption during pregnancy?
Increased maternal O2 consumption
15-20%
NP around 250ml/min-300ml/min
What mechanical changes to respiratory system are there during pregnancy?
Thorax
- Diaphragmatic elevation
- Increased sub-costal angle
- Increased thoracic circumference
- Decreased chest compliance - lung compliance unchanged
Progesterone induced tracheo-bronchial smooth muscle relaxation
Changes in respiratory volumes
What biochemical changes in respiratory function do you get during pregnancy?
Increased tidal volume and increased minute volume
70% experience subjective dyspnoea
PCO2 falls from 4.7kPa -> 4.0kPa
Progesterone enhances respiratory centre chemoreceptor sensitivity
Increased 2,3 DPG in maternal erythrocytes
What is the double Bohr effect?
‘Bohr effect’
- Increased DPG binding so increased O2 at same PO2
- Increased plasma CO2 gradient (increased acidity)
- Favours O2 release at acidic pH
‘Double Bohr effect’
- Foetal erythrocytes Hb 2alpha:2gamma
- More erythrocytes compared to mother
- Low DPG affinity - favours O2 uptake at low placental PO2
- Gradient removes CO2 (becomes alkalotic) - favours O2 uptake at alkaline pH
What happens to the potential for respiratory alkalosis during pregnancy?
As mother blowing off a lot of CO2 = state of compensated respiratory alkalosis
Decreased H+:HCO3- ratio in kidney
PCT
- Complete titration of all filtered HCO3- but due to decreased PCO2 (more alkalotic) - incomplete titration of filtered HCO3-
- Excess filtered bicarb excreted in urine
- Renal compensation for excess HCO3-
- Pregnancy decreased HCO3- plasma
- Pregnancy - state of compensated respiratory alkalosis
What happens to the stomach during pregnancy?
Delayed gastric emptying
Cardiac sphincter relaxation - heart burn in around 81%
Anaesthetic risk - aspiration pneumonitis (Mendelson syndrome)
Decreased gastric pH (more acidic)
What happens to the liver during pregnancy?
Reduced secretion of CCK (stimulated by acid secretions from stomach and stimulates gall bladder contrations)
Reduced gall bladder motility - increased concentrated bile in gall bladder
Risk of gall stones
Exacerbate dyspepsia
Obstetric cholestasis
What happens to smooth muscle during pregnancy?
Generalised smooth muscle relaxation
Progesterone induced
Altered drug metabolism?
What happens to the bowel during pregnancy?
Gut transit time increased from 52 hours to 58 hours
- Small bowel enhanced nutrient uptake
- Large bowel increased water reabsorption - constipation
What is hyperemesis gravidarum?
Chronic pregnancy vomiting
What is ptyalism?
Sialorrhoea gravidarum
Sensation of excess salivation
What neurological/psychological changes occur in pregnancy?
Altered appetite
Pica - ingestion of non-nutritive substance
What happens to pharmacokinetics during pregnancy?
Decreased gastric emptying - stays in stomach for longer and exposed to strong acid for longer (affects drug activity?)
Increased gut transit time (may absorb more of it)
Decreased gastric pH (more acidic) - alters activity of drug
Altered cyt P450 activities (hepatic) - rapidly broken down/not at all
Increased GFR, decreased plasma albumin - dilution effect, may lose more drug as filtered out
Increased ECF volume, drug dilution? - do you need more drug to see the same effect?
What happens to metabolism during pregnancy?
Hyperlipidaemic
Glucosuric
Why do we worry about gestational diabetes?
Provided to foetus via maternal circulation
Transports 0.6mmol/min/g placental tissue
Carrier system saturates around 20mmol/L
- Foetal glucose directly related to mother’s
- No mechanism to limit uptake below saturation point
- Excess glucose can cause significant foetal harm
What happens to glucose levels during pregnancy?
Early pregnancy - maternal glycogen synthesis, fat deposition (building up nutrient reserve)
Late pregnancy - maternal insulin resistance (maternal glucose stays level stays higher for longer)
What happens to insulin during pregnancy?
Progressive rise in gestational insulin response - peak around 32 weeks but decreased maternal sensitivity observed (increased insulin for longer, response to resistance)
Maternal blood glucose levels falls after overnight fast
- Glycogenolysis and gluconeogenesis induced
- Increased in maternal free fatty acids and ketone bodies
Similar to starvation response
- Potential metabolic problems in labour, DKA
Significance/regulation unclear
How common is gestational diabetes?
Incidence 1-5% in UK
What are the risks of gestational diabetes to the mother?
x7 increased risk for T2DM later in life
Often not picked up before labour
Can cause serious maternal complications
What are the risks of gestational diabetes to the baby?
Macrosomia (large for gestational age)
Shoulder dystocia
Obesity and/or metabolic dysfunction which persists into adulthood
What is the maternal control of foetal development?
Foetal origins of adult diseases - in utero influences
- Subsequent physiological function
- Foetal adaptation to expected post-natal future environment
- Disease patterns in adult life
- Female foetus in poor uterine environment = risk to grandchild too as eggs present in female foetus already???
Big push for getting healthy before pregnancy
What happens to the uterus during pregnancy?
Increased uterine mass 46-1012g at term
Smooth muscle hyperplasia and hypertrophy
From 20 wks - potential to compress abdominal aorta and IVC
Appearance of uterine natural killer cells
- Control EVT (extra-villus trophoblast) function? - prevents too much invasion into maternal system
- Immune privileged
Decidual spiral arteries remodelled
- Endovascular invasion
What can failed endovascular invasion look like?
Invasion localised to decidua (shallow)
Reduced acquisition of maternal blood supply
What placenta mediated disease can you have associated with failed endovascular invasion?
Pre-eclampsia
Premature birth
Foetal growth restriction
Recurrent miscarriage
Placental abruption
What happens to the cervix during pregnancy?
Increased softness and vascularity with increased gestation
Blue tinge (oestrogen mediated)
- Chadwick’s sign
- Pooled blood in early pregnancy
What happens to the breasts during pregnancy?
Increased volume with increased gestation - around 565ml to 775ml at term
Fat deposition around gland tissue - increased gland duct numbers (oestrogen), increased gland alveoli numbers (progesterone + hPL)
Increased serum prolactin
Prolactin inhibited by oestrogen and progesterone during gestation - decreased oestrogen and progesterone after birth removes inhibition around 48 hours
Hence why midwives say ‘milk will come in in a couple of days’
What is a normal delivery?
Spontaneous onset, low-risk at start of labour and remaining so throughout labour and delivery
Infant born spontaneously in vertex position between 37 and 42 completed weeks of pregnancy
After birth mother and infant are in good condition
Birth without induction of labour, spinal or epidural analgesia, general anaesthesia, forceps or ventouse delivery, c-section or episiotomy
What occurs during the latent phase of labour?
Irregular contractions
Show mucoid plug
Can last 2-3 days
Cervix effacing and dilate (0-4cm)
Encouraged to stay at home
What is effacement?
AKA cervical ripening
Thinning of cervix
Begins as closed tube around 4cm protected by plug of mucus
After this, ready for active labour
How should you assess a woman in labour?
Presentation - the anatomical part of foetus which presents itself first through the birth canal
Lie - the relationship between the long axis of the foetus and the long axis of the uterus
Attitude - presenting part flexed or deflexed
Engagement - widest part of presenting part has passed through the brim of the pelvis
Station - relationship between lowest point of presenting part and ischial spines
When does active labour start?
At 4cm dilated
Regular contractions - 4 in 10
What non-pharmacological methods can reduce pain in labour?
Trained support
Hypnotherapy
Sensory methods - position/posture, hydrotherapy, TENS
Complementary - massage, acupuncture, reflexology, aromatherapy, homeopathy
What is the most widely used pharmacological pain relief and what are its pros and cons?
Entonox 50% N2O 50% O2
Rapid onset analgesia, minimal s/e
Self limiting
Green house gas
Theoretical risk of bone marrow suppression
What are the S/E of entonox?
N&V
What opiates can be used during labour and how are they delivered?
Pethidine/morphine/diamorphine (more potent)
Single shot usually IM
What are the foetal S/E of opiates during labour?
Respiratory depression
Diminishes breast seeking, breast feeding behaviours
Lipid soluble therefore cross placenta rapidly
Diamorphine eliminated rapidly by placenta
Pethidine metabolites can cause seizures
What are the maternal S/E of opiates during labour?
Euphoria/dysphoria
Respiratory depression
Pruritis
N&V
Longer 1st and 2nd stage labour
What are the maternal S/E of an epidural?
Increase length 1st and 2nd stage
Need for more oxytocin
Increased incidence malposition
Increased instrumental delivery rate
Loss of mobility
Loss of bladder control
Hypotension, pyrexia (but not increased risk of infection)
What are the foetal S/E of an epidural?
Tachycardia due to maternal temp
Diminishes breast feeding behaviours
What maternal observations need to be taken during labour?
BP
Pulse
Temp
Bladder
Contractions
Drugs
Vaginal examination
Eat and drink as norma
When does foetal monitoring take place for low risk women?
Intermittent monitoring for all low risk women - term, spontaneous
Every 15 mins 1st stage
After a contraction for 1 min
Describe the mechanism of labour
Descent
Flexion
Internal rotation
Crowning
Extension
Restitution
Internal restitution of shoulders
Lateral flexio
What happens in the 3rd stage of labour?
Physiological management - increased blood loss
Active management - oxytocic, cut and clamp cord, CCT
N&V
Check placenta and membranes complete
What are the benefits of delayed cord clamping?
For at least 1 minute post birth
Increased RBC, iron, and stem cells
Aids growth and development up to 6 months old
Reduced need for inotropic support
What is the menstrual period?
Monthly bleeding from reproductive tract induced by hormonal changes of menstrual cycle
Length of menstrual cycle is time from start of a period to start of the next
What is the length of a period?
2-8 days (mean 5 days)
What is the length of a cycle?
21-35 days (mean 28 days)
How much blood loss is normal during menses?
60-80ml
What is menorrhagia?
Heavy menstrual bleeding that occurs at expected intervals of the menstrual cycle
What is intermenstrual bleeding?
Uterine bleeding that occurs between clearly defined cyclic and predictable menses