Fetal Monitoring
or
Antepartum Fetal Surveillance
Definition
• To identify the fetuses at risk of intrauterine
hypoxia or even death in utero.
Physiology of Utero placental
circulation
• Normal
• Utero placental insufficiency
Aims
• To identify fetuses at risk of intrauterine
hypoxia so that a permanent injury like
death should be prevented by timely
intervention.
• To identify healthy fetuses among those
suspected to be in problem on clinical
evaluation so that an unnecessary
intervention may be avoided.
Timing of prenatal Assessment
• 1st trimester – diagnosis of pregnancy and
gestational age.
• 2nd trimester – diagnosis of congenial
malformations
• 3rd trimester – assessment of fetal wellbeing
Methods
• Classification
– During pregnancy – Antepartum
– During labour – Intrapartum
INDICATATIONS
Antepartum
1.
2.
3.
4.
5.
Primigravida aged 35 or more.
Multipara aged 40 or more.
Small for date fetus.
Bad obstetrics history.
Pre-existing medical conditions.
> Diabetes mellitus.
> Renal disease.
> Hypertension.
Contd
6. Pregnancy related Diseases:
> PIH.
> rhesus incompatibility.
7. Post date pregnancy.
8. APH.
9. Decreased fetal movements.
HISTORY
• Electronic Intrapartum foetal heart monitoring
was processed by Edward Hon in the late 50’s.
• Caldeyro-Barcia 1968 correlation of intrapartum
changes in foetal heart rate with foetal blood
oxygen and acid base state.
• Hammacher K-1968
FH frequency and condition of foetus and new
born.
…… Contd
• Hon. E.H-1967
5th owrld congress of Gynae & Obs, Sydney
Obstetricians can now identify FHR
characteristics that support the diagnosis of loss
of foetel well being.
• Hon. E.H 1963 & 67
• Introduced scalp electrodes for internal
cardiotocography.
HOW OFTEN
• Once a week
• Twice a week in cases of post dates,
diabetes mellitus and I.U.G.R.
When to start and how often
Clinical conditions
(diabetes Mellitus,
34 weeks
Twice a wk
Cholestasis of pregnancy 36 weeks
Once a wk
Twice a wk
Twice a wk
Once a wk
Ch hypertension ,thyroid
disease, sickle cell disease,
cardiac disease.)
PIH
IUGR
Post dates
on diagnosis
287-293 Days
294 Days
….. Contd
Previous stillbirths
Spron
Discordat twins
RH disease
a wk before
Twice a wk
previous loss/
34 wks.
On diagnosis
Daily
On diagnosis Twice a wk
Individualize Once a wk
Fetal Monitoring predicts more accurately a
healthy baby than a depressed baby.
Methods of Fetal Surveillance
•
•
•
•
Biophysical scoring .
Doppler studies.
Cordocentesis.
C.T.G.
Biophysical Scoring
System.
Foetal Biophysical Scoring System
Manning et Al 1981
Parameters
Breathing movements
score 2
FBM for at least 30
secs in 30 mins
score 0
i.absent FBM
ii.FBM>30 secs.
Gross body movements
3 movements of
baby /limbs in
30 mins
2 or less fetal
movements in
30 mins.
Fetal Tone
active Ext with
return to flex
spinal/Limb
i.no movement
ii.slow Ext with
return to partial
flex.
Foetal Biophysical Scoring System.
Parameters
score 2
score 0
Amniotic
Fluid volume
at least one
pool of AF
of atleast 2cm.
2 episode of accel
of 15 bpm of sets
in 30 minutes
i.no pool
ii.pool<2cm
Foetal Heart
Reactivity
Score of 8 to10 is normal
Score of 4 or less is abnormal
Score of 6 is equivcal
i. less than
2 episode of
acceler of
15 sec.
Modified Biophysical Profile
manning and associates- 1987
Accesses fetus ultrasonically, if four parameters are
normal, they do not perform NST.
• Normal score is 8/8.
• False negative tests < 1 per 1000.
• False positive very high.
Amniotic Fluid Index
(AFI)
Average
16.2 + 5.3 cms.
Oligohydramnios
< 5.0 cms.
Polyhydramnios
> 24.0 cms.
Contraction Stress Test
CLINICAL
FH measurement.
US.
• BPD, FL, HC, AC, FL/AC, ratio.
• AFI.
Doppler.
Amnio.
Cardocentesis.
Fetal Heart Rate Variability
1.
2.
3.
4.
5.
Short term variability
Long term variability
Decreased variability
Acceleration
Decelerations
Early Deceleration
•
•
•
•
•
Benign.
Uniform shape
Onset with onset of contraction
Return to the base line as the contraction ends.
Nadir of deceleration corresponds to the peek of
contraction
• Fail in rate is >20 – 30 BPM.
A Reactive or Normal FHR Trace
• Normal baseline rate 120-160 bpm
• Variability
• Two accelerations of 15 beats above baseline rate
for 15 seconds and no deceleration.
Indications
Intra Partum
1. Breach presentation
2. Trail of labour
3. Clinical signs of fetal distress
4. Prolonged labour
5. Twins
6. Oxytocin in use
7. Epidural anaesthesia
…… Contd
8. Supine hypertension
9. Drugs given to mother.
> Benzodiazepines.
> Tocolytic agents.
> Analgensics
Fetal Acid Base Assessment
Indications
1. Repetitive late deceleration
2. Diminished FHR variability
3. Repetitive severe variable decelerations
4. Atypical variable decelerations.
5. Sinusoidal pattern
6. Persistent non-reactive FHR pattern
7. A clinically confusing FHR pattern.
Contraindications to FBS
1.
2.
3.
4.
5.
Early delivery indicated
FHR trace is reassessing
Changes are due to oxytocin stimulations
Failure to progress in labour
During or soon after a prolonged episode of
bradycardia
6. Spontaneous vaginal delivery is imminent.
Terminology
• Baseline fetal heart rate
FHR 120-160 bpm in between uterine contractions.
• Bradycardia
baseline FHR <120 bpm.
• Trachycardia
baseline FHR of >160 bpm
Bradycardia
(FHR <120 bpm)
•
•
•
•
•
•
Local anaesthetic drugs
Epidural anaesthesia
Post term fetus
Head and umbillical cord compression
Fetal heart block
Severe acidosis.
Trachycardia
•
•
•
•
•
•
•
•
Prematurity
Maternal fever
Maternal hyperthyroidism
Anxiety
Chorioamnionities
Fetal anemia
Chronic hypoxaemia and acidemia
Cardiac arrythmias
Methods of Fetal Surveillance in
Labour
Clinical
• Assessment of fetus size
• Volume and color of AF
• Intermittent auscultation of FHR
Biophysical
• Electronic fetal heart monitoring
Biochemical
• Estimation of PH and blood gas composition from
scalp sampling
Intrapartum fetal surveillance
Purpose is to detect hypoxia and so prevent asphyxia which
may cause either death or permanent neurological
damage, expressed as cerebral palsy, mental deficiency or
a combination of both.
The ability of fetus to withstand the
stress of labor depends therefore on
1. The condition of fetus at the onset of labour.
2. The characteristics of labour :
a. Duration and intensity of contractions.
b. Total duration of labour.
Interpretation of results
PH 7.25 or more =
Normal
PH 7.2 to 7.25
=
Intermediate Range
PH below 7.2
=
Foetal acidosis
Thank You