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.
Is there net sodium retention? why/why not?
YES!
Sodium retention is promoted by: o Activation of the renin angiotensin system o Rise in aldosterone o Estrogen o Cortisol Sodium loss is promoted by: o Rise in glomerular filtration rate o Expanded plasma volume o Progesterone rise o Prostaglandin rise
does ADH increase or decrease during pregnancy?
The threshold osmolality for the release of ADH becomes lower and the plasma osmolality is logically lower. There is an increase in diuresis after delivery.
Is increased frequency of urination normal in the first 6 weeks?
YES.
What happens to minute ventilation (Tidal volume*Respiratory rate) ?
Increases by up to 50%. Tidal volume increases but respiratory rate is unaltered
What are some common respiratory changes?
-Minute ventiallation increases
-PaCo2 (partial pressure of arterial Co2) falls to about 30mmgHG at term
-Expansion of the thoracic cage
-Diaphragm is elevated
-Residual (functional) volumes falls by 20%
-Forced vital capacity and peak expiratory flow increases after 14-16 weeks
-FEV1 in unchanged
FVC% is higher in pregnant women
Is dysponea common?
Yes. Sometimes women will feel breathless in the alter stages of pregnancy thought to be caused by the central effect of progesterone. They aren’t actually hypoxic!
What is forced vital capacity and peak expiratory flow?
a) The maximum amount you can breath out in a single big breath
b) The fastest rate that you break out
BOTH INCREASE around 14-16 weeks
Why is maternal appetite stimulated?
- Progesterone is orexigenic (stimulates appetite)
- Pregnant women become resistant to leptin. Leptin is normally produced in fat cells and inhibits your appetite
When is morning sickness most common?
At the start of pregnancy. Vitamin B6 helps
There is a generalised ____ in gut motility?
Decrease. This results in a prolonged transit time of food and increased water absorption
Causes constipation
What is reflux and heart burn caused by>
Reduced lower oesophageal tone likely by progesterone’s relaxation effects
Which of these changes during pregnancy and how?
- Gallbladder contraction and volume
- Saliva secretion
- Iron and calcium reabsorption
- Liver size
- Position of small and large intestine
- Impaired contraction and increased volume
- Increased
- Increased
- UNALTERED
- Changed
What happens to metabolism during pregnancy?
Metabolic rate increases
What is the maternal energy store?
Fat
When must women be fed?
Regularly and very frequently to prevent ketosis
How much protein is retained full term?
About 500g
What happens to insulin and glucose levels?
Insulin secretions increase, but blood glucose falls in the 1st trimester. Insulin resistance develops in later pregnancy
