What causes fetal oxygen supply decrease?
1. reduction of blood flow through maternal blood vessels (i.e. hypertension, hypotension, hypovolemia)
2. reduced oxygen content in maternal blood (i.e. anemia, hemorrhage)
3. reduced fetal circulation (i.e. umbilical cord compression, cord prolapse, placenta separation or abruption)
Normal Uterine Activity pattern?
- contractions occur every 2-5 minutes
- contractions are moderate to strong to palpation or intensity <80 mmHg through IUPC
- at least 30 seconds of rest time between contractions
- resting uterus should be palpable or ~20mmHg by IUPC
What are non-reassuring fetal heart rate patterns?
1. progressive increase or decrease of the baseline rate
2. tachycardia of 160 bpm or more
3. progressive decrease in baseline variability
4. severe variable decelerations (i.e. FHR <60 bpm lasting longer than 30-60 seconds)
5. late decelerations (--> sign of uteroplacental insufficiency)
6. absent or undetected FHR variability
7. prolonged decelerations (>60-90 seconds)
8. severe bradycardia (<70 bpm)
FHR assessment interval - low risk pregnancy
Low Risk Labor
1. First Stage, active phase --> q30 minutes
2. Second Stage --> q 15 minutes
FHR assessment interval - high risk pregnancy?
High Risk Labor
1. First Stage, active phase --> q 15 minutes
2. Second Stage --> q 5 minutes
What is a tocotransducer and what does it measure?
A tocotransducer is the device used to monitor FHR and uterine contractions.
-a tocotransducer can measure the frequency, regularity, and approximate duration of contractions (but not the intensity)
What to use for Internal Monitoring?
Intra-Uterine Pressure Catheter (IUPC) can measure uterine activity (UA) with precision
What is baseline FHR?
-average rate in a 10 minute segment that excludes periodic or episodic changes (i.e. accels and decels)
FHR variability - definition
-irregular fluctuations in the baseline FHR of two cycles per minute or greater
Types of variability (4)?
1. Absent or undetected - fetus is probably dying)
2. minimal variability - greater than undetected by lower than 5 bpm
3. moderate variability - 6-25 bpm
4. marked variability - >25 bpm
What is Tachycardia?
Tachycardia is a FHR baseline of >160 bpm for a duration of 10 minutes or longer. It is usually a sign of fetal hypoxemia.
Causes of tachycardia?
Fetal tachycardia can be caused by maternal or fetal infection, maternal hyperthyroidism or fetal anemia; or in response to drugs like atropine, terbutaline, cocaine, metamphetamines.
What is fetal bradycardia?
FHR baseline < 110 bpm for a duration of 10 minutes or longer. Can be a LATE sign of fetal hypoxia and usually occurs before fetal death.
Causes of fetal bradycardia?
Fetal bradycardia can be caused by prolonged compression of the umbilical cord, placental transfer of drugs like anesthetics, maternal hypothermia, and maternal hypotension.
What are periodic and episodic FHR changes?
Periodic fetal heart rate changes occur in sync with uterine contractions
-Episodic FHR changes occur independent of uterine contractions.
What are accelerations?
Acceleration is a visually apparent abrupt change in FHR above the baseline rate. The increase is >15 bpm and lasts 15 seconds or more, but returns to the baseline less than two minutes from the beginning of the acceleration. Most of the time these occur when there if fetal activity = good sign.
What are decelerations?
Decelerations are a visually apparent change in the FHR below the baseline. They can be benign or nonreassuring.
What are early decelerations caused by?
Caused by fetal head compression. The deceleration usually starts before the peak of the uterine contraction, and returns to baseline when the UC returns to its baseline. Can be seen in the first stage of labor when cervix is dilated 4-7 cm, or in the second stage of labor when mother is pushing.
What are late decelerations caused by? How to treat?
It is associated with UCs but the deceleration begins after the start of the UC, and the lowest point of the decel is after the peak of the UC. This shows that there is uteroplacental insufficiency. May be caused by maternal hypotension, medications, maternal diabetes, placenta previa, abruptio placentae.
How to treat late decelerations?
1. Mother changes position.
2. Elevate mother's legs.
3. Increase IV infusion
4. Stop IV infusion if any.
Variable decelerations: causes?
Umbilical cord compression! Variable decelerations occur any time during the uterine contracting phase.
How to treat variable decelerations?
1. Change the mother's position.
2. Administer oxygen by facemask.
3. During second stage if it happens repeatedly, discourage the mother from active pushing.
Priorities for intrauterine resuscitation.
1. Change the position of the mother (side lying).
2. Increase IV fluid infusion to increase mother's blood volume or elevate her legs.
3. Deliver oxygen via face mask.