Lecture 12: Maternal Physiology Flashcards
What peaks in early pregnancy and is tested in the pregnancy test?
hCG
What hormones increase with gestational age?
hPL and PRL (Human placental lactogen and prolactin)
hCG is a glycoprotein that is secret by trophoblasts of the implanting conceptus and has two subunits: a and b. What other hormone is its function similar to?
LH.
Function:
It maintains the corpus luteum in early pregnancy (continues progesterone and oestrogen. It promotes steroidogenesis in the fetoplacental unit after the placenta takes over the corpus luteum
If there are no lines on a pregnancy test, the test is _______?
Broken
How much weight does a woman gain on average during pregnancy?
13.5kg
What are the changes in blood volume and composition?
TOTAL BLOOD INCREASES= 1.5 litres (30-40%) by week 34
- Plasma increases=1.25L (45%)
- Red cell mass increases (240ml or 400ml)
- Drop in haematrocrit
- White blood cells increase to fight infection
- Platelet turnover increases
- Total plasma proteins increase overall (but concentration falls to 5.5-6g/100ml). ALBUMIN CONCENTRATION DROPS
What are the consequences of the drop in albumin concentration?
Colloid osmotic pressure falls (the pressure due to proteins that helps retain pressure in the capillaries)
Glomerular filtration rate increases
Oedema predisposition (due to reduced osmotic pressure, fluid is more likely to leave the vessels)
o Globulins increase
Thyroid binding globulin, corticosteroid binding globulin, angiotensinogen, transferrin—all stimulated to be produced by estrogen
What are the advantages and disadvantages of blood clotting more?
Advantages:
I. Less likely to haemorrhage post-delivery
II. Less likely to have a massive bleed if the placenta becomes detaches
Disadvantage:
I. More likely to get clots in the legs (i.e. DVT)
II. Thrombotic embolism
How much does cardiac output increase?
By about 1.5L/min (mostly by 16 weeks and plateau in late pregnancy)
What happens to blood pressure and why?
Falls in med pregnancy, rises to normal at term. This occurs because total peripheral resistance falls due to vasodilation mediated by Estrogen, progesterone and prostaglandins.
Is venous pressure in the lower limbs increased or decreased?
Increased (haemodynamic effect)
What is supine hypotension and why do pregnant women get it? What should be done?
Low blood pressure when lying flat on the back.
WHY:
Pregnant uterus falls down upon the inferior vena cava and obstructs flow - can cause fainting and discomfort
WHAT SHOULD BE DONE?
Pregnant women should lie on side, not back. Should be left side (20% increase in CO), right side (10% increase in CO).
Where does blood flow not change?
Brain, skeleton and gut
How much does GFR increase, and why?
50% due to the increased renal plasma flow (RPF) of 45% by relaxin hormone, and reduce in COP
What is glycosuria?
Glucose in the urine. Because the filtration rate is so high, you can filter out more glucose than can be reabsorbed.
o may occur if the filtered glucose load exceeds re-absorptive capacity - can be normal in pregnancy. Indicative of diabetes melitus in non-pregnant.