St A - Maternal Physiological Changes in Pregnancy

Question 1

What are the normal anatomic changes to the uterus during pregnancy?

Answer 1

• Weight gain of about 12.5kg, 6kg uterus.
• Pressure on IVC which will impede venous return from lower limbs (oedema)
• Combined relaxation of vessels and valves results in varicose veins

Question 2

What are the normal musculoskelteal changes to a women during pregnancy

Answer 2

• Accentuated lumbar lordosis due to change in centre of gravity. (backache, anterior flexion of neck and waddling gate),
• Relaxin causes softening of ligaments (sacroiliac and pubic symphysis pain),
• Diastasis recti (abdominal splitting)
• Striae gravidarum (stretch marks)

Question 3

Describe features of human chorionic gonadotrophin hormone

Answer 3

• Peptide hormone which is synthesised by trophoblast cells under direction of progesterone and oestrogen. It prevents involution of corpus luteum. Thought to cause the nausea and vomiting experienced by women

Question 4

Describe features of the human placental lactogen hormone

Answer 4

• Synthesised by syncytiotrophoblast cells of placenta,
• Promotes development of maternal mammary glands.
• Decreases insulin sensitivity and utilization of glucose by mother,
• Plays a role in release of free fatty acids from mother’s fat stores.

Question 5

What are the functions of oestrogens?

Answer 5

• Enlargement of mothers uterus, enlargement of mother’s breasts and growth of ductal structure, enlargement of external genitalia.
• Relaxation of pelvic ligaments (helps widen pelvis)

Question 6

What is the function of progesterone?

Answer 6

• Development of uterine endometrium and role in nutrition of early embryo.
• Decreases contractility of pregnant uterus which reduces risk of spontaneous abortion.
• Helps oestrogen prepare mothers breasts for lactation

Question 7

Explain why the placenta is an imperfect endocrine organ

Answer 7

• Cannot produce adequate cholesterol,

- Lacks 2 critical enzymes for synthesising oestrone and oestradiol as well as lacking the enzyme to synthesis oestriol.

Question 8

Describe features of the maternal-placental-foetal unit

Answer 8

• Mother supplies most of cholesterol as LDL particles.
• Foetal adrenal gland and liver supplies.
• Foetus cannot synthesis oestrogens as it lacks enzymes to catalyse the last 2 steps

Question 9

Explain brain changes induced by pregnancy hormones

Answer 9

Medial preoptic area plays central tole in regulating maternal behaviour. It is stimulated by oestrogen, progesterone and prolactin.

Question 10

Explain the cardiac output changes in pregnancy

Answer 10

• Increase in cardiac output in 1st trimester and then slow increase in the 2nd and 3rd. Occurs due to increase in SV and HR.

Question 11

How does the MAP change in pregnancy?

Answer 11

Usually decreases in 2nd trimester and then increases in 3rd trimester although it remains at or below normal. This is due to a decrease in peripheral vascular resistance due to the vasodilating effects of progesterone and estradiol

Question 12

Explain the changes in blood volume

Answer 12

Maternal blood volume increases during pregnancy due to increase in plasma volume and increased number of erythrocytes. This may be due to a decrease in renal perfusion. hCG may also increase the sensitivity of osmoreceptors.

Question 13

Explain the endothelial changes during pregnancy

Answer 13

High oestrogen levels stimulate NO production.

- Relaxin from corpus luteum causes vasodilation by blocking endothelin induced vasoconstriction

Question 14

Describe the haemostasis changes in pregnancy

Answer 14

Hypercoagulable state due to increase in coagulation factors, a decrease in the inhibitor of blood coagulation and an increase in fibrinolysis.

Question 15

What are some normal CVS examinationfindings that are different in pregnancy

Answer 15

• Peripheral oedema,
• Mild tachycardia,
• Jugular venous distention,
• Lateral displacement of left ventricular apex

Question 16

What is pre-eclampsia

Answer 16

Placental problem involving increase in BP, proteinuria and oedema. Occurs due to constriction of maternal spiral arteries. Treatment is delivery of baby

Question 17

What are the risk factors for pre-eclampsia?

Answer 17

• Previous pregnancy with pre-eclampsia,
• Over 40years old,
• Family history,
• Obesity,
• Primigravida (first pregnancy)

Question 18

What are the clinical features of pre-eclampsia?

Answer 18

Head aches, visual disturbances, epigastric pain and oedema

Question 19

What is eclampsia and what are some interventions?

Answer 19

Extreme hypertension (180/120) which can cause increased intracranial pressure, seizure and comas.
Interventions - magnesium sulphate, antihypertensives, rapid delivery and careful fluid balance.

Question 20

What are the respiratory changes in pregnancy?

Answer 20

Increase in alveolar ventilation due to an increase of the level of diaphragm due to relaxing effects of progesterone. Results in increase in tidal volume rather than resp rate

Question 21

What are some acid base changes in pregnancy?

Answer 21

Respiratory alkalosis to maintain maternal pH at 7.40-7.45 (bicarb excreted). This results in a slightly reduced ability to buffer metabolic acid load.

Question 22

What are some of the respiratory examination findings in pregnancy?

Answer 22

The spirometry parameters remain unchanged so any abnormal results are due to underlying respiratory disease

Question 23

What are some changes to the kidneys and urinary tract in pregnancy?

Answer 23

• Increased BF to kidney which increases GFR and therefore there is increased urine production (also due to increased fluid intake).
• Bladder compressed by foetus and expanding uterus,
• Bladder loses tone (due to preogesterone) so pregancy causes frequency, urgency and sometimes incontinence.
• Ureters dilated.

Question 24

Describe the changes in ion absorption and the changes in biomarkers to do with the kidneys in pregnancy

Answer 24

• Renal tubules reabsorptive capacity for ions is increased due to increased production of steroid hormones by placenta and adrenal cortex.
• Decreased plasma urea, creatinine and uric acid. Uric acid rises before creatinine in response renal impairement

Question 25

What are some gastrointestinal tract changes?

Answer 25

• Constipation due to uterus pressing on colon and rectum, Relaxation of SM by placental progesterone which reduced gut motility and there is a reduction in water content.
• Gastric acid reflux due to relaxation of lower oesophageal sphincter, relaxation of GI smooth muscle and pressure of uterus