Physiological changes in pregnancy Flashcards
What happens to O+P and LH/FSH in pregnancy?
Increased O+P produced by the placenta exerts negative feedback on LH and FSH production
What happens to thyroid hormones in pregnancy?
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
When does the fetal thyroid start working?
2nd trimester
Why does insulin resistance increase in pregnancy?
Increased anti-insulin hormones (human placental lactogen, cortisol + prolactin) - reduce glucose uptake by mother to ensure supply to fetus
What happens to blood pressure in pregnancy?
Decreases in 1st + 2nd trimesters then returns to normal by 3rd - progesterone causes vasodilatation
What happens to cardiac output in pregnancy?
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
What happens to total blood volume in pregnancy?
Increases due to RAA activation (increased sodium + water retention)
Why should women not lie flat on their back when pregnant?
Should lie in left lateral position - gravid uterus can compress IVC, reduce venous return, SV and CO - reduced blood supply to fetus
What ECG changes are normal in pregnancy?
LAD Small Q waves Inverted T waves in lead III ST depression Atrial / ventricular ectopics
What cardiac exam changes are normal?
Due to increased blood volume:
Systolic flow murmurs (diastolic are pathological until proven otherwise)
3rd heart sound
Bounding / collapsing pulse
What happens to lung capacity in pregnancy?
Lung capacity remains the same - although uterus displaces diaphragm upwards, AP and transverse thorax diameters increase
What happens to tidal volume and minute ventilation?
Increase to meet increased metabolic rate
Why does oxygen demand increase in pregnancy?
Increased oxygen consumption (20%) and metabolic rate
Why is reflux and NV more common in pregnancy?
Stomach displaced upwards, increasing intra-gastric pressure
Why is constipation and gallstones more likely in pregnancy?
Progesterone relaxes smooth muscle, reducing gastric + biliary tract motility
Why are UTIs more common in pregnancy?
Progesterone relaxes ureters + bladder muscle - urine stasis
What happens to GFR in pregnancy?
Increases 50-60% - raised CO increases blood flow to kidneys
Why are VTEs more likely in pregnancy?
Increased fibrinogen + clotting factors = increased clotting + decreased fibrinolysis
Why is pregnancy a hypercoaguable state?
Theory is that this reduces risk of haemorrhage
What happens to Hb in pregnancy?
Physiological dilutional anaemia - increased plasma volume but red cell mass (Hct) does not increase as much leading to dilution
What happens to white cells in pregnancy?
Modest leukocytosis
What is the most common haematological abnormality in pregnancy?
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
What is ITP?
AI antibody production against GpIIb/IIIa on platelets = platelet destruction
What happens to energy requirements in pregnancy?
- Increases minimally in 1st and 2nd
- 200kcal per day increased in 3rd trimester
