Lecture 1: Cardiovascular & Renal Adaptations in Pregnancy

Question 1

What are adaptations required for in pregnancy?

Answer 1

Increase CO and BV - maintain uteroplacental perfusion and maintain metal demands

Question 2

How long is human pregnancy (from last menstrual period and fertilisation)?

Answer 2

280 days (40 weeks)

266 days (38 weeks)

Question 3

What are the physiologic adaptations to pregnancy?

Answer 3

Hyperdynamic, hypermetabolic, hypervolemic, hypercoaguable, low resistance, compensatory respiratory alkalemia, diabetogenic

Question 4

What is the ideal weight gain in pregnancy and when does it occur?

Answer 4

10-13kg, with 1-2kg in first trimester and 1-2kg/month in the 2nd and 3rd trimesters

Question 5

Why is there extensive cardiac and resp work during pregnancy?

Answer 5

Additional breast tissue and uterine muscle are major contributors of increase in cardiac and resp work

Question 6

What is the importance of glucose in pregnancy?

Answer 6

Major energy source for fetal and placental growth

Question 7

When does maternal hyperglycaemia occur?

Answer 7

Late gestation

Question 8

Why is there increased insulin synthesis and secretion?

Answer 8

Increased beta cell division and size

Question 9

How much blood is lost in delivery?

Answer 9

500-600mL vaginal

800-1200mL caeserean

Question 10

When should blood volume increase?

Answer 10

During pregnancy to accommodate for later loss of blood

Question 11

What is the % increase of BV and when does it occur?

Answer 11

30-50% - begins at 6 weeks and peaks at 32 weeks

Question 12

What is the % increase in plasma volume?

Answer 12

40-50%

Question 13

What is the % increase in red cells mass and when does it occur?

Answer 13

25-30% – begins at 10 weeks and continues until term

Question 14

Why does red cell mass increase?

Answer 14

Increased erythropoietin and red blood cell production

Question 15

Why doe physiological anaemia and hemodilution occur?

Answer 15

Increase in blood volume exceeds increase in red blood cells

Question 16

What is the % increase of white blood cells ad when does it occur?

Answer 16

25-30% - increase in 1st trimester and plateau in 2nd and 3rd

Question 17

How does the number of total plasma proteins change?

Answer 17

Reduced albumin due to increased blood volume– 1st trimester – changes made contribute to propensity of oedema

Question 18

What is the % increase of total serum lipids?

Answer 18

40-60%

Question 19

What is the % of increase in cholesterol and why is this important?

Answer 19

40% - it is an important precursor for oestrogen and progesterone

Question 20

What are the changes in CV functioning?

Answer 20

Increased CO by 30-50%

• Increased SV from 8 weeks
• Increased HR from 5 weeks
• Increased fluid retention/oedema

Question 21

What are the changes to BP in pregnancy and when do they occur?

Answer 21

Reduced BP – lowers in 1st trimester and is lowest at 24-32 weeks and returns to normal by term

Question 22

Is systolic or diastolic BP lower and why?

Answer 22

Diastolic pressure reduced more than systolic due to progesterone and relaxin reducing vascular resistance, blood being directed to placenta and refractory (protective) increases in renin and Ang II

Question 23

What happens to volume sensors in the kidney during pregnancy?

Answer 23

Reset

Question 24

What is the % increase of renal blood flow in pregnancy?

Answer 24

40-80%

Question 25

What is the increase in GFR in pregnancy?

Answer 25

30-50%

Question 26

How does kidney size change during pregnancy?

Answer 26

Increase by 1m due to increased renal blood flow and glomerular hypertrophy

Question 27

What does increased renal blood flow and GFR result in?

Answer 27

Increased filtration of water and solutes – increased urine flow and volume. However, renal tubules retain sodium and water to maintain blood/plasma volume expansion

Question 28

What does blood volume increase to?

Answer 28

7L

Question 29

When is plasma osmolality reduced?

Answer 29

By week 5 of pregnancy - 10mosmol/kg lower than preconception values by week 10

Question 30

How does the fluid relate to the foetus function in utero?

Answer 30

Foetus surrounded by fluid - not breathing oxygen, receiving it from mother via placenta. Foetus urinates in utero but don’t want to release toxins into fluid that baby swallows - placenta and mother act as foetal kidneys to filter toxins from womb as kidneys develop. Fluid develops GIT but has no nutritional value - placenta provides nutrition from mother. If these adaptations don’t happen adequately and alter placental function these actions will be compromised

Question 31

How is oxygen delivered to the baby?

Answer 31

Umbilical vein takes oxygenated blood to baby and umbilical arteries take deoxygenated blood away

Question 32

How does the placenta avoid problems with vasoconstriction?

Answer 32

Blood lakes

Question 33

What is the blood flow to the lungs in utero?

Answer 33

Less than 10%

Question 34

Where is oxygen saturation lowest and highest in the foetus?

Answer 34

Abdominal IVC and umbilical vein

Question 35

Does the foetus have high or low PO2 and haemoglobin levels?

Answer 35

Low PO2 and high haemoglobin

Question 36

Why is oxygen consumption higher in foetus?

Answer 36

Lower oxygen saturation but higher oxygen delivery and flow

Question 37

What are the four shunts for blood in the foetus?

Answer 37

- Ductus Venosus: abdominal umbilical vein to IVC, streamlines blood flow to atria - Foramen Ovale: right atrium to left atrium - Dutus Arteriosus: Right ventricle, pulmonary artery to descending aorta, avoid blood perfusion to lungs - Umbilical circulation – 1 vein brings oxygenation blood from placenta to fetus and 2 arteries remove deoxygenated blood

Question 38

Why does ductus vernosus close?

Answer 38

Not being used or demanded (probably flow mediated) – closed 1-3 weeks after birth and later in premature babies (trigger unknown)

Question 39

Why does foramen ovale close?

Answer 39

Pressure change due to airflow when breathing

Question 40

Why does ductus arteriosus close?

Answer 40

Closes two days after birth due to oxygen mediated inhibition