Lecture 13: Fetal Heart Monitoring

Question 1

What is the pressure sensitive tocodynanmometer transducer useful for measuring?

Answer 1

Measures frequency of contractons; but NOT the strength

Question 2

Using a fetal scalp electrode for internal monitoring should be avoided in which patients?

Answer 2

HIV patients

Question 3

Internal electronic fetal monitoring requires what?

Answer 3

The membranes to be ruptured

Question 4

What is the pH of fetal scalp blood that is considered abnormal (fetal acidosis)?

Answer 4

pH <7.20

Question 5

What is considered normal vs. tachysystole for uterine contractions when monitoring?

Answer 5

• Normal = 5 contractions or less in 10 minutes, averaged over 30 mins
• Tachysystole = >5 contractions in 10 minutes, averaged over 30 mins

Question 6

How do you measure Montevideo units; what do they indicate; what is normal?

Answer 6

• Measure the strength of contractions in a 10 minute period (summed together)
• >200 MVU’s is adequate

Question 7

What is your evaluation of the uterus based on this strip?

Answer 7

Tachysystole

Question 8

When monitoring FHR, at what point on the strip do you assess?

Answer 8

Between contractions

Question 9

What is a normal FHR, tachycardia, and bradycardia?

Answer 9

• Normal = 110-160 bpm
• Tachy = >160 bpm
• Brady = <110 bpm

Question 10

Which FHR is an early sign and which is a late sign of fetal hypoxia?

Answer 10

• Tachycardia is an early sign of hypoxia
• Bradycardia is a late sign of hypoxia

Question 11

What is the most common cause of fetal tachycardia?

Answer 11

Fetal infections –> Chorioamnionitis

Question 12

What is the normal amount of variability in amplitude with FHR?

Answer 12

Moderate (normal) = range of 6-25 bpm

Question 13

What is decreased baseline variability of the FHR an indicator of and when is it an ominous sign?

Answer 13

• Sign of fetal stress, is assoc. w/ hypoxia and acidemia
• Is ominous sign with persistent late decelerations

Question 14

What is considered an acceleration of FHR at <32 weeks and ≥ 32 weeks at gestation?

Answer 14

• <32 weeks: HR ≥ 10 bpm above baselines for 10 sec or more (but <2 mins)
• ≥ 32 weeks: HR ≥ 15 bpm above baseline for 15 sec or more (but <2 mins)

Question 15

What is considered a prolonged acceleration of FHR and how long is considered a change in baseline?

Answer 15

• Prolonged acceleration = ≥ 2 mins
• Change in baseline = ≥ 10 mins

Question 16

What is the cause of early deceleration of FHR and how are they seen on monitor?

Answer 16

• Occur 2’ to head compression; fetal autonomic response to ↑ ICP —> ↓ in HR
• NOT assoc. with fetal distress
• The lowest point of deceleration occur at the same time as the peak of contraction = “mirror image“

Question 17

What is the underlying physiological cause of variable decelerations on FHR monitor?

Answer 17

Secondary to umbilical cord compression

Question 18

How do variable decelerations of FHR appear on monitor; what is the criteria?

Answer 18

• Abrupt ↓ in FHR ≥ 15 bpm lasting ≥ 15 sec and <2 min (looks like big ‘V’)
• Can occur before, during, or after the contraction

Question 19

What is the cause of late decelerations on fetal heart monitoring; why are they a bad sign?

Answer 19

• Caused by uterine placental insufficiency (UPI)
• Most ominous type –> repetitive decelerations usually indicate fetal metabolic acidosis and low arterial pH

Question 20

How do late decelerations appear on fetal heart monitor?

Answer 20

Lowest point of deceleration occurs after peak of the contraction

Question 21

When are prolonged decelerations commonly seen on monitor?

Answer 21

During maternal pushing

Question 22

When is a sinusoidal pattern seen on fetal heart monitoring?

Answer 22

Seen w/ fetal anemia

Question 23

What kind of variability, accelerations, and decelerations may be seen in category I interpretation of FHR pattern?

Answer 23

• Moderate variability
• NO late or variable decelerations
• Accelerations and early decelerations may or may not be present

Question 24

What are the goals and management for category II, recurrent variable decelerations (>50% of contractions)?

Answer 24

• GOAL: alleviate cord compression
• Repositioning amnioinfusion (1st stage of labor)
• Modify pushing efforts: have Mom push w/ every other CTX

Question 25

What are the goals and management of category II, tachysystole, if seen on fetal heart monitoring?

Answer 25

• GOAL: to reduce uterine activity
• Lateral positioning + IV bolus + ↓ oxytocin rate or discontinue
• If no response, give uterine tocolytic (Terbutaline SQ or IV)

Question 26

What seen on fetal heart rate tracing would be considered category III?

Answer 26

• Recurrent late decelerations or variable decels or bradycardia
• Sinusoidal pattern

Question 27

When would you do fetal scalp stimulation and what is a normal response?

Answer 27

• Useful to differentiate fetal sleep from acidosis, when fetal tracing shows reduced variability but no decelerations
• When scalp stimulated: acceleration of 15 bpm lasting 15 sec occurs then the fetal pH value almost always is 7.2 or greater

Question 28

What are 2 potential causes of late decelerations?

Answer 28

• Excessive uterine activity
• Maternal supine HYPOtension