Uteroplacental & Fetal Physiology Pt. 2 (Exam II) Flashcards
1
Q
What is MVU?
A
Montevideo Units
2
Q
What is TOCO?
A
Tocodynamometer
3
Q
What is IUPC?
A
Intrauterine Pressure Catheter
4
Q
What is FSE?
A
Fetal Scalp Electrode
5
Q
What is CPD?
A
Cephalopelvic Disproportion
6
Q
What is BPP?
A
Biophysical Profile
7
Q
What is DA?
A
Ductus Arteriosus
8
Q
What is DV?
A
Ductus Venosus
9
Q
What is FO?
A
Foramen Ovale
10
Q
What is HbF?
A
Fetal Hemoglobin
11
Q
What is HbA?
A
Adult Hemoglobin
12
Q
What is FHR?
A
Fetal Heart Rate
13
Q
Fetal circulation is ______ in contrast to adult circulation which is _____ _____.
A
parallel : in series
14
Q
What are the three anatomic communication of fetal circulation?
A
- Ductus Venosus
- Foramen Ovale
- Ductus Arteriosus
15
Q
Pulmonary vascular resistance is ____ in fetus. Why is this?
A
High
- Fetal lungs are collapsed & filled with fluid.
- Little pulmonary circulation = gas exchange happening in the placenta
16
Q
Systemic Vascular Resistance is _____ in the fetus. Why?
A
Low
- Placenta has a low resistance vascular bed.
17
Q
The umbilical ____ brings oxygenated blood from the placenta to the fetus.
A
umbilical vein.
18
Q
The umbilical _____ send deoxygenated blood form the fetus back to the placenta.
A
umbilical arteries (2).
19
Q
In fetal circulation both the ____ & ____ sides of the heart provide ________ blood flow to the fetus.
A
- right and left
- systemic blood flow
20
Q
Fetal Circulation
What is the Ductus Venosus?
A
- blood vessel that allows oxygenated blood from placenta to bypass immature portal circulation - goes straight to the IVC
21
Q
Fetal Circulation
What is the Foramen Ovale?
A
Opening that directs oxygenated blood from the RA to LA
bypasses immature fetal lungs
22
Q
Fetal Circulation
What is the Ductus Arteriosus?
A
Blood vessel that connects the pulmonary artery to the descending aorta
* diverts blood flow away from underdeveloped lungs
23
Q
What is the PO₂ of maternal blood in the placenta?
What is the (typical) O₂ saturation of the maternal blood?
A
PO₂ = 30-35 mmHg
SaO₂ = 80-85%
24
Q
How does the fetus maintain adequate oxygenation when exposed to a “low” O₂ saturation?
A
HbF will preferentially pull O₂ from the mom’s HbA due to its higher affinity.
25
What are the cardiac output contributions of the right ventricle and left ventricle of the fetus?
RV = 67% of CO
LV = 33% of CO
Parallel circulation (not in-series like adults).
26
Which fetal vessel allows oxygenated blood from the placenta to bypass portal circulation and go straight to the inferior vena cava?
Ductus Venosus
27
What aspect of fetal circulation allows oxygenated blood to flow from the RA to the LA?
What does this bypass?
Foramen Ovale (FO)
- Allows bypass of immature fetal lungs.
28
What causes the high right-to-left shunt of the foramen ovale?
Due to pressure gradient from **high fetal PVR**.
29
What vessel diverts blood away from underdeveloped lungs?
Ductus Arteriosus
## Footnote
*connects the pulmonary artery to the descending aorta*
30
What fetal blood vessel connects the pulmonary artery and the descending aorta?
Ductus Arteriosus
31
What vessel carries oxygenated blood from the placenta to the fetus?
Umbilical Vein (80-85% saturated)
32
Where does blood from the umbilical vein go?
- 50% to fetal portal circulation
- 50% bypasses portal circulation through DV to IVC.
33
The percentage of umbilical vein blood directed to the liver will increase in conjunction with ______ ____.
gestational age
34
Does **all** blood from the RA bypass the lungs and go directly into the left atrium via the FO?
No. Some blood from the RA will go to the RV and then immature pulmonary circulation.
35
Describe the path for most of the blood through fetal circulation.
RA → FO → LA → LV → Aorta → systemic circulation.
36
What percentage of blood goes from the RA to the RV and subsequently perfuses the lungs?
10%
37
What is greater in a fetus, PVR or SVR?
PVR
38
The majority of fetal blood passes from the pulmonary artery through the ____ to the descending aorta to perfuse the lower body of the fetus.
DA (Ductus Arteriosus)
39
Where do the umbilical arteries originate?
Lower vena cava
40
What does the DV do?
Shunts blood from the liver to the heart
41
What does the DA do?
Shunts blood from pulmonary circulation to the ascending aorta.
42
What portion of the autonomic nervous system develops first and is predominant throughout fetal life?
Parasympathetic system
43
What are the main environmental factors affecting fetal baroreceptors and thus SNS output?
Maternal BP & stress
44
When does respiratory effort begin after delivery?
30 - 90 seconds typically
45
What respiratory changes occur at birth?
- ↓ Intrathoracic pressure = Air enters lungs
- Lung expansion = ↑ PaO₂ ↓ PaCO₂
- ↑ pH & alveolar O2 tension **↓PVR**
## Footnote
**going from high PVR to low PVR**
46
What does the decreased PVR upon birth do to pulmonary blood flow?
↑ pulmonary artery flow = RV output shifts to lungs = ↑ pulmonary blood flow
47
What does surfactant do?
↓ surface tension = prevention of alveolar collapse
48
When does surfactant production start?
24 - 28 weeks gestation
## Footnote
*steroid administration to help produce surfactant*
49
The ____ will constrict and close due to increased O₂ levels.
DA
## Footnote
*right after baby is born*
50
Why does the foramen ovale close?
Closes due to LA pressure exceeding RA pressure
51
What causes LA pressure to exceed RA pressure in a neonate?
Clamping of the umbilical cord = ↑SVR = ↑LAP = ↓ right-to-left sunt
52
This vessel closes with the clamping of the umbilical cord due to an increase in IVC pressure.
Ductus Venosus (DV)
53
What four factors can cause PVR to remain elevated after delivery?
- Hypoxia
- Acidosis
- Hypovolemia
- Hypothermia
54
What drug class when used by a mom can cause premature constriction of the ductus arteriosus and thus persistent pulmonary hypertension of the newborn?
NSAIDs
55
What things can lead to premature constriction of the DA?
- NSAIDs
- Preterm births
- ↑ PA pressure (decreased pulmonary flow)
56
What are the three main factors affecting fetal oxygenation?
- Maternal BP
- Maternal oxygenation
- Umbilical cord patency
57
How does the fetus protect itself in the instance of hypoxia?
- ↓ endothelial NO release = vasoconstriction of less important organs.
- ↑ Adenosine accumulation = cerebral vasodilation
## Footnote
**this is a neuroprotective mechanism of the fetus if O2 demand > supply**
58
Why does a fetus have bradycardia in response to hypoxia?
Hypoxia = chemoreceptor stimulation = peripheral vasoconstriction = Vagal response & bradycardia
59
Where is more blood shunted in the event of fetal hypoxia?
DV = ↑O₂ delivery to heart & brain
60
What is the fetal response to **prolonged** Hypoxia (more than a few minutes)?
SNS activates
- catecholamine secretion
- fetal tachycardia
- fetal demise (longer periods)
61
What are the results of **chronic** fetal hypoxia (weeks - months)?
- Fetal growth restriction
- Impaired organ function
- Cardiomyocyte apoptosis
- Fetal demise
62
What are the two ways that fetal heart rate can be monitored?
- External: surface doppler ultrasound
- Internal: fetal scalp electrode
63
External monitoring of uterine contractions is known as ________.
This method of monitoring can determine only what?
TOCO (Tocodynamometer)
Contraction Frequency
## Footnote
**not the strength of contractions**
64
How does internal uterine pressure catheter monitoring (IUPC) differ from external (TOCO) monitoring?
IUPC ccan monitor contraction **frequency** and **strength** (i.e. intrauterine pressure).
65
The fetus depends on the _______ _______ during contractions to maintain oxygenation.
What metaphor for this was using during labor?
Cardiopulmonary reserve (placental reserve)
*Swimmer holding their breath underwater for 30-60 seconds every 2-3 minutes*.
66
What problems with the placenta present a problem with fetal oxygenation that is **unlikely to be reversible**?
- Abruption
- Infarction
- Too small of a placenta
- ↑ placental resistance
67
What are the two problems with the uterus that result in fetal oxygenation impairment?
- Tachysystole (excessive uterine contraction)
- Tetanic Contraction
68
What are potential causes of **tetanic contractions/tachysystole**?
1. maternal stress
2. Pitocin drip too high
3. Drugs (meth, cocaine, stimulants)
69
What are the two problems on the maternal side that result in fetal oxygenation impairment?
- Hypotension
- Hypoxia
70
Uterine contractions are quantified over a ___ minute period and averaged over ____ minutes.
10 minutes : 30 minutes
71
Uterine contractions are measured from the ___________ of one contraction to the beginning of the next.
beginning
72
What is considered a "normal" amount of contractions?
≤ 5 contractions in 10 minutes
73
Tachysystole is defined by > ______ contractions in a 10 minute period.
5
74
How is tachysystole treated?
- Stop Pitocin gtt (if running)
- Nitroglycerin (sublingual or IV): relaxes the uterus
- Terbutaline (β2 agonist)
75
How is a baseline FHR calculated?
Mean FHR rounded to increments of 5bpm during a 10 minute period.
76
What is the normal FHR range?
110 - 160 bpm
77
What defines FHR tachycardia?
Bradycardia?
- Tachycardia: > 160 bpm
- Bradycardia: < 110 bpm
78
What are some common causes of fetal tachycardia originating from issues on the **fetal side?**
- Chorioamnionitis
- Sepsis
- Acute fetal hypoxia
- Fetal heart failure
- Fetal Anemia
79
What is Chorioamnionitis "Chorio"?
Where the mother gets an infection when the amniotic sac ruptures & has been ruptured for a while
80
What are some common causes of fetal tachycardia originating from issues on the **maternal side?**
- Maternal hyperthyroidism
- Maternal fever/infection
- Epi / ephedrine
- β2 agonists (Ritodrine, terbutaline)
81
What are the common causes of fetal bradycardia?
- Hypoxemia (umbilical compression or fetal head compression)
- Hypothermia
- Maternal HoTN
- Maternal hypoglycemia
- Congenital heart block
82
What is the fetus's initial response to hypoxemia?
Bradycardia
83
What are FHR accelerations?
Periods of increased FHR where **bpm increases by 15 and lasts at least 15 seconds**.
84
Is it a good sign if the OB is able to induce fetal heart rate accelerations?
Yes!
*Ex. waking someone up who is sleeping*.
85
What is baseline FHR variability?
* Fluctuations in the baseline FHR
* Irregular in amplitude & frequency
* quantified as amplitude of peak-to-trough in bpm
86
What is the single most important indicator of an adequately oxygenated fetus?
FHR variability (moderate variability = good)
*Visually quantified as amplitude of peak-to-trough in bpm*.
87
What are the levels of FHR variability?
- Absent: range not detectable
- Minimal: detectable by ≤ 5bpm variation
- Moderate: amplitude range 6 - 25 bpm **happy place**
- Marked: range > 25bpm
88
There are a lot of things that can cause decreased or absent FHR variability. Which one is normal and which one do we cause?
- Fetal sleep cycles: fetus has acceleration & variability w/ OB stimulation
- General anesthesia
89
What are some drugs that cause **decreased/absent** variability?
1. Beta Blockers
2. Antenatal Corticosteroids (Betamethasone)
3. Ethanol
4. Decadron
5. BZDs
6. Mg Sulfate
7. Opioids
8. Phenergan
90
What are some common causes of marked FHR variability?
- Fetal stimulation
- Transient hypoxemia (ex. umbilical cord compression during labor)
- Maternal drug use (illicit drugs & stimulants)
91
What type of FHR variability is considered "good"?
92
What are the three types of FHR decelerations?
- Early
- Late
- Variable
*Each of these can also be "prolonged" and/or "severe"*
93
What occurs with FHR as a contraction increases in intensity?
↑ contraction = ↓ FHR
94
What are early decelerations?
Decelerations associated with uterine contraction: benign
* symmetric gradual decrease in FHR w/ return to baseline
* Onset of deceleration to nadir (lowest point) of FHR = / > 30 seconds
* nadir @ peak of contraction
95
What is the physiologic cause of benign early decelerations?
Vasovagal response to fetal head compression (↓CBF) from uterine contraction.
96
Early decelerations are more typical during the _____ stage of labor.
active
## Footnote
*may be r/t cephalopelvic disproportion if in early labor*
97
What type of deceleration is depicted below?
Variable decelerations
## Footnote
*jagged & irregular, U, V, W shape*
98
An abrupt decrease in FHR and an abrupt return to baseline is indicative of _________ decelerations.
variable
99
The onset of variable decelerations to the beginning of FHR nadir is typically _____ seconds.
What does the FHR decrease by?
How long do variable decels last?
< 30 seconds
15bpm or more
greater than 15 seconds, < 2 min
100
What is the most common cause of variable decelerations?
Transient Hypoxemia
- Temporary cord compression (happens during most labors).
- 2ⁿᵈ stage of labor
- Oligohydramnios
101
Frequent variable decelerations or variable decelerations occurring early in labor are often an indicator for what?
Umbilical cord occlusion
*Indicative for operative delivery*.
102
What is oligohydramnios?
Low volumes of amniotic fluid
103
What characterizes severe decelerations?
- FHR < 70 bpm
- ↓ in FHR > 60bpm from baseline
104
Severe decelerations + minimal/absent FHR variability should be concerning for what?
Fetal Hypoxia
105
Late decelerations *can* be benign as long as _______ is present.
FHR variability
106
What type of decelerations are depicted below?
When do they begin?
What is the timing of the onset of decel to the nadir?
Late decelerations
* begin after peak of contraction/contraction is over
* onset - nadir >/= 30 seconds
107
What type of decelerations are depicted below?
Late decelerations
108
What are some non-benign causes of late decelerations?
- Hypoxemia
- Myocardial decompensation/failure
- Chorioamnioitis
- Post-term gestation
- Uterine hyperactivity
- Maternal HoTN/HTN
- Smoking
- Anemia
- Placental abruption/previa
109
How would hypoxemia present alongside late decelerations?
Late decels + fetal tachycardia w/ minimal/absent variability
110
Late decelerations w/ _______ FHR variability is very bad.
absent/decreased
111
What type of decelerations are characterized by decrease in FHR ≥ 15bpm and lasting > 2 minutes (but less than 10 min)?
Prolonged decelerations
112
What are some of the causes of prolonged decelerations?
- Umbilical cord compression
- Prolonged maternal HoTN
- Prolonged maternal hypoxia
- Tetanic uterine contractions
- Prolonged head compression in 2ⁿᵈ stage of labor
113
What type of decelerations are indicated below?
Prolonged decelerations
114
What type of deceleration is depicted below?
Severe decelerations
115
Early, variable, and late decelerations can also be categorized as _______ and _______.
prolonged and severe
116
What type of FHR tracing is exhibited below?
Sinusoidal pattern
* 3-5 cycles/minute
* amplitude range of 5-15bpm
* lasts >20min
## Footnote
**requires OB intervention**
117
What does persistent sinusoidal FHR tracings require?
Obstetric intervention
118
What are common causes of sinusoidal pattern FHR tracings?
- Fetal anemia
- Rh disease (incompatible blood)
- Severe hypoxia
119
Which category of FHR tracings is predictive of normal fetal acid-base status?
Category I
120
What are characteristics of Category I FHR tracings?
- Baseline FHR 110 - 160 bpm
- Moderate variability
- No late/variable decels
- +/- early decels
- +/- accelerations
121
What are the characteristics of Category II of FHR tracings?
- Fetal tachycardia
- Absence of induced accelerations w/ fetal stimulation
- Prolonged decels > 2min but < 10min
- Recurrent late decels w/ moderate variability
122
Are Category II FHR tracings predictive for abnormal fetal acid-base status?
No
123
What are the characteristics of Category III of FHR tracings?
- Sinusoidal FHR pattern
- Absent FHR variability w/ recurrent late decels
- Recurrent variable decels
- Sustained fetal bradycardia
124
Which category of FHR tracings is predictive for abnormal fetal acid-base status?
Category III
125
What are some things that can be done to address Category III FHR tracings?
- Maternal position change
- Discontinue pitocin
- Treat tachysystole
- Surgical delivery
126
What are the five components of the Apgar scoring system?
When is APGAR assessed?
1. HR
2. Respiratory effort
3. Muscle tone
4. Reflex irritability
5. Color
**1 & 5 min**
127
An apgar score range of _____ is considered normal.
8 - 10
128
An apgar score range of ______ is considered moderate impairment.
4 - 7
129
An apgar score range of ______ requires immediate neonate resuscitation.
0 - 3
130
Risk for neonate mortality is __________ proportional to the apgar 1 minute score.
inversely
Lower score = higher risk of mortality
