••• Chapter 4^ Antepartum Management and Fetal Surveillance^45
❍ What are the other causes for absence of FHR accelerations?
CNS depressants such as narcotics and phenobarbital and beta-blockers such as propranolol and chronic smoking.
❍ If in 20 minutes of monitoring the NST is nonreactive, what is the next step?
The test can be extended for an additional 20 minutes.
❍ If in 40 minutes of monitoring the NST continues to be nonreactive, what is the next step?
A CST or BPP should be performed.
❍ When is the NST most predictive?
When it is reactive.
❍ What is the perinatal mortality rate associated with a nonreactive NST?
30 to 40/1000.
❍ What is the false-positive rate associated with a nonreactive NST?
75 to 90%.
❍ What percentage of NSTs are nonreactive between 24 and 28 weeks’ gestation?
As high as 50%.
❍ What percentage of NSTs remain nonreactive between 28 and 32 weeks?
15%.
❍ How can vibroacoustic stimulation be utilized during a NST?
Used for a nonreactive tracing in order to promote fetal accelerations. Can decrease time required to obtain reactive
tracing. It has no place in practice with the presence of concerning fetal decelerations.
❍ What is the false-negative rate of a reactive NST (ie, what is the incidence of stillbirth occurring within
1 week of a reactive NST)?
1.9 per 1000.
❍ What is a BPP?
It is the use of real-time ultrasonography to perform an in utero physical examination and evaluate dynamic
functions reflecting the integrity of the fetal CNS, within a 30-minute period.
❍ What five parameters are assessed by the fetal BPP?
- NST.
- Fetal movement.
- Fetal breathing movements.
- Fetal tone.
- Amniotic fluid volume.