Maternal Physiological Adaptations

Question 1

Explain how physiological anaemia of pregnancy occurs. (2)

Answer 1

Plasma volume increases from 5l to 7.5l, but RBC number does not increase, so haematocrit falls, leading to anaemia.

Question 2

Explain why you can get a normal S3 heart sound in pregnancy. (3)

Answer 2

Due to the dilation of blood vessels, the heart has to speed up to maintain cardiac output. This can lead to a mild hypertrophy of the left ventricle, meaning that the tricuspid and mitral valves will close at slightly different times, causing S3.

Question 3

Explained by blood pressure drops during pregnancy. (6)

Answer 3

Increased progesterone causes smooth muscle relaxation, which dilates blood vessels. This decreases vascular resistance, so decreases afterload on the heart, which decreases stretch, and decreases contractility, so the blood pressure will fall.

Question 4

Explain why pregnancy can cause oedema. (4)

Answer 4

Gravid uterus presses on the veins in the pelvis and the IVC. This can cause venous blood to back up in the legs, causing oedema as well as varicose veins and haemorrhoids. It can also cause hypotension because the return to the right atrium is reduced.

Question 5

Explain why a mother with aortic stenosis is at especially higher risk during pregnancy and birth. (3)

Answer 5

Hypotension from eg haemorrhage is dangerous because the already low LV filling is lowered even more, reducing cardiac output.

Question 6

Explain why pregnancy leads to urinary frequency and hydronephrosis. (4)

Answer 6

Gravid uterus presses on the bladder.
Increased blood flow to the glomerulus due to smooth muscle dilation increases GFR, meaning more urine is produced. This increased work will lead to a physiological hydronephrosis.

Question 7

Explain why the kidneys release more:
Renin
EPO
Calcitriol
During pregnancy.  (6)

Answer 7

Renin - retention of water - preparing for haemorrhage by having a larger blood volume, also need to supply foetus now.
EPO - tries to produce more red blood cells - combat physiological anaemia of pregnancy.
Calcitriol - holding onto more calcium - need it for foetal growth.

Question 8

Explain what happens to tidal volume during pregnancy. Explain the result of this and why this is a good thing. (4)

Answer 8

It increases because progesterone causes relaxation of the ligaments of the chest wall, bucket handle and the water pump movement are increased.
This decreases p(CO2) leading to a mild respiratory alkalosis, which enhances gas exchange with the placenta.

Question 9

Describe how the routine monitoring of an asthmatic during pregnancy should change. (2)

Answer 9

No change, peak flow and FEV1 should remain the same.

Question 10

Explain the cause of waddling gait often seen in pregnancy. (2)

Answer 10

Progesterone and relaxin loosen the sacroiliac joint and the pubic symphysis to prepare for birth, but this can cause pain leading to a waddling gait.

Question 11

Explain the GI symptoms pregnant women can experience. (4)

Answer 11

Constipation and bloating due to decreased peristalsis, caused by smooth muscle relaxation through progesterone.
Also relaxes the lower oesophageal sphincter, and with a gravid uterus increasing intra-abdominal pressure, this can lead to reflux.

Question 12

Explain why increased GFR in pregnancy could be dangerous. (2)

Answer 12

Increases creatinine clearance, could lead to AKI with normal creatinine clearance.

Question 13

Describe the functions of these hormones:
Progesterone (5)
Oestrogen (3)
Relaxin (2)
Oxytocin (2)
Prolactin (2)
Inhibin (1)
TSH (2;)

Answer 13

Progesterone: relaxes smooth muscle, slows gastric emptying, dilates vessels, increased GFR, increases core body temperature.
Oestrogen: breast tissue growth, water retention, protein synthesis.
Relaxin: softens the pelvic ligaments and cervix for birth.
Oxytocin: major role in birth and milk letdown.
Prolactin: stimulates breast development, promotes and maintains lactation post partum.
Inhibin: stops any more follicles maturing because inhibits FSH.
TSH: levels decrease in the first trimester due to high hCG (similar in structure, so stimulates increase T4 even with low TSH).

Question 14

Explain why pregnancy is classed as an immunocompromised state. (4)

Answer 14

To prevent rejection of the foetus, there is a reduction in cell-mediated immunity and T1 cytokines production. This is balanced by an increase in T2 cytokines and humoral immunity.
hCG reduces maternal IgA, IgG and IgM.

Question 15

Explain gestational diabetes and it’s consequences. (7)

Answer 15

Human placental lactogen causes insulin resistance, and if the mother was prediabetic before, can cause gestational diabetes.
Hyperplasia of the pancreatic beta cells and increased circulating insulin.
Causes foetal macrosomia - increased risk of: stillbirth, induction, Caesarian, perineal trauma, haemorrhage, shoulder dystocia, post delivery foetal hypoglycaemia (because the foetus has hyperinsulinaemia but no hyperglycaemia now).

Question 16

Explain how pre-eclampsia occurs (4), defining characteristics (3), risk factors (3) , symptoms (4) and treatments (2).

Answer 16

Defined as hypertension over 140/90 and proteinuria arising de novo after 20 weeks in a previously normotensive woman.
Caused by placental insufficiency caused by failed invagination of trophoblast on implantation, leading to an increased risk of foetal hypoxia.
To prevent this, the placenta raised systemic blood pressure which can cause kidney damage and proteinuria.
Risk factors: >40, obesity, personal or family history.
Symptoms: headache, visual disturbances, hyperreflexia, oedema, seizures.
Treatment: delivery of bab or antihypertensives.