What is the normal blood volume of infant at term delivery?
700-800ml (10-15% of maternal)
What are vascular branches of placenta that project into the intervillous space?
Chorionic villi
Fetal gas exchange is dependent on what 6 things?
1. Intervillous blood flow
2. Placenta surface area
3. membrane permeability
4. O2 tension b/w uterine & umbilical vessels
5. Hgb affinity and concentration
6. Umbilical cord blood flow
Maternal to fetal flow rate is determined by what 2 things?
Maternal BP & anesthesia induction
What are some situations where placental area is reduced?
1. Maternal issues (HTN, DM, vascular dx)
2. Placenta previa, abruptio, infactions
3. intrauterine infection
4. circumvallage placenta
What are some fetal compensation techniques for low O2 tension?
1. Increase fetal CO (3-4x than adult)
2. Increase O2 carrying (HbF)
3. Increased affinitity for O2 (HbF)
4. Anatomical fetal shunts
What is the normal range for fetal heart rate. What the average rate for prior to 30 weeks and average rate after 30 weeks?
Range (120-160)
<30wks--> 160
>30wks --> 140
What should you be worried about if FHR <100 or >160?
1. O2 status
2. Infection
3. Acid-base/electrolye imbalance
Discuss fetal kick counts.
-Begin instruction ~24-28 weeks.
-Tell them to establish the time of day most active (usually evening)
-Perform daily around same time (decide how long it takes to normally get to 10 kicks)
-Call if decrease movement than normal or no movement in 12 hrs
-If decreased fetal movement--> suggest drinking some juice (sugar) or drink something cold, move to a different side and retry kick count
T or F. Intrauterine catheters can give you information on both frequency and intensity?
True (Externol-Toco can only show frequency)
What is the normal resting tone, frequency, duration, and intensity for uterine contraction?
tone- 5-15mm Hg
frequency- 3-5min
Duration- 30-60sec
Intensity- 50-75mmHg (peak contxn)
What is the definition of fetal tachycardia?
-SUSTAINED increase in HR >160 for 10min
(can intermittently go up to 160 and not be tachy because it can be due to fetal activity--> like if you did a couple jumping jacks, your HR would increase briefly)
What are some causes of fetal tachycardia?
Fetal: anemia, hypoxia, cardiac, arrythmia
Maternal: fever, hyperthyroidism
Placenta: amnionitis
Drugs: Terb & parasympatholytic
What is the definition of fetal bradycardia?
-Baseline <120 or 30bpm drop from baseline x 10 min
It's beat to beat changes in the HR. Meaning the HR is just just consistently 140--> changes beat to beat from 140- 145- 152-143-138. Means the fetus is well-oxygenated. If not well oxygenated--> fetus doesn't want to move to conserve oxygen and you'll have less variability
What's the difference between short-term and long-term?
Short term--> no longer really used but is exact beat-beat change
Long term--> rhythmic flucations in FHR (3-5 cycles per min) Easier to determine visually looking a strip.
What is suggested with absent variability?
omnious--> decreased fetal oxygenation or CNS insult or disorder
What does decreased variability suggest?
-Hypoxia, acidosis
-Drugs
-fetal sleep
-congenital anomaly
-extreme prematurity
-fetal cardiac arrhythmias
What are 2 causes of sinusoidal rhythm?
1. Narcotics (morphine/stadol)
2. Rh isoimmunized (impending death--> stat c-section)
What are the 4 types of variability?
1. absent
2. minimal
3. moderate
4. marked
5 sinusoidal
What is the signficance of FHR acceleration?
Reassuring that fetus is well-oxygenated at that moment
-Has to be >15bpm above baseline for 15min
-Associated with fetal movement/contractions
What is the clinical significance for variable decelerations?
-common, usually transient and associated with cord compression (NOT associated with poor outcomes)
-Mild (<30bmp below baseline)
-Mod (<50bpm below baseline)
-Severe (<70bmp, slow return to baseline)
**Abrupt return to baseline is a reassuring sign of good oxygenation despite cord compression
What is the clinical signficance of early decelerations?
-Benign
-Associated with head compression
-FHR is mirror image of contraction or starts decreasing just before contraction visualized
What is the clinical significance of late deceleration?
-Ominous when persistant or uncorrectable. Most worrisome w/ tachycardia and no variability
-Late decels suggest uteroplacental INSUFFICIENCY
What do late decelerations suggest?
-fetal hypoxia, metabolic acidosis
What is the clinical significance of prolonged decel (>90sec)?
-Decreased oxygenation, poor prognosis
-If doesn't return to baseline in 2min--> usually expedite delivery--> forceps/vacumn or c-section