Physiology in Pregnancy

Question 1

what mechanical changes happen in pregnancy?

Answer 1

• With weight gain, more blood flow and enlarging foetus, centre of gravity no long over feet so person leans back to avoid falling over and curves of their spine change and this is why pregnant people are more prone to back pain during and after pregnancy
• Relaxin (hormone produced during pregnancy), oestrogen and progesterone all cause increased pliability and extensibility of connective tissue. Ligamentous joints become less stable. Symphysis pubis and sacroiliac joints are particularly affected to allow birth of the baby. Normal pubic symphysial gap is 4-5mm and increases by around another 3mm in pregnancy
• Joint loosening starts as early as 10 weeks and returns to normal 4-12 weeks post partum. By term there is increased load of 2.8 times the normal value when standing

Question 2

what change sin metabolism happen in pregnancy?

Answer 2

• Basal metabolic rate increases in pregnancy to ensure foetal growth
• Pregnancy is a time of relative insulin insensitivity

Question 3

how does fatigue change in pregnancy?

Answer 3

• Hormonal changes cause fatigue, mainly in first trimester

Question 4

how does heartburn/reflux change in pregnancy?

Answer 4

• Food moves slowly in stomach and there is a delay in emptying
• Hormones cause relaxation of LOS
• General anaesthetic is high risk in pregnancy as risk of aspiration is higher

Question 5

does oedema occur in pregnancy?

Answer 5

• 80% develop some oedema due to increased sodium and water retention

Question 6

what happens to breasts in pregnancy?

Answer 6

• Increase in size, vascularity and become warm, tense and tender
• Increase pigmentation of areola and nipple and secondary areola appears

Question 7

what thyroid changes occur in pregnancy?

Answer 7

• Need more levels of iodine
• Thyrotoxicosis (overactive throid) occurs in approximately 1 in 500 pregnancies. It is most often due to Graves disease which is an autoimmune disorder
• Hypothyroidism (underactive thyroid) affects approximately 1% of pregnancies. The fetus is dependent on maternal thyroid function until fetal thyroid function begins at around 12 weeks gestation. It is important to ensure good thyroid replacement prior to pregnancy

Question 8

what happens to the immune system in pregnancy?

Answer 8

• General state of immunosuppression to allow for foetal tolerance and therefore increases maternal susceptibility to infection

Question 9

what changes occur in pregnancy to the cardiovascular system?

Answer 9

• Heart has to work harder
• People with heart conditions may suffer complications during pregnancy
• Circulating blood volume increases
• Increased CO as SV increases (amount of blood pumped out by the ventricle with each beat), also increased HR
• Increased oxygen consumption as the myocardium is working harder so it uses more

Question 10

what changes occur to the cardiovascular system postpartum?

Answer 10

• Most changes return to normal by 3^rd month post delivery

Question 11

what changes happen to the respiratory system during pregnancy?

Answer 11

• Increased work and oxygen requirements

Question 12

what haematological changes occur during pregnancy?

Answer 12

• Blood volume increases by 50-70% and red cell mass by 40%
• Increase in plasma volume2-3 fold increase in iron
• Pregnancy is a hypercoagulable state. The factors which promote clotting increase, factors which reduce clotting decrease
• The risk of deep venous thrombosis in pregnancy is also increased by venodilation and reduced venous return increasing venous stasis in the lower limbs.
• Pulmonary embolus is one of the main causes of direct maternal mortality in the UK killing approximately 6-15 people per year in pregnancy or the puerperium.
• Pregnancy increases the risk of thromboembolism by 6x.

Question 13

what changes happen to the renal system during pregnancy?

Answer 13

• significant dilatation of the urinary collecting system due to relaxation of the smooth muscle of the ureter caused by progesterone as well as the mechanical compression by the growing uterus
• A physiological hydronephrosis can be seen and is usually more pronounced on the right
• Glomerular filtration rate and creatinine clearance increase by about 50% meaning that normal levels of urea and creatinine are much lower during pregnancy
• UTI more common

Question 14

1. A 35 week pregnant patient collapses in the antenatal clinic. Cardiac arrest is diagnosed.

To have any chance of success what must be done prior to administering CPR?

1. Baby must be delivered
2. Patient must be put on a right lateral tilt
3. The uterus must be manually displaced
4. Patient must be moved to a labour ward as caesarean section will be required if CPR unsuccessful after 3 minutes

Answer 14

C – you will not be able to resuscitate any person with a gravid (pregnant) uterus who is lying flat because of the reduction in cardiac output this causes

Question 15

1. Part of the antenatal check is a urinalysis. You notice that a patient has consistently had microscopic haematuria on the past 2 occasions. What would be your management?
2. Check for urinary infection and ensure no protein in the urine. If both are negative organise an ultrasound of the renal system and if negative refer to urology urgently.
3. Do nothing – because of increased renal blood flow during pregnancy there will often be traces of blood on urinlaysis.
4. Check for urinary infection and if negative refer to the urologists as the patient will require cystoscopy to exclude bladder pathology.
5. Check for urinary infection and ensure no protein in the urine. If both are negative and renal function normal, organise an ultrasound of the renal system and if also negative ask the GP to follow up postnatally – if haematuria is still present the patient will require referral to urology.

Answer 15

D – it is common so make sure no proteinuria, infection and renal ultrasound and function is normal and if so then the most likely cause is due to bleeding from small vessels in the dilated renal function

Question 16

1. A 24 week para 1 presents to the maternity unit with shortness of breath.

One of the diagnoses that must be considered is pulmonary embolus. In pregnancy there is an increased risk of venous thromboembolism because

1. When pregnant, people are much less active and put on a significant amount of weight
2. Clotting factors VIII, IX, and X decrease and Protein S and C levels decrease making blood hypercoagualable
3. After 20 weeks clotting factors VIII, IX and X increase
4. Venous stasis in the lower limbs is associated with venodilation and decreased flow that is more marked on the left. This increases the risk of DVT (deep venous thrombosis) during pregnancy particularly in the L limb.

Answer 16

D

Question 17

1. Explain the physiological anaemia of pregnancy.

Answer 17

Circulating blood volume increases by 50-70% and the red cell mass by 40% causing a physiological anaemia of pregnancy. This means that at 28 weeks a haemoglobin (Hg) of 105 g/L or above is considered normal (non pregnant reference range 120-160g/L) This is the physiological anaemia of pregnancy. Anaemia is the deficiency of red blood cells