6. Physiological adaptations to pregnancy Flashcards
give 2 reasons why cadiovascular changes occur in pregnancy
- increased needs of foetus: requires high nutrition/oxygen flow from 2nd T onwards
- increased blood flow to growing breasts, kidneys and GI tract (increased metabolism)
which cardiovascular changes occur in pregnancy and how are these stimulated
i) increase in plasma volume (by 40%, with 20% increased RBC mass), esp. during 2nd T - via increased ALDOSTERONE
ii) increased CO from 4.5 to 6 L/min via increased SV and HR - causing increased BP
iii) decreased TPR to compensate for increased volume and CO via PROGESTERONE mediated vasodilation - causing decreased BP
name 2 possible consequences of the cardiovascular changes on the heart
- cardiac palpitations caused by increased HR
2. LV hypertrophy caused by increased SV/CO - flow murmurs
why does venous distension/engorgement occur in pregnancy and what are the possible consequences of this
Venous distension/engorgement caused by: - increased plasma volume - progesterone-mediated vasodilatoin - compression of IVC by growing uterus causing decreased flow velocity and stasis... decreased venous return to heart (risk of HYPOTENSION if women lies down)... OEDEMA in lower limbs.
Long-term sequelae inc. HAEMORRHOIDS (swollen veins in rectum and anus, risk increased by straining from constipation and labour) and VARICOSE VEINS (swollen veins in legs and feet).
give 2 reasons why haematological changes occur in pregnancy
- prep. for blood loss in delivery
2. high haemoglobin flow required to meet foetal O2 demans, esp. later in pregnancy
which 2 haematological changes occur in pregnancy and how are these stimulated
- increased fibrinogen and factor VIII production by liver… hypercoagulable blood
- increased RBC mass induced by EPO stimulation, itself stimulated by increased placental chorionic somatomammotropin and progesterone
name 2 possible consequences of the haematological changes
- hypercoagulability (+ stasis) increases risk of blood clots and embolisms - DVT and PE
- anaemia due to sig. increased plasma volume (relative to RBC mass increase) and increased iron requirements
why is there increseased resp. drive in pregnancy
- increased O2 needs of foeto-placental unit
2. increased maternal metabolic rate
what is the maternal response to increased O2 requirements and which hormone stimulates this
increased progesterone causes increased resp. drive by acting directly on resp. centre and sensitising chemoRs to CO2 changes. increases:
- tidal volume
- minute ventilation
- O2 uptake
give 2 reasons why metabolic changes occur in pregnancy
- nutritional requirements of foetus
2. lactation after birth
name 3 factors causing metabolic changes in early and late pregnancy
- increased appetite and glucose diversion into fat synthesis in 1st 1/2 pregnancy - increased progesterone levels
- increased maternal insulin resistance in 2nd 1/2 pregnancy so that glucose available for foetus - via increased human placental lactogen, prolactin, glucose and cortisol
- increased lipolysis - increased maternal free fatty acid, ketone and TAG levels for use as alternative metabolic fuel
what is the effect of increased progesterone on the GI tract
causes GI SM relaxation:
- decreased colonic motility… constipation
- relaxation of LOS (+ stomach compression due to diaphragm elevation by growing uterus)… acid reflux
why are UTIs common in pregnancy
increased progesterone… dilation of ureters and relaxation of bladder muscles… urinary stasis - UTI predisposition
why is urinary incontinence common in pregnancy
support of growing uterus and increased weight of foetus weakens pelvic floor muscles
how is maternal immune tolerance to foetus maintained
human chorionic gonadotrophin (hCG) reduces levels of IgA, IgG and IgM - prevents rejection
