Lecture for Basic Fetal Monitoring

1. ANTEPARTUM
TESTING

2. Antepartum Fetal Assessment
 Fetal movement counting
 Antepartum fetal heart rate testing
 Biophysical profile
 Doppler velocimetry

3. Which test to use?
 Nonstress test
 Biophysical profile, modified biophysical profile
 Contraction stress test
 Low incidence of unexpected fetal death
 Increase in time, cost and inconvenience
 Doppler velocimetry

4. Fetal Movement - Advantages
 Is a daily assessment
 Easy and Non-invasive
 Requires no special equipment
 Mom becomes more in tune with fetus and more
likely to recognize changes in behavior

5. Fetal Movement Counting

6. Purpose of NST
 Determine if:
 Inadequate delivery of oxygen and/or nutrition in
fetal tissue
 Inadequate placenta exchange due to decreased
blood flow, decreased surface area or increased
membrane thickness.
 Inadequate maternal nutrients or oxygen to the
placenta

7. Nonstress Test (NST)
 FHR accelerations reflect CNS alertness and activity
(fetal well being)
 Absence of FHR accelerations may reflect CNS
depression caused by hypoxia, drugs, fetal sleep, or
congenital anomalies.
 The endpoint of the NST is the presence or
absence of FHR accelerations within a specified
period of time

8. Performing the NST
 Position patient in semi-fowler or left lateral tilt (to
minimize supine hypotension)
 Apply external monitors for contraction and FHR
measurement
 Mark tracing when fetal movement is felt or heard
 Fetal sound stimulation may be used to elicit a response.

9. Nonstress Test (NST)
 Accelerations of the FHR occur with fetal
movement, uterine contractions, or in response to
external stimuli.

10. Nonstress Test (NST)
 Target criteria is 2 accelerations of at least 15 beats
per minute (BPM) for 15 seconds in a 20-minute
period
 A healthy fetus < 32 weeks’ gestation may use at
least 2 accelerations of 10 beats per minute (BPM)
for 10 seconds in a 20-minute period
 The more remote from term, the more likely that
nonreactivity will be due to fetal prematurity.

11. Interpreting the NST
 Reactive: Presence of at least 2 accelerations in a 20
minute period
 Non reactive: FHR does not accelerate to meet
criteria or the fetus does not move
 May extend the testing period to 40 minutes or perform a
back-up test.
 Reactive or Nonreactive with decelerations:
individualize management

12. Biophysical Profile (BPP)
 Biophysical activities that can be recorded
with real time ultrasound:
 Fetal movement (FM)
 Fetal tone (FT)
 Fetal breathing movements (FB)
 Amniotic fluid volume (AFV, also known as AFI)

13. Biophysical Profile (BPP)
 Assessment of umbilical blood flow provides
information on blood perfusion of the
fetoplacental unit.
 Activities that become active first in fetal
development (FT, FM) are the last to disappear
when asphyxia arrests all activities.
 Activities that become active later in gestation
(NST, FBM) will be abolished 1st
in cases of
hypoxia and acidosis.

14. Biophysical Profile (BPP) - Scoring
 Each assessment
 When normal: 2
 When abnormal: 0
 Highest Score: 10, Lowest Score: 0
 Accuracy improved by increasing the number of
variables assessed.
 Overall false negative rate: 0.6/1000

15. Biophysical Profile (BPP) - Scoring
 NST: reactive – as described earlier.
 FBM: present - at least 1 episode of at least 30
seconds duration (within a 30 minute period).
 FM: present - at least 3 discrete episodes.
 FT: normal - at least 1 episode of extension of
extremities or spine with return to flexion.
 AFV: normal – largest pocket of fluid greater
than 1 cm in vertical diameter.

16. Purpose of Contraction Stress Test
 A hypoxic fetus will manifest late decelerations
when uterine blood flow is compromised
 Late decelerations correlate with stillbirth, IUGR,
and low Apgar scores.

17. Contraindications to CST
 PROM
 Previous classical cesarean delivery
 Placenta previa
 Incompetent cervix
 History of premature labor in this pregnancy
 Multiple gestation

18. Performing the CST
 Uterine contractions in excess of 30 mm Hg
create an intrauterine pressure that temporarily
stops uterine blood flow.
 A well oxygenated fetus has reserve to tolerate
contractions
 Contractions for CST can be achieved through:
 Oxytocin challenge test (OCT)
 Breast (nipple) stimulation

19. Interpretation of the CST
 Negative: no late decelerations and adequate FHR
recording
 Positive: Late decelerations present with the
majority of contractions (without excessive
uterine activity)
 Equivocal test results: Suspicious,
hyperstimulation, unsatisfactory.

20. Doppler Flow Studies
 In Normal conditions the placenta offers little
resistance to fetal and maternal blood flow, even
during diastole (i.e., between heart beats)
 Useful in evaluation and management of pregnancies
complicated by conditions such as
 Suspected fetal growth restriction
 Red blood cell isoimmunization
 Pre-eclampsia

21. Doppler Flow Studies
 The most commonly assessed Doppler flow
study of the fetus is the umbilical artery
Systolic flow
Diastolic flow
Normal blood flow

22. Doppler Flow Studies
 Waveform may show decreased/absent diastolic
blood flow in the umbilical vessels of a fetus
 Decreased/absent blood flow indicates that the
fetus may not be receiving enough blood,
nutrients, and oxygen from the placenta
Systolic flow No end
Diastolic flow

23. QUESTIONS?