Prospective Evaluation of Individual Cardiotocography Parameters in Predicting a Nonasphyxiated Fetus
                     f Obstet Gynecollnd Vol. 53, No. 1 :January/February 2003 Pg 49-52 
Prospective Evaluation of Individual Cardiotocography Parameters 
in Predicting a Nonasphyxiated Fetus. 
Panka j Desai, Ash ish Shah 
Departlllent Of Obstetrics and Gynecology, Medicnl College and S.S.G. Hospital, Baroda. 
Objectives- To assess the efficacy of individual parameters of cardiotocography (CTG) in predicting fetal asphyxia. 
Methods- ln the present prospective study we have analyzed the efficacy of the four basic parameters viz. 1) baseline 
heart rate, 2) beat to beat variability, 3) accelerations and 4) decelerations in individually predicting a non-asphyxiated 
fetus. Results- Eighty percent of babies born to mothers with baseline fetal heart rate< 100 bpm were asphyxiated. The 
same figure precipitously falls down to 2.25% when baseline fetal heart rate was between 110 to 150. This soars to 
68.75% at baseline heart rate> 170 bpm. Beat to beat variability is supposedly the most sensitive of all amongst 
individual parameters. When between 10 - 25 bpm it showed least asphyxia in the newborn (2.95%). On the 
other hand reduced beat to beat variability of< 5 bpm had 78.77% babies asphyxiated. Presence of< 1 acceleration 
of 10 -15 seconds had 80% babies asphyxiated. On the other hand?. accelerations of> 15 seconds in a period of 
20 minutes had the lowest rate of asphyxia i.e. 2.96%. All mothers with variable decelarations have babies born 
asphyxiated. Late decelerations had 67.86% asphyxiated babies. Conclusion- Beat to beat variability with near 
90% specificity and 91% sensitivity turns out to be the most reliable individual parameter in predicting a non-
asphyxiated baby. 
Key words : cardiotocography, baseline heart rate, beat to beat variability, fetal asphyxia 
Introduction In the present prospective study we have tried to 
analyze the efficacy of the four basic parameters of 
Predicting fetal normalcy has always been a challenge 
cardiotocography mentioned above in predicting a 
to the obstetricians. Continuous research and 
non-asphyxia ted fetus. 
introduction of newer technology is being done in the 
obstetric world for the purpose. Amongst all newer Materials and methods 
teclmologies, the two that have withstood scrutiny of 
During 1/7/2000 to 30/6/2001, 184 women in labour 
time are ultrasound and cardiotocography. As 
in whom cardiotocographic monitoring was done 
ultrasound becomes less reliable as pregnancy 
were followed up for their obstetric outcome vis-a-vi~ 
advances, cardiotocography steps in. 
the non-asphyxiated status of the fetus. Standard 
student chi-square test was used for sta ti stical 
The four basic parameters of cardiotocography viz. 1) 
analysis. The sensitivity and specificity of the above 
baseline heart rate, 2) beat to beat variability, 3) 
mentioned parameters in predicting a non-
accelerations and 4) decelerations are compositely 
asphyxiated baby were calculated manually and ther 
used for predicting fetal normalcy. This has 
counter checked with relevant computer software 
consistently given good results. In less than two 
using the SPSS software. 
decades, fetal heart rate monitoring through 
cardiotocography and its different periodic changes 
Baseline heart rate:- In all five subgroups were genera tee 
has achieved broad acceptance as a reliable aid in 
for tabulating baseline heart rate viz. < 100 bpm, 100-
optimizing fetal outcome 1• 
110 bpm, 110-150 bpm, 150-170 bpm, > 170 bpm. A 
this stage of analysis no bias was allowed by callinf 
In a randomized trial involving 13,079 live born 
any one or more of these groups as predictors of feta 
children intrapartum care by electronic fetal heart 
distress. 
monitoring, with scalp sampling when indicated, 
was associated with a 55% reduction in neonatal Bent-to-beat variability : These were divided into fow 
. 2 
se1zures . groups of< 5 bpm, 5-10 bpm, 10-25 bpm, > 25 bpiT 
over a period of 20 min (standard period of recordini-
cardiotocography). 
Paper received 011 28/11/01 ; accepted 011 27/6/02 
Correspondence : Accelerations : These were grouped into four group~ 
Dr. Pankaj Desai viz.,  15 bpm;?. 2 episode of> 15 bpm ove1 
Dandia Bazaar, Baroda- 390 001 a period of 20 minutes. 
4~ 
• 
Pnnknj Desai et nl 
Decelerations Table II: Individual CTG Parameter and Neonatal 
These were divided into four- Outcome: Beat to Beat Variability. 
1. One or no episodes of decelerations in 20 min. 
Heart rate Total Healthy Asphyxiated 
2. Early decelerations of~ 2 visually apparent with Variability 
gradual decrease and return to baseline of fetal 
No No % No % 
heart rate, associ a ted with uterine contraction. 
This was over a period of 20 minutes. The nadir  40 min.) 9 2 22.23 7 77.77 
of declaration was coincident to the peak of 5-10 (>40min.) 38 11 28.95 27 71.05 
con traction. 
10-25 bpm 136 132 97.05 4 2.95 
3. Late deceleration ~ 2 visually apparent with 
>25 0 0 100 
gradual decrease of fetal hea~·t rate beginning 
with the peak of uterine contraction and return Total 184 145 78.8 39 21.20 
to baseline after the contraction was over. This 
Sensitivity 89.74, Specificity 91.03, 
was over a period of 20 minutes. Chi-square value= 104.65, P value= < 0.0001 
4. Variable declarations were labeled as visually 
apparent abrupt decrease in fetal heart rate from Beat to beat variability is supposedly the most 
the baseline. The decrease in fetal heart rate below sensitive of all amongst individual parameters, when 
the baseline was at least 15 bpm lasting from between 10- 25 bpm it showed least asphyxia in the 
baseline to baseline for at least 15 seconds and newborn (2.95%). On the other hand reduced beat to 
lasting for no more than 2 minutes. beat variability of < 5 bpm had 77.77% babies 
asphyxiated. 
Table I: Individual CTG Parameter and Neonatal 
Table III : Individual CTG Parameter and Neonatal '., 
Outcome: Baseline Heart Rate. 
Outcome: Accelerations. 
Baseline heart Total Healthy Asphyxiated 
Rate(bpm) Newborn Newborn Accelerations Total Non- Asphyxiated 
No No % No % Asphyxiated 
No No % No % 
 15 bpm, a meager 2.96% will have 
one of the most popular methods for predicting an asphyxiated baby. Thus presence of accelerations 
absence of asphy>..ia and in turn diagnosis of asphyxia on a cardiotocography pattern have a sensitivity of 
in time. In clinical practice however cardiotocography 90.84 and specificity of 89.74. 
reports arc analyzed comprehensively for all these 
51 
• 
Pnnknj Desai el nl 
In presence of late deceleration 67.86% babies have randomized trial of intrapartum monitoring. 
asphyxia. This is presumed to be occurring as a result Lancet 1989; 2: 1233 - 6. 
of the deoxygenated bolus of blood from the placenta 
3. Leveno K.J ., Cunningham F, Nelson S. A 
being insufficient to support the myocardial action. 
prospective comparison of relative and universal 
So for the period of contraction, there is a direct 
fetal monitoring in 34995 pregnancies. N Eng f 
myocardial hypoxic depression as well as vagal 
Med 1986; 315: 615- 9. 
activity 8 9· . The clinical significance of variable 
4. Krebs H.B., Petress R.E., Dunn L.J. et al. 
deceleration is that it represents a reduction of 
Intrapartum fetal monitoring -1- Classification 
umbilical blood flow 10. This explains all the six babies 
and prognosis of fetal heart r?te pattern. Am f 
born to mothers with variable decelerations being 
Obstet Gynecol 1979: 139; 762 - 2. 
asphyxiated. On the other hand early decelerations 
were not as disturbing as shown in Table IV. 5. Wheeler T., Murrils A.: Patterns of fetal heart rate 
during normal pregnancy: Br. ]. Obstet Cynecol 
Tabulating the sensitivity and specificity of individual 1978; 85: 18 - 27. 
parameters revealed certain obvious facts. Firstly all 6. Thacker S, Stroup D F, Peterson H B: Efficacy and 
these individual parameters have very high safety of intrapartum electronic fetal moni taring: An 
sensitivity of more than 90. However when specificity update. Obstet Gyneco/1995; 86: 613- 20. 
is also considered in judging the normalcy of the fetus 7. Stephanie Penning and Thomas J. Garite: 
then beat to beat variability is the most reliable, though Management if fetal distress: Controversies labour 
others like acceleration and baseline heart rate are a I so Management, 1999; 30: 259- 74. 
very close. Deceleration registers a poor specificity of 
8. Krebs H. B., Petress R.E., Dunn L.J., et al. 
64.1 indicating that this may not be a good parameter 
Intrapartum fetal heart rate monitoring VI, -
for predicting normalcy. How specific is it for 
Prognostic significance of accelerations: Am f 
predicting hypoxia is beyond the purview of the 
Obstet Gynecol 1982; 142: 2305 - 7. 
present paper. 
9. Harris JL., Kruger TR., Parer JT. Mechanism of 
late decelerations in the fetal heart rate. Euro I 
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