OB- Maternal-fetal assessment
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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?
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
Drugs: Terb & parasympatholytic
What is the definition of fetal bradycardia?
-Baseline <120 or 30bpm drop from baseline x 10 min
What are some causes of fetal bradycardia?
- 1. Fetal hypoxia (cord compression, bradyarrhythmias)
- 2. Maternal hypotension/hypothermia
- 3. Drugs (beta-blockers, anesthetics
What is variability of the FHR
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
- -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?
- -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
What are some causes of prolonged decel?
- -Prolonged contraction
- -Fetal--> pelvic exam, FSE/IUPC placement, rapid descent, cord prolapse
- -Maternal--> hypotension, valsalva, hypoxia
Discuss a NST?
- -Requires intact neuro
- -FM triggers accel >85% of the time
- -Healthy term fetus should have 3-4 accels with 20-25bmp accel above baseline, lasting ~40 sec
What can no accelerations in an NST suggest?
- -Sleeping fetus
- -CNS depressants (narcotics/propranolol)
- -Uteroplacental insufficiency (smoking, maternal dx)
What is the criterion for reactive NST?
- -must have 2 15bpm x15sec in 15mins
- -Reassuring for 7 days
What is the criterion for "negative" CST/OCT?
- -3 moderate contxn in 10min, lasting 40-60 with reassuring FHR
- -NO late decels
- - Don't have to see accelerations to be neg
What are some contraindications for CST/OCT?
- 1. risk for premature labor
- 2. premature labor
- 3. mult gestation
- 4. cervical incompetence
- 5. risk for uterine rupture
What is a "positive" CST/OCT?
Fetal distress with contractions--> may see late decels with contraction
What is AFI?
Amniotic fluid index--> sum of vertical diamter of largest pocket in each abd quadrant
What are normal, borderline, oligo & polyhydramnios fluid levels?
- Normal- 8-18
- Borderline- 5.1-8.
- Oligo <or = 5
- Poly > or = 25
Oligohydramnios increases the risk for what 3 things?
- 1. perinatal mortality
- 2. lethal congenital anomaly
- 3. IUGR
What are 4 associated problems with polyhydramnios?
- 1. NTD
- 2. Obstruction of GI tract
- 3. Mult gestation
- 4. fetal hydrops
What does the L/S ratio need to be to have mature lungs?
What does the BPP incorporate?
- 1. NST
- 2. Fetal breathing mvmt
- 3. fetal mvmt
- 4. Tone
- 5. AFI
What do the BPP measures suggest?
- 10--> normal, low risk for chronic asphyxia
- repeat weekly or 2x/wk for DM/>42wks
- 8--> normal, low risk of chronic asphyxia
- repeat weekly unless oligo--> deliver
- 6--> suspect chronic asphyxia
- >36 then deliver
- <36, do amnio & if <2--> repeat BPP
- in 4-6hrs, deliver if amnio
- 4--> deliver >32 wks, repeat if <32wks
- 0-2--> extend test to 120min, if persists then deliver
For the BPP, what is the requirment for fetal breathing movement (FBM)?
-1 episode (>30sec) in 30 min
For BPP, what is the requirement for 2 points for fetal movement?
-3 "discrete" body movements in 30min
For BPP, what is the tone requirement to score 2?
-1 episode of active limb/trunk extension with return to flexion (open/close hand)
For BPP, what is the AFI requirement?
At least 1 pocket = 2x1cm
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