ICL 15.14: Maternal Adaptations to Pregnancy

Question 1

what are the common non-pathological problems women complain of during pregnancy?

Answer 1

1. anemia
2. morning sickness
3. bachache
4. increased need to urinate
5. pins and needles
6. leg cramps
7. hemorrhoids and constipation
8. varicose veins
9. stolen ankles

Question 2

what causes pins and needles during pregnancy?

Answer 2

carpal tunnel

Question 3

why do pregnant women become anemic?

Answer 3

plasma volume is increased by 50%!!!! it peaks at 24 weeks

there’s parallel increase in RBCs and blood volume BUT the RBCs dont increase as much as the plasma so there is a functional dilution resulting in anemia

Question 4

how is there increased blood volume during pregnancy? where does the volume come from?

Answer 4

increased water retention of 6.5 to 8 L for the fetus, placenta, AF, blood volume, and RBCs

this increased volume happens due to:
1. increased sodium reabsorption via increased aldosterone levels that cause increase in tubular reabsorption that exceeds the amount of sodium filtration

2. osmotic threshold is reset for ADH secretion –> ADH secretion isn’t stimulated at the normal level, it is reset so that it responds to a lower plasma osmolality than it usually would

posterior pituitary responds to a lower plasma osmolality and increases water retention! this allows for maternal blood volume to expand

Question 5

why is increased blood volume important for the mother postpartum?

Answer 5

during delivery, there is a lot of maternal hemorrhage so this helps protect the mother against all the blood loss

this prevents hypovolemia and hemorrhagic shock from occurring during delivery

Question 6

how does the heart handle the increased blood volume during pregnancy?

Answer 6

increased SV and HR and CO

CO = HR x SV

HR increases 15-20 beats to accommodate a new blood volume of 7.4 L/minute!! BUT it is NEVER above 100 and if it is then you should be worried maybe they have a PE causing tachycardia

Question 7

what changes occur in the vasculature to accommodate the increase in blood volume?

Answer 7

BP decreases until 22-24 weeks and returns to baseline at 36 weeks

this is due to progesterone causing smooth muscle relaxation which decreases systemic vascular resistance to allow for accommodation of increased blood volume

Question 8

how does colloid oncotic pressure change during pregnancy?

Answer 8

it decreases

this is because albumin is the main contributor of COP and during pregnancy albumin concentrations are diluted due to increase of blood volume

Question 9

what is the clinical significant of the cardiovascular changes?

Answer 9

1. flow murmur due to increased blood volume causing S3
2. ankle edema due to reduction of colloid oncotic pressure so fluid leaves into the tissues or even the lungs…(potential pulmonary edema….)
3. LV hypertrophy
4. physiological anemia with Hct of 32-36%

Question 10

how do you differentiate between pathological anemia vs. pregnancy anemia?

Answer 10

RDW and MCV

MCV shouldn’t change in pregnancy

look at ferritin and TIBC –> TIBC usually increases in pregnancy

Question 11

34 year old
primigravida at 28 weeks c/o anemia.
Patient is concerned because she saw her CBC result.
Her hematocrit was 32%.

is she anemia?
what additional info do you need to ermine etiology?

what happens to TIBC in a normal pregnancy?

Answer 11

yeah she’s anemic but it’s due to pregnancy

TIBC will increase due to decrease in albumin

Question 12

what happens to the coagulation system in pregnancy?

Answer 12

clotting is increased in pregnancy – fibrinogen levels double in pregnancy!!

specifically, factors 7, 8, 9, 10 and vWF all increase during pregnancy

this is because estrogen:

1. promotes blood clotting which increases levels of fibrinogen and activity of coagulation factors
2. decreases the activity of antithrombin II which increases the risk of venous thromboembolism, PE, DVT (most common causes of maternal morbidity and mortality!)

Question 13

how would you diagnose a pregnant woman for tachycardia?

Answer 13

1. EKG to look for RV hypertrophy – strain on the RC would indicate clogging of the pulmonary artery/in the lungs
2. RR
3. O2 saturation
4. ABG

D-dimer not useful in pregnancy because they’re just baseline elevated due to baseline inflammation during pregnancy

Question 14

how does the increased blood volume impact the urinary system?

Answer 14

kidneys increase in size; right one more than the left

ureters may be slightly enlarged; right more than the left –> this is because the uterus compresses ureters at the pelvic brim and progesterone causes ureteral relaxation!

bladder capacity does NOT change

increased urinary frequency is common

Question 15

your pregnant patient calls your office. she is urinating more frequently than
usual. how do you respond?

Answer 15

does she have other symptoms?

if she says she’s burning or there’s hematuria get a urine cultured

if her culture shows e. coli give antibiotics! so UTIs get treated the same in pregnancy – the only thing that’s different is that we treat asymptomatic bacteruria to prevent pyelonephritis and stones that pregnant women are already prone for during pregnancy due to the changes in the urinary system like dilated ureters or compressed ureters –> untreated bacteruria is a risk factor for maternal UTIs and preterm contracts and preterm labor

Question 16

how does the rib cage change during pregnancy?

Answer 16

increase in subcostal angle, transverse diameter and circumference chest

with advanced gestation diaphragm is pushed up and lung volume will decrease overall!!

Question 17

how do lung capacities change with pregnancy?

Answer 17

1. total lung capacity decreases
2. increase in tidal volume (30-40%)
3. expiratory reserve volume and residual volume decrease

Question 18

why does tidal volume change during pregnancy?

Answer 18

TV increases during pregnancy

progesterone mediates these changes!!

overall, respiratory rate is unchanged during pregnancy but tidal volume increases due to progesterone by changing medulla sensitivity to PCO2

progesterone stimulated medulla so that women take deeper breaths and there’s increased ventilation which increases alveolar oxygen and subsequently decreases alveolar CO2 – as a result there’s decreased arterial PCO2 which results in excretion of bicarbonate by the kidney to compensate which ultimately results in chronic respiratory alkalosis!!!

minute ventilation = TV x RR

Question 19

how does an ABG change for a pregnant woman?

Answer 19

PaO2 increases

PaCO2 decreases – this is because the baby needs to get rid of its CO2 so for it to diffuse down its gradient, the maternal CO2 needs to be lower so the CO2 can diffuse out of the placenta!

unfortunately dyspnea is common complaint due to increased CO2 but tachypnea on the other hand isn’t normal!

Question 20

how is the GI tract effected during pregnancy?

Answer 20

progesterone slows the GI tract down

unusual cravings, blunted sense of taste

morning sickness = hyperemesis

hyperemesis gravidarum = hyperemesis with weight loss and electrolyte changes

reflux/heart burn

hemorrhoids and constipation are common too because rectal vein is being super perfusing during pregnancy!

Question 21

what happens to the cervix through pregnancy?

Answer 21

softens due to change in composition since it has to dilate for birth

Question 22

how much does CO to uterus change?

Answer 22

.1% to 10% during pregnancy!!

that
s 750 mL/minute!!!

this is why after delivery it’s so important to prevent excessive bleeding and usually that’s done by smooth muscle traction – the most common cause of uterine bleeding is uterine atony