Physiology of Pregnancy Flashcards
During a pregnancy, how much does the mothers blood volume increase by?
40%
Why is there a 1L blood store in the maternal blood spaces of the placenta?
To prepare for blood loss during birth
How do pregnant women increase their blood volume?
1) Progesterone is able to stimulate components of the renin-angiotension-aldoesterone system (RAAS)
2) Therefore there is an increase in aldosterone which increases Na+ reabsorption in the kidneys
3) This causes more water to also be reabsorbed
4) Also, oestrogen increases angiotensin, which then increases aldosterone.
What effect does atrial natriuretic peptide (ANP) have on blood volume during pregnancy?
- During pregnancy there is a decrease in ANP
- Therefore, less sodium is excreted and so less water is excreted
What is dilatational anaemia?
When blood volume increases so much that it makes the Hb levels low
Why can dilatational anaemia occur in pregnant women even though red cell mass increases?
Although the red cell mass increases by 25%, the blood volume increase is higher.
What effect does the increase in use of Fe for Hb have on the body?
- Decreases the amount of ferritin (the protein that stores Fe in tissues)
- Increases in Fe absorption from the gut
When in pregnancy is there a need for Fe supplements to be taken?
Twin pregnancies
By how much does the delivery of blood to the uterus increase by?
3.5x
What is a hypercoaguble state?
When the chances of a blood clot are increased
Why can hypercoaguble states occur during a pregnancy?
It is a physiologically adaptive mechanism to prevent postpartum bleeding. There is an increase in:
- Fibrinogen
- Factor VIII
- Von Willerband factor
What effect does pregnancy have on white blood cell levels and concentration?
There is an increase in the total number of WBCs
Concentration stays the same because there is also an increase in blood volume
How much does the heart enlarge by during pregnancy and why does this occur?
12% and due to the increased venous return
Why can the heart sometimes shift upwards during pregnancy?
The uterus can push up against the diaphragm and this can have the potential of shifting the heart upwards.
What does progesterone do to blood vessels?
Vasodilation
What happens to maternal pO2 and pCO2 in pregnancy?
Maternal pO2 increases
Maternal pCO2 decreases
What is the benefit of a pregnant woman having a higher pO2?
Allows for an increase in O2 delivery to maternal tissues and also passive diffusion at the placenta.
Because foetal Hb (HbF) has a higher O2 affinity than adult Hb (HbA), it allows for maximum O2 delivery to the foetus.
Why is there an increased risk of UTI during pregnancy?
Progesterone leads to the dilation of the renal pelvis and ureters
What is creatinine?
Waste product from the breakdown of muscle
Why does GORD increase during pregnancy?
Because of the increase in abdominal pressure
What effect can progesterone have on the GI system?
Lowers gut motility and can cause constipation
How does sensitivity to insulin vary between the first and second trimester?
In the frist trimester, there is an increases sensitivity to insulin
In the second trimester, there is insulin resitance because cortisol, oestrogen and progesterone are all insulin antagonists - so blood glucose levels rise
Why is folate important for embryos?
It is involved in DNA synthesis, repair and regulation and so is important for rapid cell division.
What can a folate deficiency during pregnancy lead to?
Neural tube defects (NTDs)
