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OB- Overview > Exam 2 Fetal Stuff > Flashcards

Exam 2 Fetal Stuff Flashcards

1
Q

Blood supply to the placenta is mainly from

A

Uterine arteries

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2
Q

The uterine artery arises bilaterally from the

A

internal iliac arteries

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3
Q

In pregnancy, flow my differ between the R+L uterine arteries- explain

A

The vessel that supplies the placental side will have 18% increase in blood flow and 11% increase in diameter

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4
Q

How much is the uterine blood flow in the non-preg

A

50-100ml/min

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5
Q

How much is the uterine blood flow at term?

A

700-900ml/min

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6
Q

At term, how much uterine blood flow perfuses the placenta and how much perfuses the myometrium?

A

80% perfuses placenta

20% perfuses the myometrium

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7
Q

Maximal dilation of uterine vessels during pregnancy- So what is absent?

A

autoregulation is absent

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8
Q

Extreme hypocapnia does what to the uteroplacental blood flow?

A

Extreme hypocapnia (PaCo2<20mmHg) causes decreased UBF causing fetal hypoxemia and acidosis

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9
Q

UBF is directly proportional to

A

Uterine perfusion pressure (which is the difference between uterine arterial pressure and uterine venous pressure)

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10
Q

How do you calculate uterine perfusion pressure?

A

U arterial pressure - U venous pressure

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11
Q

Uterine perfusion pressure is directly proportional to

A

Uterine blood flow

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12
Q

UBF is inversely proportional to

A

Uterine Vascular resistance

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13
Q

Uterine Vascular resistance is inversely proportional to

A

UBF

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14
Q

How do you calculate UBF?

A

Uterine perfusion pressure/Uterine Vascular resistance

Or in other words UBF= UAP-UVP/UVR

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15
Q

What are the 3 major factors that decrease UBF?

A 
Hypotension (decreases uterine perfusion pressure)
Uterine vasoconstriction (Increases UVR)
Uterine contraction (Dec UPP and Inc UVR)
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16
Q

What happens to uterine perfusion during contractions?

A

Decreases

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17
Q

What happens to uterine perfusion during uterine relaxation

A

Increases

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18
Q

What some things that can cause Decreased uterine arterial pressure?

A

Supine position (aortocaval compression)
Hemorrhage/hypovolemia
Drug-induced hypotension
Hypotension during sympathetic blockade

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19
Q

What are some things that can cause Increased uterine Venous pressure?

A

Vena caval compression
Uterine contractions
Drug induced uterine tachysystole (oxytocin, LA)
Skeletal muscle hypertonus (Scz, Valsalva)

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20
Q

What can cause Increased Uterine Vascular Resistance?

A

Endogenous vasoconstrictors - Catecholamines, Vasopressin

Exogenous Vasoconstrictors- Epi, Neo, ephedrine, LA

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21
Q

NA will cause (increased/decreased) uterine blood flow?

A

Both

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22
Q

How does NA increase UBF?

A

Increase by:
Pain relieve
Decreased sympathetic activity
Decreased maternal hyperventilation

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23
Q

How does NA decreased UBF?

A

Hypotension
Unintentional IV injection of LA or epi
Absorbed local anesthetic (little effect)

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24
Q

How do inhalational agents affect UBF?

A

0.5-1.5 MAC has little to no effect on UBF

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25
Q

How does ventilation effect UBF?

A

Moderate hypoxemia and hypercapnia have little effect

However Alkalosis will decrease UBF. So AVOID HYPERVENTILATION .

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26
Q

The maternal side of the placenta is called the

A

Basal plate or Dicidua Basilus

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27
Q

The fetal side of the placenta is called the

A

Chorion or Chorionic plate

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28
Q

What lies between the Basal plate and the Chorionic Plate?

A

Intervillous space

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29
Q

How much blood can be held in the intervillous space?

A

350ml

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30
Q

Where does O2/Nutrient Exchange occur in the placenta?

A

Terminal Arterioles/terminal villi

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31
Q

How much is UBF at term? Which is what % CO?

A

UBF at term
Max 700-900ml
Which is 10% of maternal CO

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32
Q

How much blood supplies the myometrium and Decidua?

A

Myometrium 150ml/min

Decidua 100ml/min

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33
Q

How much of the UBF supplies the intervillous space

A

80% of UBF supplies the intervillous space

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34
Q

Describe the maternal blood flow in regards to regulation of placental blood flow.

A

Spiral arteries can vasodilate as much as 10x normal diameter
Maternal blood flow enters at pressure of 70-80mmHg and rapidly decreases to 10mmHg

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35
Q

Describe the Fetal blood flow in regards to placental blood flow regulation

A

Fetal BF is controlled via effects of adrenomedullin (helps maintain placental vessel tone)
net efflux/influx of water is regulated by fetal blood pressure (fetal BP causes increase/decrease water across placenta)
Local autoregulator effects- Relaxin factors (prostacyclin and nitric acid) help control placental / Fetal circulation

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36
Q

Passive transport depends on

A 
Concentration of electrochemical difference
Molecular weight
Lipid solubility
Degree of ionization
Membrane surface area and thickness
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37
Q

Facilitated transport depends on

A

Saturation kinetics
Competitive and noncompetitive inhibition
Sereospecificity
Temperature influences (inc temp=inc transfer)

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38
Q

With passive transport, the rate of diffusion is proportional to

A

the difference in the concentration gradient

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39
Q

Describe PO2 and PCO2 changes as blood moves from mother to placenta to fetus to placenta to mother

A

PO2/PCO2 Mother to placenta 98/28, Placenta to fetus (umbilical vein) 28/35, Fetus-to placenta (umbilical artery) 15/44, placenta to mother 33/37.

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40
Q

The placenta provides ___ ml O2/min/kg fetal body weight.

A

The placenta provides 8ml of o2/min/kg of fetal body weight

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41
Q

The placenta has ____ the O2 transfer efficiency of the adult lung

A

1/5

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42
Q

Factors that effect the transfer of respiratory gasses and nutrients from placenta to fetus

A

Ratio of maternal to fetal placental blood flow
O2 partial pressure gradient between the 2 circulations
Diffusion capacity of the placenta
Maternal and fetal Hgb capacities
O2 affinities
Acid/Base balance of fetal/maternal blod

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43
Q

How does glucose cross the placenta

A

simple diffusion and stereospecific-facilitated diffusion

44
Q

How does insulin cross the placenta

A

It doesn’t

45
Q

List the factors affecting drug transfer across the placenta

A 
Lipid solubility
Protein binding
Tissue binding
pKa
pH
Blood flow
46
Q

How does molecular weight affect placental transfer

A

<1000 will cross (ex morphine) >1000 will not transer

47
Q

How does charge of molecule affect placental transfer

A

Uncharged will cross, Charged will not transfer

48
Q

How does lipid solubility affect placental transfer

A

Lipophilic agents cross, hydrophilic agents will not transfer

49
Q

How to pH versus drug pKa affect placental transfer

A

Higher proportion of UNionized drug in maternal plasma will transfer, higher proportion of Ionized drug in maternal plasma will not cross

50
Q

3 factors minimizing drug effects on the fetus

A

Dilution (drug diluted before reaching fetal circulation)
Fetal CO (shunted blood does not circulate)
Acid / Base status of fetus (“ion trapping”)

51
Q

What drug do NOT cross the placenta

A

Glycopyrollate
Heparin
NMB-both types
Neo (Phenylephrine)

52
Q

What drugs Do cross the placenta

A

Pretty much everything other than Glyco, Heparin, NMBs, and Neo.

53
Q

How many mls of amniotic fluid at term?

A

400ml Between 10-20 weeks, vol increases from 25ml-400ml

54
Q

Amniotic fluid consists of

A

Fetal urine and respiratory secretions

55
Q

In fetal tissues, hypoxia occurs at O2 tension of

A

<17mmHg

56
Q

What is the normal O2 tension of the fetus

A

20-25mmHg. SO if hypoxia occurs at 17mmHg, there is a very small margin of safety.
*Remember PO2/PaCo2 from the flow diagram was 28/35 (Placenta to Fetus)

57
Q

In fetal tissues, hypoxia can occur at what O2 tension?

A

17mmHg or less…small margin of safety

58
Q

Does the fetus have a good oxygen reserve?

A

Nope

59
Q

What % of O2 from blood flow to the uterus is used for placental processes?

A

40% The Placenta is a “conduit and consumer” of O2

60
Q

What is the normal range for glucose in the fetal circulation? How does obtain this?

A

54-90mg/dl The only glucose available for the fetus is what transfers across the placenta

61
Q

The fetus produces ____x as much heat and maintains a temp of _____ greater than the mother

A

2x, 0.5 degrees Cel, > the mother

62
Q

Due to high fetal metabolic rate, net flow of heat is from _____ to ______.

A

Fetus to mother

63
Q

Fetus generates heat via (Metabolic activity or thermogenic mechanisms)?

A

Metabolic activity. (nonshivering thermogenesis occurs due to mitochondria, fat vacuoles, sympathetic innervation and blood vessels).
The ability to generate heat via thermogenic mechanisms isn’t developed until the end of gestation.

64
Q

What is the normal length of the fetus as 12wks, 20wks, 40wks?

A

12w=10cm, 20w=25cm, 40wk=53cm

65
Q

Wt at 23wks, 7mos, 8mos, and birth

A

23weeks=1lb
7mos=3lb
8mos=4lb
birth=7lb

66
Q

How long after fertilization do gross characteristics of all organs begin to develop?

A

1 month

67
Q

How long until details are developed in the organs?

A

2-3months

68
Q

When are the organs grossly the same as the neonate?

A

4 months

69
Q

The fetal circulation receives the CO from the (R or L ventricle)

A

BOTH- “Ventricles work in parallel”

70
Q

What connects the umbilical vein to the IVC

A

Ductus Venosus

71
Q

What connects the RA to LA?

A

Foramen Ovale

72
Q

What connects the PA to the Descending Aorta?

A

Ductus Arteriosus

73
Q

What structures does blood flow through as it leaves the placenta headed to the fetus…in order starting with Umbilical Vein

A 
Umbilical Vein
Ductus Venosus 
IVC
RA
LA
LV 
Brain 
SVC
RV
PA
Ductus Arteriosus
Descending Aorta
Lower extremities
Hypogastric arteries
Umbilical Artery
Placenta
74
Q

What is the normal Fetal Intravascular Volume?

A

110ml/kg

75
Q

What % of the fetal blood volume is in the placenta?

A

25% (80ml/kg is in the fetus, 110ml/kg total)

76
Q

The Blood volume in the FETAL BODY is about____ ml/kg

A

80ml/kg Remember 110ml/kg total (fetus and placenta) 25% is in the placenta, 80ml/kg is in the actual fetus. She is gonna F this right up on the exam.

77
Q

The Combined Ventricular Output (CVO) is what at mid gestation and what at term?

A

210ml at mid gestation. Increases to 1900ml at 38weeks (500ml/kg)

78
Q

Fetal hearts begins beating at _____ weeks at ___bpm

A

4th week, 65bpm

79
Q

HR steadily _____ until reaches around ____bmp

A

HR increases up to around 140bpm

80
Q

True alveoli develop at ____weeks

A

36weeks

81
Q

When does the majority of alveoli develop?

A

6-18 months of life

82
Q

What causes the Reduction in PVR at birth–Pick 4!

A

Expulsion of lung liquid
Abrupt surge in pulmonary blood flow
Creation of alveolar surface tension
Predominance of vasodilators vs vasoconstrictors

83
Q

Surfactant is composed of mostly-

A

Lipids (90%) with the remainder being proteins

84
Q

Where is surfactant produced?

A

Surfactant is formed in the Endoplasmic Reticulum and Golgi Apparatus in Type 2 alveolar cells

85
Q

At 20 weeks, 90% of the amniotic fluid is provided by what organ?

A

Fetal Kidneys

86
Q

Has 2 alpha chains and 2 gamma chains

A

Hgb F

87
Q

What is the Tetramer for Hbg A?

A

2 alpha chains and 2 beta chains

88
Q

Hbg F has a greater affinity for ____ and a lower affinity for _____

A

greater affinity for oxygen,

lower affinity for 2-3 DPG

89
Q

The p50 in the adult is____, while the p50 in the fetus is _____.

A

Adult p50=27

Fetal p50=19

90
Q

The fetal oxyhgb saturation curve is shifted to the _____ compared to the mother.

A

Left

91
Q

Meconium stained amniotic fluid means either

A

decreased clearance or increased passage (stress or infection)

92
Q

What are the 3 potential detrimental effects of meconium stained amniotic fluid?

A
  1. Umbilical cord vessel constriction, vessel necrosis, and production of thrombi.
  2. Decreased antibacterial properties of amniotic fluid by altering zinc levels
  3. Fetal aspiration-neutralizes action of surfactant, promotes lung tissue inflammation through activation of neutrophils, possibly result in meconium aspiration syndrome
93
Q

What are the 4 compensatory responses of the healthy fetus to uterine contractions?

A
  1. Decreased O2 consumption
  2. Vasoconstriction of nonessential vascular beds
  3. Redistribution of blood flow to vital organs
  4. Humoral responses to enhance fetal cardiac function during hypoxia (release of epi, vasopressin, endogenous opioids).
94
Q

What are abrupt changes in FHR above baseline?

A

Accelerations (Past 35wks, peak of at least 15bmp above baseline, lasting >15 sec).

  • Prolonged lasts for at least 2 min
  • > 10 min = new baseline
95
Q

Which deceleration occurs with each uterine contraction with <20bpm below baseline?

A

Early- thought to be result of vagal reflex to mild hypoxia, not ominous.

96
Q

Late Decelerations -

A

Begin 10-30 seconds AFTER beginning of uterine contraction and end 10-30 sec after end of uterine contraction

97
Q

Define FHR variability

A

Fluctuation in FHR of 2 cycles or greater per min

*normal- reflects presence of normal intact pathways

98
Q

Diff Dx with decreased FHR variability:

A

hypoxia, sleep state, neurologic abnormalities, decreased CNS from drug exposure (opioids)

99
Q

What is Ominous with FHR variabilities

A

Late decelerations and decreased or absent variability is ominous.

100
Q

What is the normal FHR?

A

Normal is 110-160bpm- determined by assessing mean HR over 10 min.

101
Q

What type of deceleration varies in depth, shape and duration and is usually d/t umbilical cord compression?

A

Variable- she also says during 2nd stage of labor, can be d/t compression on fetal head.

102
Q

What type of pattern appears regular, smooth, wavelike and may signal fetal anemia; effect of maternal opioid

A

Sinusoidal (looks like v tach)

103
Q

What type of pattern is excessive alteration in variability (>25bpm) and may signal acute fetal hypoxia

A

Saltatory (looks like v fib)

104
Q

ACOG recommendations for FHR monitoring how often

A 
HIGH RISK
Q 15 min during 1st stage of labor
Q5 min during 2nd stage
LOW RISK
Q 30m 1st stage
Q 15m 2nd stage
105
Q

Discuss the ACOG 3 tier system to categorize FHR patterns

A 
CAT 1 (normal) strongly predictive of normal fetal acid/base status at the time of observation
CAT 2 (indeterminate) not predictive of abnormal fetal acid/base status, but without adequate evidence to classify as normal or abnormal
CAT 3 (abnormal) predictive of abnormal fetal acid/base status at the time of observation and requires prompt evaluation.
106
Q

CAT 3 tracings include:

A 
Absent baseline FHR variability and any of the following:
Recurrent late decelerations
Recurrent variable decelerations
Bradycardia
Sinusoidal pattern
107
Q

CAT 1 tracings include

A 
Baseline HR 110-160bpm
Baseline FHR variability: moderate
Accelerations: present of absent
Late or variable decelerations: ABSENT
Early Decelerations: present of absent

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