Physiology of Pregnancy

Question 1

why are pregnant people prone to back pain during (+ after) pregnancy

Answer 1

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

Question 2

what do the hormones relaxin, oestrogen and progesterone cause during pregnancy

Answer 2

increased pliability and extensibility of connective tissue –> ligamentous joints become less stable. Esp pubic symphysis and sacroiliac joints to allow for childbirth

Question 3

what is normal symphyseal gap and by how much does it increase during pregnancy

Answer 3

4-5mm and increases by 3mm

Question 4

when in pregnancy does joint loosening start and when does it return to ‘normal’?

Answer 4

early as 10wks

4-12wks postpartum

Question 5

how does metabolism change during pregnancy

Answer 5

changes to ensure adequate nutrition for foetal growth. Basal metabolic rate increases

Question 6

what is fatigue in pregnancy likely due to

Answer 6

1st trimester: hormonal changes, tends to improve for 2nd trimester

3rd trimester: increased workload of advanced pregnancy and difficulty sleeping

Question 7

why do pregnant women get heartburn/reflux

Answer 7

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

Question 8

what causes oedema in pregnancy

Answer 8

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

Question 9

breast changes during pregnancy

Answer 9

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

Question 10

why is pregnancy associated with relative iodine deficiency

Answer 10

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

Question 11

why can hyperemesis gravidarum be associated with a biochemical hyperthyroidism

Answer 11

the beta sub-unit of BHCG is structurally very like TSH

get more T4 and less TSH

Question 12

what happens to immune system in pregnancy

Answer 12

in pregnancy there is a general state of immunosuppression to allow for foetal tolerance. this increases maternal susceptibility to infection

Question 13

why does heart need to work harder during pregnancy

Answer 13

growing foetus, weight gain, increased O2 requirements of uterus + breasts, heart must pump blood through utero-placental circulation

Question 14

what causes physiological anaemia of pregnancy

Answer 14

red cell mass increases by 40% causing a relative haemodilution

Question 15

why doe systemic vascular resistance fall in pregnancy

Answer 15

increased circulating vasodilators and diversion of blood into low pressure utero-placental unit

Question 16

why must a pregnant person never lie flat

Answer 16

IVC compression by uterus, lose 25% of CO

Question 17

what happens to tidal volume during pregnancy

Answer 17

increases

Question 18

what happens to resp rate in pregnancy

Answer 18

increases

Question 19

why is healthy pregnant person in state of compensated respiratory alkalosis

Answer 19

increased RR –> relative hyperventilation so PCO2 levels drop

Question 20

effect of enlarging uterus on diaphragm and lower thorax diameter

Answer 20

diaphragm pushed up (up to 4cm)

lower thorax diameter increase 2cm by splaying ribs

Question 21

what happens to functional residual capacity during pregnancy

Answer 21

reduces by approx 20-30%

Question 22

effect of increasing plasma volume on platelet count

Answer 22

causes relative decrease platelet count (though stays within normal range)

Question 23

Fe requirements during pregnancy

Answer 23

increase by 2-3 fold

Fe deficient anaemia most common haematological abnormality of pregnancy

Question 24

folate requirements in pregnancy

Answer 24

increase 20-30 fold (2nd most common cause preg anaemia)

Question 25

WCC + neutrophil count in pregnancy

Answer 25

increase

WCC up to 16x109 normal

Question 26

why is pregnancy hypercoaguable state

Answer 26

factors which promote clotting increase - factors Vii, IX, X and fibrinogen

factors reducing it decrease: proteins S+C, antithrombin 3 and fibrinolytic activity

Question 27

other than hypercoagubility, what else increases DVT risk in pregnancy

Answer 27

increased venodilation and reduced venous return leading to venous stasis in lower limbs

Question 28

why does urinary collecting system dilate

Answer 28

relaxation smooth muscle of ureter due to progesterone and compression by uterus

Question 29

why is there physiological hydronephrosis

Answer 29

increased blood volume and decreased systemic vascular resistance = increased renal plasma blood flow (80% in 2nd, 50% in 3rd)

Question 30

what happens to urea and creatinine levels

Answer 30

lower due to increased GFR and creatinine clearance

Question 31

excrete more or less protein?

Answer 31

more

Question 32

1st trimester

Answer 32

week 1-12

Question 33

2nd trimester

Answer 33

weeks 13-28

Question 34

3rd trimester

Answer 34

weeks 29-40

Question 35

intrapartum CVS changes: autotransfusion of contractions

Answer 35

with every contraction up to 500ml blood dumped in circulation

Question 36

intrapartum CVS changes: pain

Answer 36

increase circulating catecholamines, increase HR, BP and CO

Question 37

CO after delivery

Answer 37

increase by up to 80% due to lack of uteroplacental unit and relief of IVC compression