The influence of coincidence of fetal and maternal QRS complexes on fetal heart rate reliability


Bioelectrical fetal heart activity being recorded from maternal abdominal surface contains more information than mechanical heart activity measurement based on the Doppler ultrasound signals. However, it requires extraction of fetal electrocardiogram from abdominal signals where the maternal electrocardiogram is dominant. The simplest technique for maternal component suppression is a blanking procedure, which relies upon the replacement of maternal QRS complexes by isoline values. Although, in case of coincidence of fetal and maternal QRS complexes, it causes a loss of information on fetal heart activity. Its influence on determination of fetal heart rate and the variability analysis depends on the sensitivity of the heart-beat detector used. The sensitivity is defined as an ability to detect the incomplete fetal QRS complex. The aim of this work was to evaluate the influence of the maternal electrocardiogram suppression method used on the reliability of FHR signal being calculated.

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ΔR :

Detection error of the R wave

ΔT F :

Variation of fetal T RR duration

ΔT M :

Variation of maternal T RR duration

C :

Class of rest component


Coincidence coefficient


Rest component of the fetal QRS complex


Marker of class membership


Percentage of the detected QRS complexes to their overall number


Detection function based on combination of derivative of the FECG


Detection function based on linear filtration of the FECG


Fetal electrocardiogram


Fetal heart rate


Joined time-frequency analysis


Maternal electrocardiogram

N :

Number of all fetal QRS complexes in the signal


Width of fetal QRS complex


Width of the fetal QRS complex after blanking


Width of maternal QRS complex


Signal to noise ratio

T F :

Base value of fetal T RR interval

T M :

Base value of maternal T RR interval

T RR :

Time interval between two consecutive R waves


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Scientific work financed from the State Committee for Scientific Research resources in the years 2004–2006 as a research project No. 3 T11E 01726. Adam Matonia is a fellowship holder of the Foundation for Polish Sciences

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Correspondence to Janusz Jezewski.

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Matonia, A., Jezewski, J., Kupka, T. et al. The influence of coincidence of fetal and maternal QRS complexes on fetal heart rate reliability. Med Bio Eng Comput 44, 393–403 (2006).

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  • Fetal monitoring
  • Abdominal fetal electrocardiography
  • Fetal heart rate
  • Biomedical instrumentation