Physiology of Pregnancy Flashcards
why are pregnant people prone to back pain during (+ after) pregnancy
due to weight gain, increased blood volume + enlarging foetus, centre of gravity no longer falls over feet. to avoid falling over they must lean backwards and the curves of the spine change along it’s whole length
what do the hormones relaxin, oestrogen and progesterone cause during pregnancy
increased pliability and extensibility of connective tissue –> ligamentous joints become less stable. Esp pubic symphysis and sacroiliac joints to allow for childbirth
what is normal symphyseal gap and by how much does it increase during pregnancy
4-5mm and increases by 3mm
when in pregnancy does joint loosening start and when does it return to ‘normal’?
early as 10wks
4-12wks postpartum
how does metabolism change during pregnancy
changes to ensure adequate nutrition for foetal growth. Basal metabolic rate increases
what is fatigue in pregnancy likely due to
1st trimester: hormonal changes, tends to improve for 2nd trimester
3rd trimester: increased workload of advanced pregnancy and difficulty sleeping
why do pregnant women get heartburn/reflux
hormones cause relaxation of LOS meaning contents or stomach more likely to reflux back into oesophagus. ALso pressure frmo enlarging uterus and delayed gastric empytimg in pregnanyc
what causes oedema in pregnancy
physiological sodium and water retention and decreased ability to excrete a sodium + water load
also, increased blood volume and IVC compression contribute to peripheral oedema
breast changes during pregnancy
increase in size + vasculatiry
increased pigmentation of areola + nipple and 2ndary areola appears
montgomery tubercles appear on areola, colostrum like fluid can be expressed from end 3rd month
why is pregnancy associated with relative iodine deficiency
maternal iodine requirements increase as iodine is actively transported to the foeto-placental unit and urinary iodine excretion doubles due to increased glomerular filtration rate and decreased renal tubular reabsorption
why can hyperemesis gravidarum be associated with a biochemical hyperthyroidism
the beta sub-unit of BHCG is structurally very like TSH
get more T4 and less TSH
what happens to immune system in pregnancy
in pregnancy there is a general state of immunosuppression to allow for foetal tolerance. this increases maternal susceptibility to infection
why does heart need to work harder during pregnancy
growing foetus, weight gain, increased O2 requirements of uterus + breasts, heart must pump blood through utero-placental circulation
what causes physiological anaemia of pregnancy
red cell mass increases by 40% causing a relative haemodilution
why doe systemic vascular resistance fall in pregnancy
increased circulating vasodilators and diversion of blood into low pressure utero-placental unit
why must a pregnant person never lie flat
IVC compression by uterus, lose 25% of CO
what happens to tidal volume during pregnancy
increases
what happens to resp rate in pregnancy
increases
why is healthy pregnant person in state of compensated respiratory alkalosis
increased RR –> relative hyperventilation so PCO2 levels drop
effect of enlarging uterus on diaphragm and lower thorax diameter
diaphragm pushed up (up to 4cm)
lower thorax diameter increase 2cm by splaying ribs
what happens to functional residual capacity during pregnancy
reduces by approx 20-30%
effect of increasing plasma volume on platelet count
causes relative decrease platelet count (though stays within normal range)
Fe requirements during pregnancy
increase by 2-3 fold
Fe deficient anaemia most common haematological abnormality of pregnancy
folate requirements in pregnancy
increase 20-30 fold (2nd most common cause preg anaemia)
WCC + neutrophil count in pregnancy
increase
WCC up to 16x109 normal
why is pregnancy hypercoaguable state
factors which promote clotting increase - factors Vii, IX, X and fibrinogen
factors reducing it decrease: proteins S+C, antithrombin 3 and fibrinolytic activity
other than hypercoagubility, what else increases DVT risk in pregnancy
increased venodilation and reduced venous return leading to venous stasis in lower limbs
why does urinary collecting system dilate
relaxation smooth muscle of ureter due to progesterone and compression by uterus
why is there physiological hydronephrosis
increased blood volume and decreased systemic vascular resistance = increased renal plasma blood flow (80% in 2nd, 50% in 3rd)
what happens to urea and creatinine levels
lower due to increased GFR and creatinine clearance
excrete more or less protein?
more
1st trimester
week 1-12
2nd trimester
weeks 13-28
3rd trimester
weeks 29-40
intrapartum CVS changes: autotransfusion of contractions
with every contraction up to 500ml blood dumped in circulation
intrapartum CVS changes: pain
increase circulating catecholamines, increase HR, BP and CO
CO after delivery
increase by up to 80% due to lack of uteroplacental unit and relief of IVC compression
