maternal adaptations to pregnancy Flashcards
what facilitates maternal adaptations?
Two-way communication between maternal and fetal tissues
pregnancy hormones
- placental hormones (steroid hormones - oestrogen/progesterone, protein hormones (HCG, HPL, CRH prolactin, oxytocin, relaxin, POMC, placental GH & ALP, human chorionic thyrotropin & ACTH, activin, inhibin, pregnancy specific B1 glycoprotein)
- subsequent effects on maternal endocrinology
what is HCG produced by and what are its functions?
produced by synctiotrophoblast
Marked rise first trimester then declines
Signals presence of blastocyst to mother
Maintainscorpus luteum
what are progestins produced by and the what are their roles?
produced by the corpus lute and then the placenta
Increases until just before labour
“Pro-gestational”……
- Smooth muscle relaxation (many effects, including peripheral vasodilation)
- Inhibits OTR expression
Increases maternal ventilation
Promotes glucose deposition in fat stores
Raises body temperature
what is the role of oestrogen and what are they produced by?
oestrogen are produced by the corpus lute and then the placenta
they increase just before labour Promotes changed in CV system alter carbohydrate metabolism - insulin resistance breast, nipple growth uterine blood flow, myometrial growth cervical softening increases oxytocin receptors in myometrium water retention thyroid mining globulin
what is the is the role of hPL/human chorionic sommatomammotropin? what is it produced by?
produced by syncytiotrophoblast
Increases throughout pregnancy, levels proportional to size of placenta
Lactogenic and stimulates growth
Converts mammary glands into milk-secreting tissue
Mobilises glucose from fat reserves
↑insulin secretion but
↓insulin’s peripheral effect (fatty acids and glucose diverted to the fetus)
what is the role of placental CRH?
Increases throughout pregnancy, overall CRH levels rise over 1000 fold.
Plays a role in timing of parturition, interacts with maternal and fetal HPA systems.
what is the role of prolactin and what is it produced by?
produced by anterior pituitary
Milk production (but ONLY when E and P have declined post-partum)
Increases throughout pregnancy - levels 10-20 x higher by term.
what is oxytocin produced by and what are its actions
posterior pituitary and placenta
Acts on uterus and breasts
Contraction of smooth muscle of uterus and PG production
Milk Ejection Reflex
what is relaxin produced by and what are its actions?
produced by CL, decidua and placenta
Secreted by corpus luteum, decidua and placenta
Facilitates remodelling of connective tissue of reproductive tract in preparation for labour.
why do physiological changes happen during pregnancy?
supply nutrients to the foetus
support amniotic fluid production
clear fetal waste products.
meet fetal and placental demands for glucose, amino acids and oxygen
adapt in preparation for labour - protect mum from CV insults at time of delivery
what happens during each menstrual cycle to rehearse pregnancy?
peripheral vasodilation and resultant haemodynamic changes occur occur during each luteal phase
what maintains pregnancy until placenta is formed?
Blastocyst HCG secretion prevents luteal regression
Corpus luteum synthesizes progestins until placenta is formed Placenta takes over E and P production from ~9/40
what are anatomical adapations of the uterus during pregnancy?
- 10 fold increase in weight and blood flow
- size: pear shaped organ around 10ml volume –> 5000ml volume
composition: muscle cell hypertrophy, increased elastic tissue, increased supportive fibrous tissue
mainly hypertrophy/hyperplasia in first half of pregnancy, then stretch effect
hypertrophy of uterine and ovarian vessels
orientation:straightens and dexrotates with increase in size
what are the anatomical adaptations to the cervix during pregnancy?
increased vascularity and oedema, softening
increase In cervical glands –>production of tenacious mucous plug
hyperplasia/eversion of endo-cervical epithelium
what are anatomical adaptations to the vagina during pregnancy?
- venous congestion –> blu/purple tinti(affects cervix too)
oestrogen –> increased glycogen deposition in epithelium –> increased lactic acid (protective)
what are the anatomical adaptations of the breasts during pregnancy?
lactiferous ducts and alveoli proliferate –> increase in size (cause by oestrogen and progesterone_
skin changes
colostrum produced
lactation (sudden drop in oestrogen and progesterone and increase in prolactin –> lactation)
suckling –> increased oxytocin –> milk ejection.
what systems are affected during pregnancy?
CV resp haematological/coagulation renal GI endocrine/metabolic immunological
what are CV adaptations during pregnancy?
HR - increases, up to 20% by 3rd trimester
SV increases
CO - increases very early in 1st trimester, plateaus, increases again at start of labour
TRP/SVR - falls
BP - falls until 24/40 then slowly recovers to normal values at term
plasma volume increases
what causes increase CO during pregnancy?
increased HR
decreased HR variability
Increased stroke volume
BP falls despite the increase in CO because of the marked fall in peripheral resistance
what does lowered total peripheral resistance lead to in pregnancy?
decreased after load –> perceived underselling –> activation of RAAS –> increased plasma volume >50% (and reduced plasma osmolality)
what is aortocaval compression?
From 20/40 gravid uterus is big enough to compress great vessels.
Supine position at term -> 30-50% reduction in CO.
May be asymptomatic or cause marked hypotension.
Reduces uteroplacental perfusion -> fetal distres
what is the uterine blood flow at term?
500-800ml/minute
◦ Blood loss can accumulate rapidly in postpartum haemorrhage
◦ Circulating volume only ~5000ml – identify & treat promptly!
what are the respiratory adaptations during pregnancy?
overall, less demand on respiratory than CV system
Patients with lung disease do relatively well in pregnancy unless severely affected
mechanism for changes
- increased oxygen consumption (around 16%) and Carbon dioxide production –> increase in tidal volume –> increase in ventilation –> decrease in pCO2
trigger unclear
progesterone possibly lowers threshold/increases sensitivity of respiratory centre to CO2
Tidal volume - increases Total lung capacity - decreases Vital capacity - non change inspiratory capacity - increases expiratory reserve volume - decreased residual volum - decreased functional residual capacity - decreased RR - no change
what are the mechanical changes in pregnancy?
uterus expands
Lower ribs flare (ligaments relax - hormonal effect)
diameter of chest increases
the diaphragm is raised by 5cm
chest wall compliance decreases
what facilitates efficient gas change in the foetus?
maternal pCO2 reduced to less than half of fetal pCO2
what are the haematological adaptations during pregnancy ?
blood volume expand around 45%
fluide redistribution: increased plasma and interstitial volume
red cell mass increases ( number and size) due to increased erythropeisis
Iron requirements go up
plasma volume increase is greater than red cell increase –> dilution anaemia of pregnancy
- haemoglobin and haematocrit fall
WCC rises, particularly neutrophils
T and B lymphocyte counts stable but decrease function –> increased susceptibility to some infections
platelet count unchanged
pregnancy is a hyper-coagulable state
pro-coagulation clotting factors increase
inhibitory clotting factors fall
highest risk for thromboembolism in postnatal period
VTE is consistently one of the comments causes of direct maternal death in the UK
what are renal adaptations during pregnancy ?
functional and structural adaptations occur - these support CV system adaptation
Structural : increased blood flow (kidneys increase 1cm in length)
increase progesterone (= increase in size of. collecting system)
compression from gravid uterus at pelvic brim –> physiological hydronephrosis (R>L) present in 80% of woman.
overall effect = mild obstruction/urinary stasis = increased infection risk
Functional adaptations:
Renal blood flow(35-60%)
Glomerular filtration rate(40-50%)
◦ Affects urea and creatinine
◦ Affects interpretation of timed urine collection
Glycosuria common in pregnancy (GFR and decreased resorption in distal tubules)
ResistancetoangiotensinIIdevelopsandRAAS generally activated
◦ -> Large increase in extracellular water and Na/H2O retention
what are the GI/metabolic adaptions
Progesterone effects:
◦ Relaxed lower oesophageal sphincter
+ pressure from uterus = reflux!
◦ Decreased gastric/intestinal motility
Gall bladder increases in size, empties slower -> degree of cholestasis
Progressive insulin resistance during 2nd
half of pregnancy: blood glucose, crosses
placenta readily.
◦ ?Due to hPL/cortisol
Lipids increase – can’t interpret bloods in pregnancy.
what immunological changes in pregnancy?
Shift from TH1 to TH2 immunological response
◦ Tolerance of fetus
◦ Susceptibility to infection
Influenza
◦ Amelioration of some TH1 mediated conditions e.g
Rheumatoid arthritis
what is the intra-partum physiology?
- each contraction expels 300-500ml of blood into circulation
increases venous return/preload
increases cardiac output
pain, valsalva, anxiety, and position also affect CO
epidural can stabilise changes in CO (less HR variation ) used early in some cardiac patients
Overall CO increases as labour progresses (15% latent phase, 30% active phase, 45% second stage - pushing, 80% third stage)
what are minor symptoms of pregnancy?
Nausea & vomiting Heartburn Backache Urinary frequency Haemorrhoids/constipation Leg cramps Oedema Breast tenderness Paraesthesia Varicose vein
