Fetal monitoring during labour Flashcards
Types of fetal monitoring
Regular intermittent auscultation
Fetal cardiotocography
Fetal heart rate interpretation
Transient changes in FHR
Fetal ECG
Fetal acid-base balance
Regular intermittent auscultation
FHR is monitored every 15 minutes for a 1-minute period after contraction using US or pinard fetal
stethoscope in first stage of labour.
§ FHR is auscultated every 5 minutes or every other contraction in second stage of labour.
§ Contractions are monitored by manual palpation over 10 minutes period to determine frequency.
§ In case mother or fetus are at high risk or with a critical medical condition, all stages are monitored by
continuous electronic fetal monitoring ‘EFM’.
Used in case of fetal growth restriction, oligohydramnios,
meconium-stained liquor, diabetes & pre-eclampsia (critical medical conditions). EFM is only for high
risk labour cases!!
Fetal cardiotocography
§ CTG is a technical means of recording the fetal heartbeat and the uterine contractions during
pregnancy.
It is a non-stress test. The machine monitoring is called a cardiotocograph, commonly
known as an EFM.
§ FHR is calculated using Doppler US transducer applied externally to maternal abdomen.
§ Uterine activity is recorded either with a pressure transducer over the abdomen (less accurate) or by
inserting fluid-filled catheter or pressure sensor into uterine cavity (more accurate).
Fetal heart rate interpretation
Normal heart rate (baseline) is 110-160 bpm.
§ Baseline variability (BV) is the fluctuation in FHR of more than 2 cycles/ minute.
§ BV varies between 5 and 25 bpm due to sympathetic and parasympathetic activity on the heart.
§ BV reduces during fetal sleep phase and hypoxia.
§ FHR with a variability of less than 5 bpm for >90 minutes is abnormal and indicate fetal jeopardy.
Transient changes in FHR
Acceleration: HR >15 bpm for >15sec
and are associated with fetal movements.
Good health sign.
§ Deceleration: ¯ HR >15 bpm for > 15sec
are defined both by their relation to
uterine contractions and by their intensity.
Clinically may be related to hypoxia.
§ Early decelerations: Simultaneous with
uterine contractions and nadir occurs at
its peak. HR <40 bpm. Caused due to
head compression and are physiological.
Seen at late 1st and 2nd labour stage.
§ Late deceleration: Occurs after the contraction and doesn’t return to normal until at least 20 sec after
contraction is completed.
Due to placental insufficiency and severe fetal hypoxia.
§ Variable deceleration: HR falls by more than 40 bpm and usually due to cord compression. It also
suggests worsening hypoxia. Atypical variable deceleration is a type considered to be abnormal!
Acceleration
HR >15 bpm for >15sec
and are associated with fetal movements.
Good health sign
Deceleration
HR >15 bpm for > 15sec
are defined both by their relation to
uterine contractions and by their intensity.
Clinically may be related to hypoxia.
Early decelerations
Simultaneous with
uterine contractions and nadir occurs at its peak. HR <40 bpm. Caused due to
head compression and are physiological.
Seen at late 1st and 2nd labour stage.
Late deceleration
Occurs after the contraction and doesn’t return to normal until at least 20 sec after
contraction is completed. Due to placental insufficiency and severe fetal hypoxia
Variable deceleration
HR falls by more than 40 bpm and usually due to cord compression. It also
suggests worsening hypoxia. Atypical variable deceleration is a type considered to be abnormal!
Fetal ECG
The fetal ECG for changes in the ST waveform along with FHR detects hypoxia and acidemia .
§ ST-analysis ‘STAN’; a device with both standard CTG + ST-analysis, refers to combination of FHR
interpretation and fetal ECG; more accurate in detecting hypoxia and acidemia than CTG only.
§ Scalp (on fetal head) electrode and maternal skin electrode are used. CTG is required!!
Fetal acid-base balance
FHR abnormalities may indicate acidosis but fetal blood obtained from scalp through an aminoscope.
§ Instrument inserted through cervix ~2 cm dilated as mother
lying in a lateral position.
§ Normal pH 7.25-7.35. If abnormality has been detected then
sampling should be repeated within next 30 minutes and
delivery is recommended.
§ If there is sufficient sample, a full blood gas analysis
should be performed as PCo2 with normal base excess may
indicate respiratory acidosis.
Also lactate levels may indicate
fetal acid-base balance.
