Repro: Maternal adaptations to pregnancy

Question 1

What tests are done in antenatal screening?

Answer 1

• assess risk factors for gestational diabetes
• blood group for rhesus incompatibility (postive mother and negative fetus etc)
• Hb to check for anaemia
• look for teratogenic infections eg HIV, syphillis, rubella
• check for proteinuria, signs of pre-eclampsia are proteinuria and hypertension

Question 2

How to the cardiovascular system change during pregnancy?

Answer 2

Blood volume increases by 50% because there is a new special circulation to support, also anticipatory for 0.5-1L of blood loss during labour.

CO and HR and SV all increase
Systemic vascular resistance decreases due to high conc of progesterone relaxing the smooth muscle

Question 3

How does blood pressure change during pregnancy?

Answer 3

T1 and T2: progesterone decreases systemic vascular resistance so hypotension is normal
T3: the aorta and IVC is compresses by gravid uterus so BP returns back to normal

NB: a normal BP in T1 and T2 si actually hypertension which is a sign of pre-eclampsia

Question 4

What is pre-eclampsia? What are the signs?

Answer 4

Pre-eclampsia is the precursor to eclampsia which is fits during pregnancy (emergency)
Signs are hypertension (to compensate for unsufficient placental support) and proteinuria.

Question 5

How does the urinary system change during pregnancy?

Answer 5

GFR increases (secondary to effects of progesterone) leading to a decrease in functional renal reserve.
Increased GFR means there is increases creatinine clearance, therefore a normal creatinine level is suspicious)
Renal plasma flow increases

Question 6

Why are UTIs really common in pregnancy?

Answer 6

Progesterone relaxes the ureter and the gravid uterus obstructs flow = urinary stasis
Urine is dipped at every visit

Question 7

How does the respiratory system change during labour?

Answer 7

The diaphragm is upwardly displaced therefore there is decreased functional residual capacity but vital capacity and total lung volume is unchanged due to increase in chest circumference.
Physiological hyperventilation: due to increased Co2 productions, progesterone works on resp centre in brain to blow off extra CO2. This is compensated by increased renal bicarb excretion

Question 8

How is carbohydrate metabolism changed during pregnancy?

Answer 8

There is placental transport of glucose via facilitated diffusion.
Pregnancy increases maternal insulin resistance (switches to gluconeogenesis and fatty acids) which is achieved by human placental lactogen

Question 9

What are the risk factors for gestational diabetes?

Answer 9

• Prediabetes
• High blood pressure
• A history of gestational diabetes
• A family history of type 2 diabetes
• Hormone disorders, such as polycystic ovary syndrome (PCOS)
• Being overweight, or gaining too much weight during pregnancy
• Being older than 25
• Being of African, American Indian, Asian, Hispanic, or Pacific Islander descent
• Previously giving birth to a baby that weighed at least 9 pounds or had a birth defect
• Previously having an unexplained stillbirth or miscarriage

Question 10

Whats risks are associated with poor control of gestational diabetes?

Answer 10

• macrosomic fetus (can cause problems with delivery)
• increased risk of stillbirth
• increased risk of congenital defects

Question 11

How does lipid metabolism change during pregnancy?

Answer 11

Increased lipolysis from T2 in order to increase fatty acids on fasting (dont cross placenta so preserve energy supply for mother)

Question 12

Why is there an increased risk of ketoacidosis during pregnancy?

Answer 12

• pregnancy is a state of insulin resistance, therefore the insulin requirement is raised
• there is accelerated starvation due to high energy demands of the fetus, therefore the insulin deficiency increased fatty acids which convert to ketones
• nausea and vomiting are common which increase anti insulin hormones
• there is less buffering capacity due to the respiratory alkalosis increasing renal bicarb excretion

Question 13

How does thyroid function change during pregnancy?

Answer 13

TBG, T3, T4 all increase but free T4 stays within the normal range
hCG has a direct effect on TSH (can be decreased in normal pregnancies)

Question 14

How to the GI system change during pregnancy?

Answer 14

• progesterone relaxes the smooth muscle
• there is delayed emptying of GI tract
• increased risk of pancreatitis due to hyperlipidaemia

Question 15

Why is anaemia common in pregnancy?

Answer 15

Plasma volume increases ~50%, the red cell mass also increases but not as much ~25%. Therefore there is a dilution effect.
Anaemia due to Fe and folate deficiency can occur due to fetal demands for iron

Question 16

How does the immune system change during pregnancy?

Answer 16

The fetus is an allograft (genetically distinct from the mother) therefore there is suppression of the immune system at the maternofetal interface. Therefore increased risk of infections.