## 4 Importance of Electrode Configurations for FECG Measurement
### Electrode Configurations
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline No. & Author & \begin{tabular}{c} **Number of** \\ **Electrodes** \\ **Used** \\ \end{tabular} & **Electrodes Placement** & \begin{tabular}{c} **Parameters**’ \\ **Specification** \\ \end{tabular} & \begin{tabular}{c} **Number of** \\ **Participants** \\ **Time of Data** \\ **Recording (s)** \\ \end{tabular} & **Accuracy** & \
\begin{tabular}{c} **Number of** \\ **Gestation** \\ **Weeks** \\ \end{tabular} &
\begin{tabular}{c} **Proposed Method** \\ **for Extraction of** \\ **ECCG** \\ \end{tabular} \\ \hline
8. & \begin{tabular}{c} **[PERSON] et al.,** \\ 2009 [87] \\ \end{tabular} & 8 & \begin{tabular}{c} **Sampling frequency** \\ **Fetus** \\ \end{tabular} & \
\begin{tabular}{c} **Participants** = 7 \\ **1 kHz Gain = 500** \\ \end{tabular} & 91\% & 37-41 weeks &
\begin{tabular}{c} Weighted \\ **Aveaging of** \\ **MECG segments** \\ \end{tabular} \\ \hline
9. & \begin{tabular}{c} **[PERSON]** \\ **et al.,** **2012 [15]** \\ \end{tabular} & 8 & \
\begin{tabular}{c} **Sampling Frequency** \\ **\(\approx\) 1 kHz** \\ \end{tabular} & - & 91\% & 40 weeks during &
\begin{tabular}{c} Peak detection \\ algorithm \\ \end{tabular} \\ \hline
10. & \
\begin{tabular}{c} **[PERSON]** \\ **et al.,** **2014 [88]** \\ \end{tabular} & 8 & - & - &
\begin{tabular}{c} Participants = 10 \\ **20 min** \\ \end{tabular} & 90\% & 20-28 weeks & - \\ \hline
11. & \begin{tabular}{c} **[PERSON] et al.,** \\ **2014 [68]** \\ \end{tabular} & 10 & - & - & \
\begin{tabular}{c} Participants = 78 \\ **Recording =** \\ **24 s each** \\ \end{tabular} & - & 3 rd trimester &
\begin{tabular}{c} Adaptive R-wave \\ **detection** \\ **algorithm** \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**No. **} & \multirow{2}{*}{**Author**} & \multirow{2}{*}{**Number of Electrodes Used**} & \multirow{2}{*}{**Electrodes Placement**} & \multirow{2}{*}{**Parameters**} & \multicolumn{2}{c}{**Number of Participants and**} & \multirow{2}{*}{**Accuracy**} & \multicolumn{2}{c}{**Number of Gestation**} & \multicolumn{1}{c}{**Proposed Method for Extraction of FECG**} \\  & & & **Used** & & & **Recording (s)** & & **Weeks** & **FECG** \\ \hline \multirow{4}{*}{12} & [PERSON] et al., 2007 [ \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Author**} & \multirow{2}{*}{**Number of Electrodes Used**} & \multirow{2}{*}{**Electrodes Placement**} & \multicolumn{2}{c}{**Number of**} & \multirow{2}{*}{**Accuracy**} & \multicolumn{2}{c}{**Number of**} & \multirow{2}{*}{**Proposed Method**} \\  & & & & & & & & & **Extraction of** \\ \hline \multirow{2}{*}{14.} & \multirow{2}{*}{[PERSON] et al.,1989 [91]} & \multirow{2}{*}{32} & \multirow{2}{*}{**Sampling Frequency = 500 Hz**} & \multirow{2}{*}{Participants = 6 Recordings = 37} & \multirow{2}{*}{-} & \multirow{2}{*}{Between 20 and 40 weeks} & \multirow{2}{*}{Homogeneous volume} \\  & & & & & & & & & \\ \hline \multirow{2}{*}{15.} & [PERSON] et al., 2011 [92] & 32 & - & Sampling Frequency = 1 kHz & - & 91.2\% & Between 35 and 41 weeks & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._In Table 1, the comparison of different electrode placements is listed, which can further be divided into three different ranges, as listed in Table 2[93]. In terms of detection accuracy of FHR, it was noticed from Table 1 that 97.47% was achieved with a four-electrode configuration through a three-step method, including time frequency analysis, complex wavelet, and Heuristic algorithm, at a sampling frequency of 300 Hz, resolution of 12 bits, with a gain of 7800. An accuracy of 91% was obtained with 8-electrode and 32-electrode configurations at a sampling frequency of 1 KHz. Additionally, from Table 1, comparing the sequential method and liner regression method using 12-16 electrodes, an accuracy of 85% was achieved in FHR monitoring.