Physiological changes in pregnancy

Question 1

What happens to O+P and LH/FSH in pregnancy?

Answer 1

Increased O+P produced by the placenta exerts negative feedback on LH and FSH production

Question 2

What happens to thyroid hormones in pregnancy?

Answer 2

Production of T3 and T4 increases due to B-hCG production - balanced by increased TBG production by liver so total T3 and T4 goes up but free active T3 and T4 is the same

Question 3

When does the fetal thyroid start working?

Answer 3

2nd trimester

Question 4

Why does insulin resistance increase in pregnancy?

Answer 4

Increased anti-insulin hormones (human placental lactogen, cortisol + prolactin) - reduce glucose uptake by mother to ensure supply to fetus

Question 5

What happens to blood pressure in pregnancy?

Answer 5

Decreases in 1st + 2nd trimesters then returns to normal by 3rd - progesterone causes vasodilatation

Question 6

What happens to cardiac output in pregnancy?

Answer 6

Overall increase by 30-50% due to increased HR + SV to supply the fetus

• 20% in 1st trimester
• 40% in 2nd trimester
• Huge increase in labour then drops to normal within 1h

Question 7

What happens to total blood volume in pregnancy?

Answer 7

Increases due to RAA activation (increased sodium + water retention)

Question 8

Why should women not lie flat on their back when pregnant?

Answer 8

Should lie in left lateral position - gravid uterus can compress IVC, reduce venous return, SV and CO - reduced blood supply to fetus

Question 9

What ECG changes are normal in pregnancy?

Answer 9

LAD
Small Q waves
Inverted T waves in lead III
ST depression
Atrial / ventricular ectopics

Question 10

What cardiac exam changes are normal?

Answer 10

Due to increased blood volume:
Systolic flow murmurs (diastolic are pathological until proven otherwise)
3rd heart sound
Bounding / collapsing pulse

Question 11

What happens to lung capacity in pregnancy?

Answer 11

Lung capacity remains the same - although uterus displaces diaphragm upwards, AP and transverse thorax diameters increase

Question 12

What happens to tidal volume and minute ventilation?

Answer 12

Increase to meet increased metabolic rate

Question 13

Why does oxygen demand increase in pregnancy?

Answer 13

Increased oxygen consumption (20%) and metabolic rate

Question 14

Why is reflux and NV more common in pregnancy?

Answer 14

Stomach displaced upwards, increasing intra-gastric pressure

Question 15

Why is constipation and gallstones more likely in pregnancy?

Answer 15

Progesterone relaxes smooth muscle, reducing gastric + biliary tract motility

Question 16

Why are UTIs more common in pregnancy?

Answer 16

Progesterone relaxes ureters + bladder muscle - urine stasis

Question 17

What happens to GFR in pregnancy?

Answer 17

Increases 50-60% - raised CO increases blood flow to kidneys

Question 18

Why are VTEs more likely in pregnancy?

Answer 18

Increased fibrinogen + clotting factors = increased clotting + decreased fibrinolysis

Question 19

Why is pregnancy a hypercoaguable state?

Answer 19

Theory is that this reduces risk of haemorrhage

Question 20

What happens to Hb in pregnancy?

Answer 20

Physiological dilutional anaemia - increased plasma volume but red cell mass (Hct) does not increase as much leading to dilution

Question 21

What happens to white cells in pregnancy?

Answer 21

Modest leukocytosis

Question 22

What is the most common haematological abnormality in pregnancy?

Answer 22

Thrombocytopenia (platelets <150)

• Gestational thrombocytopenia occurs in 70-80% in the late 2nd/3rd trimester. Usually >100
• ITP is 2nd most common cause - suspect if develops in 1st trimester then declines throughout. Usually <100

Question 23

What is ITP?

Answer 23

AI antibody production against GpIIb/IIIa on platelets = platelet destruction

Question 24

What happens to energy requirements in pregnancy?

Answer 24

• Increases minimally in 1st and 2nd

- 200kcal per day increased in 3rd trimester

Question 25

What happens to basal metabolic rate in pregnancy?

Answer 25

Increases by 15-20%

Question 26

What skin changes can occur in pregnancy?

Answer 26

• Hyperpigmentation (linea nigra, melasma in face, nipples, umbilicus)
• Spider naevi + palmar erythema (due to high oestrogen levels + hyperdynamic circulation)
• Striae gravidarum

Question 27

Why are back pain and pubic symphysis dysfunction common in pregnancy?

Answer 27

Relaxin causes increased ligamental laxity